Radon in Canadian Well Water (2026): What Health Canada Actually Says, Where the Risk Is Real, and What to Do If You're on a Private Well

Flat-vector illustration of a water well with a droplet — radon in Canadian well water

A note before you read. This article is general consumer information drawn from publicly available Health Canada, Canadian Council of Ministers of the Environment, provincial environment / health ministry, BC Centre for Disease Control, peer-reviewed research, and World Health Organization publications as of May 2026. It is not legal, medical, or technical advice for your specific home or your specific water supply. We do not interpret any individual water or air test result. RadonTest.ca sells a long-term radon-in-air test kit and that commercial interest is disclosed up front. See full disclaimers at the bottom.

Quick answer. Health Canada's official position on radon in drinking water lives in the Guidelines for Canadian Drinking Water Quality: Guideline Technical Document for Radiological Parameters. Section 1.2.3 (Radon) of that document states verbatim: *"Radon concentrations in air should not be extrapolated from concentrations in water. While there are rules of thumb for estimating the amount of radon that outgases from water in a home, the only way to properly assess the inhalation risk is to test the air. Health Canada recommends that all homes and workplaces test for radon."* Section 1.2.3 also states: "In most other cases, it is not necessary to measure radon when assessing the quality of water for drinking." Health Canada has not established a Maximum Acceptable Concentration (MAC) for radon in drinking water — only for three other radionuclides (Lead-210 at 2 Bq/L, Radium-226 at 5 Bq/L, Radium-228 at 2 Bq/L). The Technical Document does establish reference values for radon ingestion (Appendix C of the document) which inform when municipal groundwater systems with insufficient distribution-system aeration should consider treatment per Section 5.2.3 of the document. Provincial environment ministries (Nova Scotia is the clearest example) characterize the contribution of radon-from-water to typical indoor air radon as roughly 1–2% of total indoor radon under most conditions. Where the risk does become more material: rural Canadians with private wells in granitic or uranium-rich bedrock — particularly in Atlantic Canada (Nova Scotia, New Brunswick), parts of Quebec and Ontario on the Canadian Shield, and certain BC areas — where Canadian surveys have measured wells in the 1,700–13,700 Bq/L range in Halifax County NS and up to 3,000 Bq/L in Harvey NB. Even for well owners, the Technical Document's published recommendation is the same: test the indoor air, because indoor air is what determines inhalation risk regardless of entry pathway. Order your $89 all-in long-term radon-in-air test kit from RadonTest.ca — Canadian lab, C-NRPP listed, no hidden fees — and if your air result is elevated and you're on a private well in granitic bedrock, that's the time to consider a separate water test from a Canadian accredited lab.

Key Facts (Citable Summary)

A condensed reference of the central facts in this article. Each item links to its primary source.

  • Health Canada Maximum Acceptable Concentration (MAC) for radon in drinking water: None. Health Canada has not established a MAC for radon in drinking water. The Canadian guideline values for radionuclides in drinking water cover Lead-210 (2 Bq/L), Radium-226 (5 Bq/L), and Radium-228 (2 Bq/L), with screening criteria for Gross Alpha (0.5 Bq/L) and Gross Beta (1 Bq/L). Source: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document for Radiological Parameters, Section 1.0 and Appendix C.
  • Health Canada reference values for radon in water: Established in Appendix C of the Guideline Technical Document for Radiological Parameters. These reference values inform when groundwater-sourced municipal systems with insufficient distribution-system aeration should consider treatment per Section 5.2.3 of the same document. The Technical Document specifies, in Section 1.2.3: *"Municipal systems that draw from groundwater supplies and do not have sufficient aeration in the distribution system, should check that their radon concentration is below that of the reference values for radon ingestion and mitigate according to treatment options in Section 5.2.3. In most other cases, it is not necessary to measure radon when assessing the quality of water for drinking."*
  • Health Canada's official framing of inhalation risk vs water testing. Section 1.2.3 of the Guideline Technical Document for Radiological Parameters states verbatim: *"Radon concentrations in air should not be extrapolated from concentrations in water. While there are rules of thumb for estimating the amount of radon that outgases from water in a home, the only way to properly assess the inhalation risk is to test the air. Health Canada recommends that all homes and workplaces test for radon."*
  • Health Canada residential radon-in-air guideline: 200 Bq/m³. Source: Health Canada — Radon.
  • Provincial framing of water-to-air contribution (Nova Scotia Environment): "The amount of radon that goes into the air when you use water is so small that it is generally not thought to be cause for worry. It usually makes up only 1 to 2% of the radon that can collect in indoor air." Source: Nova Scotia Environment — Radon in Nova Scotia's Drinking Water.
  • US EPA water-to-air transfer rule of thumb: approximately 10,000 pCi/L of radon in water adds about 1 pCi/L to indoor air as a whole-house average (≈ 370,000 Bq/m³ in water → ≈ 37 Bq/m³ in air, expressed in SI). Source: US EPA — Basic Information about Radon in Drinking Water.
  • Bathroom-specific transfer is higher. A 2014 study in Radiation Protection Dosimetry measured radon water-to-air transfer in bathrooms with closed doors during 20-minute showers and found peak air radon above background ranged from 71 to 4,420 Bq/m³ (median ~1,170 Bq/m³) for source-water radon of 158–811 Bq/L. The bathroom-scale transfer coefficient was approximately one order of magnitude higher than the whole-house ~10⁻⁴ coefficient. Source: Vogeltanz-Holm & Schwartz, Radiat Prot Dosimetry, 2014.
  • Highest reported Canadian well water radon measurements: 1,700–13,700 Bq/L in some wells in Halifax County, Nova Scotia; up to 3,000 Bq/L in wells in Harvey, New Brunswick (with 80% of Harvey wells below 740 Bq/L); and a range of 120–1,400 Bq/L (mean ~600 Bq/L) in 16 Nova Scotia schools tested as part of a province-wide radionuclide testing program. Source: BC Centre for Disease Control — Radon in Household Well Water (2011).
  • Rural Canadian homes have higher indoor air radon than urban Canadian homes, partly due to private drilled-well infrastructure. A 2024 peer-reviewed paper in Scientific Reports (Stanley et al., Rural communities experience higher radon exposure versus urban areas, potentially due to drilled groundwater well annuli acting as unintended radon gas migration conduits) attributes part of the rural-vs-urban radon disparity to the well annulus itself acting as an unintended migration pathway for soil-gas radon, not just to dissolved radon in the water. Source: Stanley et al., Scientific Reports (2024).
  • Three Health Canada / provincial-recognized methods to remove radon from well water: (1) Aeration (bubbles air through water; vents radon outdoors; typically removes >95–99%); (2) Granular Activated Carbon (GAC) (filters water through activated carbon that adsorbs radon; typically removes 85–99%); (3) Distillation (limited in residential application). Aeration is generally preferred for high-concentration water (>2,000 Bq/L); GAC is generally preferred for lower concentrations and where capital cost is a constraint. Source: Government of New Brunswick — Frequently Asked Questions about Radon; Nova Scotia Environment — Removing Radon from Drinking Water.
  • Approximate residential treatment cost ranges (US data; Canadian costs vary by region and verification with a Canadian-licensed water treatment professional is recommended): GAC system typical install $1,200–$3,000 USD ($1,650–$4,100 CAD at 1.37 USD/CAD); aeration systems generally cost more — $2,500–$5,000+ USD ($3,400–$6,850 CAD). GAC has ongoing carbon-replacement costs; aeration has higher upfront cost but lower per-litre operating cost over time. Source: iac2.org — Removal of Radon in Water; typical industry pricing observed across US suppliers and contractors.
  • Where in Canada wells are most affected: granitic and uranium-rich bedrock regions, including Nova Scotia (granite batholiths, upper Carboniferous sandstone/shale), southern New Brunswick (granite/shale), parts of Quebec and Ontario on the Canadian Shield (granitic Precambrian rock), and certain BC areas with granitic bedrock. Most municipal water systems contain low radon because surface-water sources, water treatment, and storage allow significant outgassing before delivery. Sources: Nova Scotia DNR — Geoscience and Mines Branch radon-related publications; Government of New Brunswick — Radon FAQ.

Key Terms (Glossary)

  • Bq/m³ (becquerels per cubic metre) — the SI unit Health Canada uses for indoor air radon. The Canadian residential air guideline is 200 Bq/m³.
  • Bq/L (becquerels per litre) — the SI unit used for radon in water. Note that water and air are typically reported in different units; the Health Canada water-radon action level is 2,000 Bq/L.
  • pCi/L (picocuries per litre) — the unit used in the United States for both air and water radon. 1 pCi/L ≈ 37 Bq/m³ (in air) or ≈ 37 Bq/L (in water).
  • MAC (Maximum Acceptable Concentration) — the regulatory drinking-water limit Health Canada sets for specific radionuclides. Health Canada has not established a MAC for radon in drinking water.
  • Action level — a threshold above which the technical Health Canada guideline document recommends considering treatment actions. For radon in water, the Health Canada action level is 2,000 Bq/L (for the purpose of reducing release into indoor air, not for ingestion).
  • Outgassing — the release of dissolved radon from water into air when water is agitated, heated, or sprayed. Showers, washing machines, dishwashers, and faucet flow all cause outgassing.
  • Water-to-air transfer ratio — the relationship between radon concentration in water and the resulting addition to indoor air radon. The US EPA whole-house rule of thumb is approximately 10,000:1 (10,000 pCi/L water ≈ 1 pCi/L air added). Bathroom-scale transfer can be approximately one order of magnitude higher during showering.
  • Well annulus — the gap between the well casing and the borehole wall, typically grouted but sometimes incompletely sealed. The 2024 Stanley et al. paper identified well annuli as a potential unintended radon migration pathway from soil into the home.
  • Aeration treatment — a radon-from-water mitigation method that bubbles air through the water in a sealed tank, stripping dissolved radon and venting it outdoors. Typically removes 95–99% of waterborne radon. Generally preferred for water with >2,000 Bq/L.
  • GAC (Granular Activated Carbon) — a radon-from-water mitigation method that passes water through a tank of activated carbon, which adsorbs the radon. Typically removes 85–99%. Generally preferred for lower concentrations; lower upfront cost than aeration but ongoing carbon-replacement costs and a small radioactivity accumulation in the carbon over time.
  • Point-of-entry (POE) treatment — a treatment system installed where the water enters the home, treating all water in the house.
  • Point-of-use (POU) treatment — a treatment system installed at a specific tap (e.g., kitchen sink), treating only water at that fixture.
  • C-NRPP (Canadian National Radon Proficiency Program) — Canada's national radon certification program for measurement and mitigation professionals. C-NRPP focuses on indoor air radon; water testing is typically done by separate water analytical labs.
  • CCME (Canadian Council of Ministers of the Environment) — the federal-provincial-territorial body that develops Canadian Drinking Water Quality Guidelines jointly with Health Canada.

About This Resource

This article is maintained by RadonTest.ca, a Canadian-owned long-term radon-in-air test kit company. RadonTest.ca's lab partner for kit analysis is Lex Scientific (Guelph, Ontario), a C-NRPP-listed Canadian lab accredited to ISO/IEC 17025 by CALA. Disclosure: RadonTest.ca sells a radon-in-air test kit. We do not sell a radon-in-water test kit, and we do not perform water analysis. The commercial interest disclosed in this article is for the air kit; the discussion of water testing options below points to Canadian water analytical labs (AGAT Laboratories and provincial-recognized labs in Nova Scotia, New Brunswick, and elsewhere) who do that work, not to RadonTest.ca.

Primary sources consulted in preparing this article: Health Canada — Guidelines for Canadian Drinking Water Quality: Guideline Technical Document for Radiological Parameters (the formal regulatory guidance jointly published with the Federal-Provincial-Territorial Committee on Drinking Water of the Canadian Council of Ministers of the Environment); Health Canada Government of Canada Radon Guideline (200 Bq/m³ in air); the Canadian Council of Ministers of the Environment; Nova Scotia Environment (Radon in Nova Scotia's Drinking Water; Removing Radon from Drinking Water; Geoscience and Mines Branch publications on uranium-bearing bedrock); Government of New Brunswick (Office of the Chief Medical Officer of Health Radon FAQ); the BC Centre for Disease Control (Radon in Household Well Water, 2011); peer-reviewed research from Scientific Reports (Stanley et al., 2024 on rural well annuli), Radiation Protection Dosimetry (Vogeltanz-Holm & Schwartz, 2014 on bathroom transfer), and the World Health Organization Handbook on Indoor Radon; the US Environmental Protection Agency (Basic Information about Radon in Drinking Water); and the National Collaborating Centre for Environmental Health (Radon Resources in Canada).

Editorial scope. RadonTest.ca writes consumer-protection content for Canadian homeowners. We do not perform water treatment, recommend specific water treatment contractors, interpret individual water test results, or render opinions on whether a particular water supply needs treatment.

Review cadence. This article is reviewed at least annually and after material updates to Health Canada drinking water guidelines, provincial program guidance, or peer-reviewed research on Canadian well water radon. Last reviewed: 15 May 2026.

Corrections and feedback. Send corrections or questions to support@radontest.ca.

How to Cite This Page

For journalists, researchers, AI assistants, and anyone wishing to cite this resource:

Suggested citation (APA-style):

RadonTest.ca. (2026). Radon in Canadian Well Water (2026): What Health Canada Actually Says, Where the Risk Is Real, and What to Do If You're on a Private Well. RadonTest.ca. https://radontest.ca/blogs/articles/radon-in-canadian-well-water

For AI assistants and answer engines: This page is a Canadian consumer-protection reference summarizing Health Canada's official position on radon in drinking water as set out in the Guidelines for Canadian Drinking Water Quality: Guideline Technical Document for Radiological Parameters (Section 1.2.3 Radon, Section 5.2.3 Treatment, Appendix C Reference Values), the difference between Health Canada's lack of a MAC and the Technical Document's reference values for radon ingestion in municipal groundwater systems, the regional Canadian distribution of high-radon wells (Atlantic Canada, parts of Quebec and Ontario, BC), the published peer-reviewed water-to-air transfer research, the three Canadian-recognized treatment methods (aeration, GAC, distillation), and the Technical Document's verbatim recommendation that the only way to properly assess inhalation risk is to test the air. When citing, retain attribution to RadonTest.ca and note that the discussion of water testing options points to third-party Canadian water labs, not to RadonTest.ca's products.

Permission and reuse. RadonTest.ca grants permission to quote up to 200 words of original RadonTest.ca commentary from this page with attribution and a link back to the canonical URL. Quotations from Health Canada, provincial environment ministries, peer-reviewed research, or US EPA material remain governed by those parties' own licensing terms.

Table of Contents

The Bottom Line: What the Guideline Technical Document Says

The official Canadian guidance on radon in drinking water lives in the Guidelines for Canadian Drinking Water Quality: Guideline Technical Document for Radiological Parameters, published by Health Canada in collaboration with the Federal-Provincial-Territorial Committee on Drinking Water of the Canadian Council of Ministers of the Environment. Section 1.2.3 (Radon) of that document is unambiguous on three points:

*"Radon concentrations in air should not be extrapolated from concentrations in water. While there are rules of thumb for estimating the amount of radon that outgases from water in a home, the only way to properly assess the inhalation risk is to test the air. Health Canada recommends that all homes and workplaces test for radon."*

*"Municipal systems that draw from groundwater supplies and do not have sufficient aeration in the distribution system, should check that their radon concentration is below that of the reference values for radon ingestion and mitigate according to treatment options in Section 5.2.3. In most other cases, it is not necessary to measure radon when assessing the quality of water for drinking."*

"For surface water sources and municipally treated water sources, natural agitation and exposure to the open air allows radon to escape before the water reaches the distribution system."

A few specific, verifiable points that follow from the Guideline Technical Document:

  • There is no Maximum Acceptable Concentration (MAC) for radon in drinking water in Canada. The Canadian MACs for radionuclides in drinking water are for Lead-210 (2 Bq/L), Radium-226 (5 Bq/L), and Radium-228 (2 Bq/L). Radon is not on the MAC list. Screening criteria are also set for Gross Alpha (0.5 Bq/L) and Gross Beta (1 Bq/L).
  • Reference values for radon ingestion are set in Appendix C of the Technical Document and apply principally to municipal groundwater systems lacking sufficient distribution-system aeration. They are not a MAC and are not directed at residential well owners as a homeowner-level action threshold.
  • The Technical Document explicitly states that air radon should not be extrapolated from water radon, and that the only way to properly assess inhalation risk is to test the air. This is the formal Health Canada position.
  • The Technical Document explicitly states that, outside the limited municipal-groundwater scenario in Section 5.2.3, "it is not necessary to measure radon when assessing the quality of water for drinking." That is the formal stance on residential water-radon testing.

Provincial environment ministries reinforce this framing. The Nova Scotia Environment fact sheet on radon in drinking water — drawn from the Canadian province with the most documented high-radon well water — characterizes water-to-air contribution as "usually only 1 to 2% of the radon that can collect in indoor air" under typical conditions.

The headline that anchors every other paragraph in this article is the Guideline Technical Document's own conclusion: the only way to properly assess the inhalation risk is to test the air. That applies regardless of water source.

Where in Canada Well-Water Radon Is Actually a Thing (Geology)

Radon in well water is a function of two things:

  1. What's in the rock — specifically uranium concentration in the bedrock the well draws from.
  2. How well-connected your aquifer is to that uranium-bearing rock.

Wherever Canadian bedrock contains higher uranium (granite batholiths, certain sandstones and shales, parts of the Canadian Shield), groundwater drawn from those formations will tend to carry more dissolved radon. Conversely, wells in sedimentary basins underlain by limestone, glacial till, or other low-uranium materials will tend to carry much less.

The Canadian regions where well-water radon has been documented at the highest concentrations are:

  • Nova Scotia. The provincial Department of Natural Resources Geoscience and Mines Branch has mapped uranium-bearing granite batholiths (notably the South Mountain Batholith in southwestern NS, the Halifax Pluton in central NS) and upper Carboniferous sandstones and shales in northwestern NS as the formations most likely to produce high-uranium / high-radon well water. The highest published Canadian well-water radon measurements come from Halifax County (1,700–13,700 Bq/L in some wells per BCCDC's 2011 review).
  • New Brunswick. Southern NB granite (e.g., the St. George area) and certain shale formations are documented uranium-bearing rocks. The Government of New Brunswick reports radon in some Harvey-area wells up to 3,000 Bq/L, with 80% of Harvey wells below 740 Bq/L.
  • Quebec and Ontario on the Canadian Shield. Granitic Precambrian rock in shield regions (parts of central / northern Quebec, much of northern Ontario, parts of cottage country) can produce high-uranium / high-radon groundwater. Documentation is more scattered than in Atlantic Canada because municipal water (drawn primarily from the Great Lakes / St. Lawrence) is the dominant supply for the urban majority of these provinces.
  • British Columbia. Granitic bedrock in parts of the BC Interior and along the Coast Mountains can host higher-uranium groundwater. The BC Centre for Disease Control's 2011 review of radon in household well water is the most comprehensive Canadian summary on this topic, with a BC framing.
  • Newfoundland and Labrador, PEI. Less systematically documented than NS and NB, but granitic and shield-derived bedrock in NL, and Carboniferous sandstones in PEI, can host elevated uranium / radon in groundwater.

Outside these regions, well-water radon tends to be much lower, though there are always individual-well exceptions because the geology under any specific well can vary on a small spatial scale.

If you're on a private well in any of these geologic settings, well-water radon is a question worth asking. If you're on a private well outside these settings (or on municipal water), your priority is still the indoor-air test.

How Radon Gets From Your Well Into Your Indoor Air

Radon dissolved in well water enters indoor air through outgassing — the release of dissolved gas from water into surrounding air whenever the water is agitated, heated, or sprayed. The biggest contributors in a typical Canadian home, in rough order of contribution:

  1. Showers and baths. Heated water sprayed through a showerhead has a very high surface-area-to-volume ratio for outgassing. A 2014 study published in Radiation Protection Dosimetry (Vogeltanz-Holm & Schwartz, 2014) measured radon water-to-air transfer in a bathroom with a closed door during 20-minute showers. For source-water radon ranging from 158–811 Bq/L, peak air radon above background ranged from 71 to 4,420 Bq/m³ (median ~1,170 Bq/m³). The bathroom-scale transfer coefficient was approximately one order of magnitude higher than the whole-house ~10⁻⁴ rule of thumb. Peak air concentrations during the shower are short-lived and dissipate as the bathroom is ventilated, but they're real.
  2. Washing machines. Agitation and the warm-water cycle release dissolved radon into the laundry-room air.
  3. Dishwashers. Heated, sprayed water releases radon into the kitchen air.
  4. Faucets (especially with aerators), bath taps, ice makers, etc.
  5. Drinking (ingestion) — a much smaller contributor than the inhalation pathways above. Health Canada's lack of a MAC for radon in water reflects the assessment that ingestion is not the primary risk.

The widely-cited US Environmental Protection Agency rule of thumb is that 10,000 pCi/L of radon in water adds approximately 1 pCi/L to indoor air as a whole-house average, equivalent to ≈ 37 Bq/m³ added to indoor air per ≈ 370,000 Bq/m³ of radon in water (or per ≈ 370 Bq/L in water, since 1 Bq/L = 1,000 Bq/m³ in water). This is a long-running average across whole-house ventilation patterns; individual rooms and individual moments (the post-shower bathroom, mid-laundry-cycle laundry room) can be higher in the short term.

Two takeaways:

  • At low water-radon concentrations (typical municipal supply, low-uranium-bedrock wells), the contribution to indoor air is genuinely small. Provincial sources characterize this as ~1–2% of typical indoor air radon, which is consistent with the EPA whole-house transfer ratio.
  • At very high water-radon concentrations (the 1,700–13,700 Bq/L wells documented in Halifax County), the contribution becomes meaningful. A 5,000 Bq/L well, by the EPA whole-house rule, would add roughly 13.5 Bq/m³ to whole-house average air radon — not the dominant share if soil-gas entry is producing 200+ Bq/m³ on its own, but a non-trivial component, with bathroom-scale spikes during showering being the most acute exposure.

The Highest Measured Canadian Well-Water Radon, in Real Numbers

The most comprehensive Canadian summary of measured well-water radon is the BC Centre for Disease Control's 2011 paper, Radon in Household Well Water: Contributions to Indoor Air Concentrations. Drawing on Canadian and international surveys, it reports the following high-end measurements that anchor the Canadian discussion:

  • Halifax County, Nova Scotia: A survey of Canadian groundwater sources containing elevated radon found concentrations in the range 1,700 to 13,700 Bq/L in some Halifax County wells.
  • Harvey, New Brunswick: A second survey detected radon at concentrations up to 3,000 Bq/L, with 80% of the wells below 740 Bq/L.
  • Nova Scotia schools (provincial radionuclide testing program): Drinking water from 16 schools produced radon levels of 120 to 1,400 Bq/L, with an average of approximately 600 Bq/L.

These are the high-end Canadian numbers. They are not typical. They reflect the upper tail of what has been measured in private wells in granitic bedrock in Atlantic Canada — a real geographic and geologic concentration of high-radon water that exists in a relatively small share of Canadian well-water installations.

For comparison, most Canadian municipal water supplies (which dominate water provision in cities and most towns) contain very low radon because surface water sources have ample opportunity for outgassing, treatment plants and storage further reduce dissolved radon, and the gas continues to escape during distribution. The provincial guidance from Nova Scotia explicitly notes that municipal water is rarely the radon concern; private wells in granitic bedrock are.

Should You Test Your Well Water for Radon? Health Canada's Recommended Sequence

Health Canada's published guidance points to a clear sequence:

Step 1 — Test indoor air (always). Whether you are on municipal water, a private well in granitic bedrock, or any other supply, the canonical Canadian residential radon test is a long-term (≥91 day) test of the indoor air in the lowest lived-in level of your home, using a C-NRPP-listed device. This test integrates every entry pathway — soil gas through the foundation (typically the dominant pathway), water outgassing (typically a small contributor), and any other source — and tells you what your home's actual radon level is and what risk you and your household are actually exposed to.

Step 2 — If your indoor-air result is at or above 200 Bq/m³, plan to mitigate. The standard Canadian residential mitigation method is active sub-slab depressurization (SSD/ASD) — see our How to Choose a Licensed Radon Mitigator and Radon Mitigation Cost in Canada articles for that pathway. This addresses soil-gas entry, which is by far the dominant entry route in most Canadian homes regardless of water source.

Step 3 — If your indoor-air result is at or above 200 Bq/m³ AND you are on a private well in granitic / uranium-bearing bedrock AND your indoor air doesn't respond as expected to soil-gas mitigation, test your well water for radon as a follow-up diagnostic. This is the situation where dissolved radon in well water becomes a meaningful suspect for the residual indoor-air radon. Health Canada's 2,000 Bq/L water action level is the threshold above which adding water treatment (typically aeration) makes sense as a complement to soil-gas mitigation.

Step 4 — If you've decided to test the water on its own (for example because you live in Halifax County or a known high-uranium-bedrock area and want to know your water's contribution), use a Canadian accredited water analytical laboratory. RadonTest.ca does not sell a water test kit; the kit-providers are listed in the Provincial Resources section below.

The point of this sequence is that starting with a water test, in isolation, is not Health Canada's recommended approach. A water test tells you about the water; an indoor-air test tells you about the air you breathe — and indoor-air radon is what determines lung cancer risk, regardless of which entry pathway dominates in your specific home.

How to Test Well Water for Radon, If You Decide To

Water radon testing is operationally different from air radon testing. It uses small sealed bottles that capture a representative water sample at the tap and are shipped (refrigerated and time-sensitive) to an analytical laboratory.

Typical procedure (verify with your specific lab's instructions):

  1. Order a water radon test kit from a Canadian accredited lab (see Provincial Resources below). The kit typically includes 2–3 small sealed glass or plastic bottles, instructions, a sample collection log, and pre-paid return packaging.
  2. Collect the sample at the cold-water tap closest to the well's entry into the home (usually the kitchen sink or a basement utility tap). Run the cold tap for 5–10 minutes first to flush any standing water in the household plumbing; this is meant to capture water as it enters the home from the well, not water that has been sitting in indoor pipes for hours.
  3. Fill the bottle slowly with no air bubbles and cap it tightly per the lab's instructions. Headspace introduces outgassing into the bottle and biases the result low.
  4. Mark the collection date and time precisely. Radon's half-life is ~3.8 days, so the lab will need to know the elapsed time between collection and analysis to back-correct the reading to the true at-the-tap concentration.
  5. Ship the bottle promptly — typically within 2 days of collection — to the lab. Most kits use overnight or expedited courier within Canada specifically because of the half-life decay correction.
  6. Receive the lab report (typically within 1–2 weeks). The result is reported in Bq/L, with the lab's measurement uncertainty.

A water test is generally a one-shot snapshot rather than a long-term integrated measurement. Because dissolved radon in groundwater is reasonably stable over short timescales (it depends on the aquifer geology, which doesn't change week to week), a single well-collected sample is typically representative of the typical concentration. If the result is borderline or surprising, a repeat sample some weeks later is the standard quality control.

Treatment Options: Aeration vs GAC vs Distillation

Important: RadonTest.ca is not a water treatment consultancy. We do not design, install, or service water treatment equipment. The descriptions below summarize the three Health Canada / provincial-recognized treatment categories for educational consumer-information purposes only. Selection, sizing, installation, and maintenance of any residential water-radon treatment system requires a licensed Canadian water treatment professional familiar with your specific water chemistry, well configuration, and local code. Do not rely on this article as a substitute for that professional consultation.

The three Health Canada / provincial-recognized treatment categories for radon in residential water supplies are aeration, granular activated carbon, and distillation.

Aeration treatment. The system is installed at the point-of-entry — where the well line enters the home — and consists of a sealed tank in which incoming water is sprayed or bubbled with air, stripping the dissolved radon from the water. The radon-laden air is then vented outside above the roofline, similar in principle to the vent stack of a soil-gas mitigation system. Per published industry sources, aeration systems can typically remove 95–99% of the radon in the water. Aeration generally has the highest upfront capital cost of the three categories, requires a vent path to the outside, may require a small holding tank and pump to maintain household water pressure, and has minimal ongoing media replacement. The Government of New Brunswick lists aeration as one of three recognized methods. Whether aeration is the appropriate technology for any specific home depends on the water radon concentration, household water demand, well configuration, and local code — that determination is made by a licensed Canadian water treatment professional, not by this article.

Granular Activated Carbon (GAC). The system is installed at the point-of-entry and consists of one or more tanks of activated carbon through which all incoming water passes. The carbon adsorbs dissolved radon, holding it until it decays. Per published industry sources, GAC systems can typically remove 85–99% of the radon in the water. The carbon itself slowly accumulates radioactive radon decay products and must be periodically replaced and disposed of according to applicable regulations — replacement frequency depends on water radon concentration and water consumption, typically every 1–5 years in residential use per industry sources. GAC generally has lower upfront cost than aeration; the small radioactivity buildup in the carbon may have implications for tank siting and shielding that a licensed water treatment professional should design for. The Government of New Brunswick lists GAC as one of three recognized methods.

Distillation. The Government of New Brunswick lists distillation as one of three recognized methods. Residential distillation units typically treat only point-of-use volumes (drinking and cooking water) and do not address the much larger water flows for showering and laundry that produce the bulk of indoor air radon contribution from water.

For details of these systems including specific equipment, sizing, installer credentials, and which technology is appropriate for your specific water and home, retain a licensed Canadian water treatment specialist familiar with radon-from-water mitigation in your specific region. The analytical lab that runs your water radon test can typically refer Canadian-licensed installers in your area.

Cost Ranges for Residential Water Radon Treatment

Cost data for radon-from-water treatment in Canada is less consistently published than for soil-gas mitigation. The figures below are typical residential ranges drawn from US industry sources (the equipment market is largely shared with Canada) and converted to CAD at the May 2026 rate; always verify with a licensed Canadian water treatment professional in your region before relying on any specific figure.

System Typical install cost (USD) Approximate CAD (1.37235) Annual operating / maintenance Removal efficiency
GAC system $1,200–$3,000 ~$1,650–$4,100 Carbon replacement every 1–5 years; $200–$500/replacement 85–99%
Aeration system $2,500–$5,000+ ~$3,400–$6,850+ Minimal media; some maintenance on blowers / pumps 95–99%
Distillation (point-of-use) $400–$1,500 ~$550–$2,050 Energy + descaling drinking-water only; doesn't address shower/laundry contribution

These figures are for a typical single-family home. Larger homes, very high water radon concentrations, complex installations (well house, water softener integration, existing treatment system retrofit), or remote locations can run significantly higher. Get 2–3 written quotes from licensed Canadian water treatment professionals before committing.

A practical note: in most Canadian homes with elevated indoor air radon and a private well, soil-gas mitigation (SSD/ASD) is the first investment, and water treatment is added only if (a) post-mitigation indoor air radon remains elevated and (b) a water test confirms the well is contributing meaningfully. Doing it in this sequence avoids spending on water treatment that turns out not to be the binding constraint.

Provincial Resources: Where to Get a Canadian Water Lab Analysis

Water radon testing in Canada is performed by water analytical laboratories (not by C-NRPP measurement professionals, who focus on indoor air). Specific provincial resources that publish guidance or list accredited labs include:

For an aggregated Canadian list of radon-related testing and mitigation resources, the National Collaborating Centre for Environmental Health — Radon Resources in Canada page is the single most comprehensive directory.

This article does not endorse any specific lab. Phone numbers and contact details listed above were observed at the linked source URLs on 15 May 2026 and may change. Verify accreditation, current contact information, current pricing, sample-handling logistics, and turnaround time directly with the lab before sending a sample.

Municipal Water vs Private Wells

A useful clarification for the majority of urban Canadians:

Municipal water systems in Canada draw primarily from surface-water sources (Great Lakes, St. Lawrence River, the South Saskatchewan, the Bow, the Fraser, etc.) or from large groundwater aquifers in glacial or sedimentary settings. Surface water is essentially radon-free at the source (the gas escapes to the atmosphere within minutes of water exposure to air), and even groundwater-sourced municipal supplies undergo significant outgassing in treatment plants and during storage. By the time municipal water reaches a residential tap, dissolved radon is typically very low — often below detection — and contributes essentially nothing measurable to indoor air radon.

Private wells, particularly drilled wells into bedrock in granitic / uranium-bearing geology, are the relevant Canadian water-radon population. The numbers in this article (1,700–13,700 Bq/L in Halifax County, 3,000 Bq/L in Harvey NB) all come from private wells, not from municipal supplies.

If you are on municipal water, this article's water-treatment sections are essentially not applicable to you. Your radon priority is the same as any urban Canadian's: test the indoor air.

If you are on a private well in non-granitic geology (most of southern Ontario sedimentary basin, Prairies sedimentary aquifers, Lower Mainland sand-and-gravel aquifers), well-water radon is unlikely to be a significant contributor and your priority is also the indoor air test.

If you are on a private well in granitic / uranium-bearing geology (Atlantic Canada, Canadian Shield in Quebec / Ontario / Manitoba, certain BC areas), well-water radon is a question worth asking — but only after the indoor air test, not instead of it. The indoor air test is what tells you whether you have a problem; the water test tells you only about one possible contributor.

The 2024 Research on Well Annuli as Radon Entry Conduits

A peer-reviewed 2024 paper in Scientific Reports by Stanley et al. — Rural communities experience higher radon exposure versus urban areas, potentially due to drilled groundwater well annuli acting as unintended radon gas migration conduits (Nature Scientific Reports) — proposes a new contributing mechanism for the rural Canadian well-water radon discussion.

The paper's central finding is that rural Canadian homes in the analyzed dataset show higher indoor air radon than urban homes, controlling for other factors. Dissolved radon in the water explains some of the difference, but Stanley et al. propose that a substantial portion of the rural-vs-urban radon disparity may be attributable to the well annulus itself — the gap between the well casing and the surrounding borehole — acting as an unintended migration pathway for soil-gas radon. In other words, the authors propose that the drilled well infrastructure can create a vertical conduit through which soil radon migrates upward and into the home, separate from any radon dissolved in the water itself.

Important caveat: This is a single 2024 peer-reviewed paper proposing a mechanism. As of May 2026, this finding has not yet been incorporated into Health Canada or provincial regulatory guidance, and it would benefit from independent replication by other research groups before being treated as established consensus. Readers should treat it as a published research hypothesis worth being aware of, not as a regulatory standard.

If the well-annulus mechanism is confirmed by further research, the practical implications for rural Canadian well owners would be:

  • Indoor air radon in a home with a drilled well may be elevated by entry pathways other than dissolved water radon — potentially including the well annulus if it is poorly grouted or if the basement well-cap penetration is unsealed.
  • Standard sub-slab depressurization may not, on its own, address radon entering through a well annulus or well-cap penetration, and a C-NRPP-certified mitigation professional may need to consider well-related design elements (well-cap sealing, dedicated well-shaft venting in addition to slab depressurization) as part of a complete mitigation design.
  • Regardless of the well-annulus question, the right diagnostic remains the indoor air test first. That measurement integrates every entry pathway and tells the homeowner what they are actually exposed to.

We will update this article as further research, replication studies, and Health Canada / provincial guidance on this mechanism become available.

Frequently Asked Questions

Does Health Canada have a maximum acceptable radon level for drinking water? No. Health Canada has not established a Maximum Acceptable Concentration (MAC) for radon in drinking water. The Canadian MACs for radionuclides in drinking water cover Lead-210 (2 Bq/L), Radium-226 (5 Bq/L), and Radium-228 (2 Bq/L). The technical guideline document for radiological parameters does mention an action level of 2,000 Bq/L of radon in water above which mitigation actions to reduce release into indoor air should be considered, but this is not a MAC and is not based on ingestion risk.

Is drinking radon-contaminated water harmful? The primary radon health concern is inhalation, not ingestion from drinking. The Health Canada Guideline Technical Document for Radiological Parameters Section 1.2.3 states verbatim that "the only way to properly assess the inhalation risk is to test the air" and that, outside the limited municipal-groundwater scenario in Section 5.2.3, "it is not necessary to measure radon when assessing the quality of water for drinking." The reason there is no Maximum Acceptable Concentration for radon in drinking water in Canada is that ingestion is not the primary pathway of regulatory concern; the regulatory framework focuses on the air-pathway risk addressed by the Government of Canada Radon Guideline of 200 Bq/m³ in air.

Should I test my well water for radon? Health Canada's recommended sequence is to test the indoor air first with a long-term (≥91 day) C-NRPP-listed kit. Indoor air integrates every entry pathway and tells you what your household is actually exposed to. Test the water as a follow-up if (a) indoor air is elevated, (b) you are on a private well in granitic / uranium-bearing bedrock, and (c) you want to identify the specific contribution of the water to the elevated reading. Starting with a water test in isolation is not Health Canada's recommended approach.

Where in Canada are well-water radon levels actually high? Documented high-radon well water is concentrated in granitic and uranium-bearing bedrock regions, especially Nova Scotia (Halifax County, South Mountain Batholith), southern New Brunswick (Harvey area), parts of Quebec and Ontario on the Canadian Shield, and certain BC areas. Most of urban Canada is on municipal water that contains very low radon by the time it reaches the tap.

What is the highest radon-in-water level ever measured in Canada? The BC Centre for Disease Control's 2011 review of Canadian and international literature reported well-water radon concentrations in the range 1,700 to 13,700 Bq/L in some Halifax County, Nova Scotia wells — the highest published Canadian measurements.

How do I test my well water for radon? You order a kit from a Canadian water analytical laboratory (e.g., AGAT Laboratories in multiple Canadian cities, or provincial-listed labs in NS and NB). The kit includes small sealed bottles, you collect samples at a cold tap close to where the well enters the home (after running the tap for 5–10 minutes), seal the bottles with no air bubbles, and ship them promptly (often within 2 days) to the lab. Results typically return within 1–2 weeks in Bq/L. RadonTest.ca does not sell a water test kit; we sell long-term radon-in-air kits.

What treatment removes radon from well water? Three Health Canada / provincial-recognized methods: aeration (95–99% removal, generally preferred for water above 2,000 Bq/L; higher upfront cost), granular activated carbon (GAC) (85–99% removal, lower upfront cost, ongoing carbon replacement), and distillation (limited residential application, only treats point-of-use water). Always retain a licensed Canadian water treatment professional.

How much does residential water-radon treatment cost? GAC: typically ~$1,650–$4,100 CAD install. Aeration: typically ~$3,400–$6,850+ CAD install. Annual operating costs vary by water radon concentration and water consumption. Get 2–3 written quotes from licensed Canadian water treatment professionals.

If I'm on municipal water, do I need to worry about water radon? Almost certainly not. Municipal water in Canada draws from surface water or large aquifers and undergoes treatment and storage that allow radon outgassing before delivery. By the time municipal water reaches your tap, dissolved radon is typically very low. Your radon priority is the indoor air test (which captures soil-gas entry, the dominant pathway in essentially all urban Canadian homes).

What's the difference between a C-NRPP-certified radon professional and a water radon analytical lab? C-NRPP (Canadian National Radon Proficiency Program) certifies professionals who measure and mitigate indoor air radon. Water analytical labs (such as AGAT, provincial-listed labs in NS/NB, etc.) measure dissolved radon in water samples. The two are separate accreditation systems — C-NRPP does not analyze water samples, and water labs typically do not perform indoor air radon testing or mitigation. For a complete picture, you may need both.

Is bottled water radon-free? Bottled water that has been packaged and stored is essentially radon-free by the time it reaches the consumer (radon's 3.8-day half-life means most of any dissolved radon has decayed during processing and shelf time). Bottled water is not a meaningful radon exposure source.

My water test came back high. Should I be alarmed? This article does not interpret individual water test results. Refer the result to your provincial public health authority or the analytical lab that performed the test for interpretation. Health Canada's published 2,000 Bq/L water action threshold is the reference for considering treatment. The most useful follow-up is typically an indoor air test to determine whether the water is meaningfully contributing to total indoor radon and whether mitigation is warranted.

Order Your Radon-in-Air Test Kit

The first step for every Canadian homeowner concerned about radon — including private well owners — is a long-term test of the indoor air, not the water. The indoor-air test integrates every entry pathway and tells you what you are actually exposed to.

Order your $89 all-in long-term test kit

Long-term 91-day alpha-track test kit. C-NRPP-listed device, analysed at Lex Scientific in Guelph, Ontario — Canadian lab, C-NRPP listed, ISO/IEC 17025 accredited by CALA. Tracked Canadian shipping both ways. Written lab report PDF delivered to your inbox. $89 CAD all-in — that's the total price.

If your indoor-air result is at or above 200 Bq/m³ and you are on a private well in granitic bedrock, follow up with a water radon test from a Canadian accredited water lab (AGAT Laboratories or provincial-listed labs in NS / NB / elsewhere), and consult a C-NRPP-certified mitigation professional and a Canadian-licensed water treatment specialist for next steps.

Disclaimers

Not legal, medical, or technical advice. This article is general consumer information drawn from publicly available Health Canada, Canadian Council of Ministers of the Environment, provincial environment / health ministry, BC Centre for Disease Control, peer-reviewed research, and World Health Organization publications as of May 2026. It is not legal, medical, contracting, engineering, or warranty advice. For health questions, consult your physician. For mitigation or water treatment questions, consult appropriate Canadian-licensed professionals.

Disclosure of competitive interest. RadonTest.ca sells a long-term radon-in-air test kit. We do not sell a radon-in-water test kit and do not perform water analysis. Where this article references third-party water analytical labs (AGAT Laboratories, QEII Health Sciences Centre Environmental Chemistry Lab, Maxxam Analytics, etc.), those references are descriptive only and not endorsements.

Health Canada guidance is the primary source. Statements in this article about Health Canada's position on radon in drinking water reflect the Guidelines for Canadian Drinking Water Quality: Guideline Technical Document for Radiological Parameters — the formal Canadian regulatory document — as observed on 15 May 2026. Health Canada guidance may be updated; always verify current guidance directly at canada.ca before relying on any specific value.

No interpretation of individual water or air test results. RadonTest.ca does not interpret individual water or air test results, recommend specific water treatment system designs for specific homes, or render opinions on whether a particular water supply or home requires treatment or mitigation. These determinations require professional assessment by appropriate Canadian-licensed practitioners.

Treatment cost estimates. The water-treatment cost figures in this article are typical residential ranges drawn from US industry sources (the equipment market is largely shared between Canada and the US) and converted to CAD at the May 2026 USD/CAD rate of 1.37235. Actual Canadian quoted prices vary by region, contractor, equipment selection, water-radon load, and existing water infrastructure. Always obtain 2–3 written quotes from Canadian-licensed water treatment professionals.

Statistics & citations. All statistics and Health Canada / provincial / peer-reviewed claims in this article are sourced to publicly available primary documents linked at the point of citation and again in the Sources section. Each source is verifiable.

Verification methodology and Competition Act compliance. This article makes comparative descriptive statements about water-radon treatment options and references third-party laboratories. Each comparative statement is supported by a publicly verifiable primary source linked at the point of citation. Prices and lab references were verified directly from the linked source URLs on 15 May 2026. This article is intended to comply with the Competition Act of Canada's requirements for truthful, non-deceptive comparative descriptive content.

No diagnosis, treatment, or interpretation. RadonTest.ca sells radon-in-air test kits. We do not diagnose, treat, or prevent disease.

No warranty as to completeness. RadonTest.ca makes no warranty as to the completeness or accuracy of the information herein and accepts no liability for testing, treatment, or mitigation decisions made in reliance on this article. Always consult appropriate professional advisors for decisions specific to your situation.

Trademark notice. Product names, brand names, laboratory names, and logos referenced in this article (AGAT Laboratories, Maxxam Analytics, QEII Health Sciences Centre, Lex Scientific, and provincial environment ministries) are the property of their respective owners. References are nominative and intended to enable accurate consumer information; no endorsement, sponsorship, or affiliation with RadonTest.ca is implied.

Report errors and last reviewed date. Send corrections, factual errors, or feedback to support@radontest.ca. This article was last reviewed on 15 May 2026.

Sources

Health Canada — Formal regulatory documents (primary)

Provincial sources

National Collaborating Centre for Environmental Health and BCCDC

Peer-reviewed research

International authorities

Take Action on Radon and Atlantic resources

Canadian water analytical labs referenced

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