Most drinking water supplies have very low levels of radon. If your home uses the public water supply, any monitoring for radon is carried out by the water provider and you do not need to take any action.
Elevated radon levels can occur in private water supplies that come from groundwater sources such as wells, boreholes or springs. UK Health Security Agency and the Drinking Water Inspectorate have prepared the following advice for householders with private drinking water supplies.
Groundwater used for private drinking water supplies may have elevated radon levels but this occurs mainly in the shaded areas on the indicative UK radon map.
Most of the exposure from radon in a private drinking water supply comes from breathing in radon decay products when they are released to indoor air because of normal household uses of water, such as showering and bathing. Radon exposure from drinking the water is much smaller.
A standard 3-month test for radon in indoor air will identify whether significant levels of radon are being released into indoor air from a private water supply. If the test result is high, it may then be appropriate to test a sample of the water to confirm whether it is the source of radon.
Techniques are available to reduce high levels of radon in private drinking water supplies. After taking action to reduce radon levels in a private water supply, you should re-test both your water supply and home for radon. You should repeat these tests every few years to make sure that levels remain low.
What to do if you are concerned about radon in your drinking water supply
If your water is supplied by a water company, they will take any necessary action. You do not need to do anything.
If your home has a private drinking water supply that is fed from a groundwater source, you should use the online radon map to find out if your home is in a shaded 1 km grid square.
If your home is not in a shaded grid square (if you click on your local grid square, the pop-up message says "All parts of this 1 km grid square are in the lowest band of radon potential") there is a very low risk that your private water supply has high radon levels. You do not need to take any further action.
If your home is in a shaded grid square, and you have a private drinking water supply fed from a groundwater source, there is an increased chance that your water supply may have high radon levels. You should test your home for radon, using a standard 3-month radon test.
If, after following these steps, the result of your radon test is high (above the radon Action Level), it may be that the high radon levels in your home are caused by radon in your private water supply. You should test the water supply in your home for radon. Your local authority may be able to advise you on testing water for radon.
After taking action to reduce radon levels in a private water supply, you should re-test your water supply and home for radon. Repeat the home radon test every five to ten years to make sure that levels remain low.