From Water Tests
Radon in Water (EPA recommended action levels vary by state) Radioactive radon gas is found in the soil all around us. It is soluble in water, therefore, all groundwater has radon. In homes with private wells, radon enters the home through the water supply and it escapes from the water when the water is flushed, heated, sprayed in showers, dishwashers and washing machines. Radon in water can raise the radon concentration in the air to dangerous levels, and breathing that air over long periods of time can increase the risk of lung cancer.