Aeration systems are used to reduce the radon concentration in water. The radon is released from the water by bubbling air through the water. The radon is then vented to the outdoors. There is no buildup of radioactive materials when this technique is used. The removal of well over 99% of the radon from the water can be achieved with these units. These units do require the repressurization of the water after it is treated and care must be taken to properly vent the gas. This venting should be done above the roof line just like an air radon system and there should always be an auxiliary fan outside of the living space to provide for the save removal of the gas. Water aeration is considered by the U.S. EPA to be the best available technology for removing radon from well water. Unlike other methods, such as granular activated carbon tanks, aeration does not pose the threat of waste buildup.
The American Association of Radon Scientists and Technologists (AARST) and the American National Standards Institute (ANSI) state that if the radon in water concentration for two samples exceed an action level of 4,000 picoCuries per Liter (pCi/L) then take remedial action to reduce the radon concentration.
Based on a National Academy of Science report (link is external), the EPA estimates that radon in drinking water causes about 168 cancer deaths per year: 89 percent from lung cancer caused by breathing released to the indoor air from water and 11 percent from stomach cancer caused by consuming water containing radon. Radon in the water you drink can also contribute to a very small increase in your risk of stomach cancer. However, this risk is almost insignificant compared to your risk of lung cancer from radon. It is suggested by the EPA that if you have elevated air radon levels and are on a private well, you should have your water radon tested.