Radon in well water was still elevated after radon in the air was mitigated. Radon in water level was 40,000 pCi/L. (The MassDEP Office of Research and Standards has developed a guideline of 10,000pCi/L for radon in drinking water.)
We installed an AIraider diffused bubble water aeration system, which brought the water radon level down from 40,000 pCi/L to <100 pCi/L