sump pit radon seal 4

https://myradonfancostcorner.brightsora.com/posts/understanding-radon-fan-cost-what-homeowners-in-york-pa-should-expect

The sump pit radon seal is that rubbery gasket or foam ring you fit around the sump pump pipe where it enters the pit. It's specifically designed to block the path radon gas uses to seep from the soil through the pit opening and into your basement air. Without it, the sump pit can act like a chimney for radon, pulling the gas right past your pump. A good seal keeps the radon where it belongs—underground—and helps your overall mitigation system work properly.