Versatile, Airtight Drain Solution for Radon Mitigation Systems Meet the Volcano Drain, the most adaptable air-tight drain on the market. Designed to seal floor drains and sump covers without sacrificing functionality, it keeps your radon mitigation system running efficiently by preventing vacuum loss. Its smart, flexible design fits perfectly in a 4" opening—or trim it down to fit 3", 2", or even 1.5" drains with ease. Trusted by professionals every day, it's the ideal low-flow drain that also doubles as a convenient, removable access port in sump covers. Clean, simple, and built for performance.