"BenignVanilla" m wrote in
message ...
Do they make check valves for 4 inch PVC?

Get a DWV backflow preventer. It's basically a check valve, though in this
case it's designed to prevent sewage from backup up into your basement when
it floods outside. The inlets and outlets are exactly 4 inches. They're
widely available (in cities where houses have basements) at most retail home
improvement centers.


--
David Pochron