Opinions appreciated: check valve vs anti-siphon holes in overflow returns

[outacontrol]

Originally Posted by gregzz4

Thank you. I saw these awhile back but don't think one will work with my system as the only accessible section of plumbing I could unstall it in is a horizontal run. I would be concerned the weight wouldn't function correctly that way.

The design of them will function best when installed in a vertical pipe, but they should also work on the horizontal aswell. The weight of the stopper is part of the action but alot of the action comes from the water pressure and the valve design. There is a little chamber that deverts some of the back flowing water above the weight, therefore pushing it down.