Why return pipe is smaller than the drain pipe?


Premium Member
I keep on reading that people use smaller sized return pipes than the drain pipes. Why is that? I want to use 1.5" drains. Is 1" returns the recommended size according to the drain size?


New member
dont know the recommended return sizes, but the smaller return probably has something to do with the fact that gravity can only pull out a certain amount of water from a certain sized hole....where a pump is forcing water through the pipe, so it can be smaller since the water is being forced and not pulled out w/gravity.


New member
The return is smaller because the pressure can be (will be) higher, since it has a pump pushing it, rather than just gravity.