Why return pipe is smaller than the drain pipe?

blkdrgn

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?
 

sir_dudeguy

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.
 

danch

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.
 
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