| Re: Do check valves restrict flow? No slight felt or taken, that is why the LOL. It is alwas good to get more info then not and decipher it for ones own application. With the flapper type check vavle if algae builds up around it or a snail is sitting there when it closes do to the reverse flow of water it will not seal completely. With a propper size sump and an anti syphon over flow system you would not need them as stated by MotoReef. |