are the ones at marine depot any better? considering they are 18 bucks each? the only reason i need one is in case my power shuts off. because i have a seaclear tank with a wet dry built in the back, if the pump is shut off the water pressure pushes water back through the little holes where the water comes out, through the hose, and back through the power head filling the back area up, until the water levels are even. this would obviously cause my entire tank to drain about halfway. the check valve would at least be a safety.
oh i think i see what you mean. you mean that if i put the return pipe into the water in the tank that if the power went out it would syphon back to the fuge? if thats what you meant im not worried about that. it is the gravity feed from my tank i am worried about. when my tank is running the back part that contains the wet dry filter remains only about 1/2 full or less. this is where i put the bulkhead. however, if the power goes out, the water pressure from the main tank pushes water back through the line that sends water from the wet dry to the tank, thus filling up the back area until they are at equal levels. the check valve should stop that backflow if power went out and keep the level the same in the tank and it would not fill up the back area so it wouldnt keep draining to my fuge.