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.