My boat has a Groco bronze seacock and mounted directly on top of it is a Groco bronze check valve. It feeds a livewell pump and a washdown pump gets its' water from the second fitting on the livewell pump. I boat exclusively in saltwater. I have never had a check valve on my previous boats and don't see the benefit of having a check valve since the livewell pump intake is below water level. I can only think that the spring-loaded check valve can only serve to reduce flow. I trailer the boat. What would the +s and --s be? Opinion/advice??