Does anyone know who sells a flapper/weir gate that will act like a check valve but open in very low DP situations?  I'm envisioning one like a pool skimmer flapper/weir but on an industrial scale and quality and instead of floating closed it would sink closed. (i.e bottom of the pool not the surface)  I could make one but I always try to buy things off the shelf first.

I have a large concrete sump with internal concrete walls.  These walls have several large openings to allow flow back and forth to balance out the sump.  I want to add these flappers to 300mm x300mm square openings to only allow flow in one direction but they would have to open on little more than 1-2 ft head pressure.  The water is warm & clean but process water not potable.  I have 10 openings so if one failed it wouldn't be critical but I have very few maintenance oppurtunities to drain the sump so I need something very reliable or I would risk damaging several pumps and forcing an outage.

The reason is for separating out hot and warm streams of water to increase steam savings down stream in secondary processes.

I would be VERY careful about using the headloss curves given by Red Valve. I have used Red Valve duckbill and "TideFlex" check valves and have been burned by excessive headloss.

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