You should probably look up a calculator for head loss... that S2 probably isn't putting out 1400 GPH. This is the chart that Ecotech gives on their website for the S2. Estimating about 4.5 feet of vertical difference plus maybe a couple of 90 degree elbows, you're looking at roughly 1000 GPH max. It'll drop quick, too, as the pump gets older and when it builds up with detritus.So I talked with Red Sea. The valve isnt meant to close all the way, and they do recommend on the spec sheet a return pump with higher flow then my existing pump. My plan was to upgrade my return eventually but in the meantime I am going to upgrade the valve to a gate valve so I can dial it in to my existing pump and save on any headaches down the road. I'm honestly not sure when I'll upgrade returns. My Ecotech S2 is 1400gph, thats 4x turnover an hour through the sump which honestly is plenty with the amount of intake flow I have.