What is the flow rating on your wet/dry? Some of them are not designed to operate with really high flow rates. If that's the case, you could get another pump and set up a closed loop. I know that means more money, but they work great. Another thing is you have a pressure rated pump which isn't necessary for a return pump. The Iwaki WMD30RLT is rated at 600 gph
@ 0' head and has a shut off head of 17'. The same pump in an RLXT (not pressure rated) would give you 1140 gph
@ 0' head and a shut off head of 13'. Another pump you might want to look into is the Blueline. These are very high quality pumps designed by an engineer who worked for Iwaki. The Blueline 30HDX will give you 1110 gph
@ 0' head and a shut off of 13'. The Blueline's, IMO
, are a little quieter than the Iwaki too. Another option would be a Little Giant 3-MDQX rated at 1000 gph
@ 3' head. All these pumps should be within $10 of each other pricewise. An example is the Blueline at about $135.00.