If the pump you're speaking of is the pressure pump then it does'nt seem like its sized proportionately to the 5-4" membranes. There should be at least one other pump on it. I don't know anything about that type membrane. It does'nt sound like a maple membrane but I'm not sure about that. Four membranes of that size would be sufficient for that many taps. I had the same amount of taps last year with a 3 post machine(xle 4040 membranes) and I kept up alright using a 2.5x10 evaporator. Is it a home built unit? More info and a brand name would help.