Minimum Fluid-o-tech pump size for single 4x40

[crowellsr]

I am looking to switch to a single 4x40 membrane for next season. I currently have a fluid-o-tech pa411 (144gph) with a 1/2hp motor. Will this be sufficient for a single 4x40 (NF90 or XLE)? If I can just switch over the membranes and plumbing it would be a lot more cost effective. The PA411 has a built in bypass and is capable of 250psi

[darkmachine]

I took at peek over at robucket.com they use the following for their single post 4040 build

3/4hp 110v electric motor (can be wired for 240v)
190gph procon stainless pump (with adjustable internal bypass)

I don't know if that is 'just enough' to make it work or there is some wiggle room on psi and hp to make the membrane function efficiently. I went with a 330gph pump for two membranes and a 1hp motor and it worked well, I did a lot of shopping to find a motor that was in my price range that was the right RPM for the pump and had to HP to push it. I originally had a 1/2hp pump with a 125gph procon, it has two 2.5" x 40 membranes, that was a factory machine that functioned fine at 200 psi. Again, not a specialist, just observations on what works, and what others are using.