When I recirculate i do it at low pressure, 300psi, but when I want to get to 15% or higher after recirculating I have to go up higher on the pressure like 425-450, I never go above 450 . That being said I think worrying about Membrane life is overblown. I have had my R.O. 4 years and it still has excellent flow rates and I have never had it professionally cleaned, I soap wash it every other use and at the end of the season I will do soap and acid washes. I have already saved enough money not having it professionally cleaned to buy a new Membrane if need be. The whole idea of the Machine is to save you time boiling, fuel boiling, and to have time to do other more important things. Any expenses incurred running your R.O. Hard if you will can easily be matched by time saved. Just my 2 cents.