My GE Merlin reverse osmosis system works well at 40 psi and above.

The problem is I have about a 6 to 10 psi drop through my acid neutralizer and ion exchanger, so I need to set pump cut-in at 50 psi to get a minimum of 40 psi to the Merlin (depending on fixture usage and flow). I don't really like the 50-70 psi range this produces for the house (all 3/4 and 1/2 CPVC). The 70 psi static pressure after cut-out just makes me nervous.

Now I could buy a booster pump for the Merlin but they are ++$$ more than a CSV. Another option; boosting pressure and isolating the Merlin by installing PRVs to the rest of the house is not practical.

So my plan is to set cut-in at 50 psi (for the Merlin)and cut-out at 60-ish psi (for my peace-of-mind), then set the CSV1Z at 55 psi.

As I see it, the showers will get nice steady pressure, the Merlin will never see less than 40 psi, and the pipes will only see 60 psi after the pump cuts out (static pressure).

I am planning to use a 22 gal Flex-Lite FL-7 so the drawdown at that pressure should be around 4.5 gal for quick pump/CSV activation. Then when the pressure tank fills, the CSV should run full throttle to 55 psi and then throttle to 1 gpm for another 90 seconds or so, cooling the pump. (Its an 8 gpm Aermoter, but it's 20 years old and probably closer to 6 gpm.)

So does using the CSV to set a narrow pressure range seem like a sound idea?