cfcw thanks for your reply
Yes production side of the RO system
The pump is nearly five years old. No one has played around with the regulator
I replaced the membranes around a year ago and the regulator with a stainless needle valve. After that the system work fine above 120psi and slowly has decreased to 60psi
checked chlorine zero in system
Flow meters
Product water is at 2.1
Reject water is at 4
flush solenoid valve do you know when it turns on?
You can see the flush solenoid mounted on the RO unit panel. It is a GC solenoid. IIRC the system turns on and runs for about 15 minutes every few hours with the flush valve open. You will notice a low pressure an very high reject when this happens. Someone here is probably more familiar with it than I. You might could just check the hose coming off the downstream side of the solenoid to see if is stuck open.
I'm guessing your TDS is OK? With the slow decrease in PSI, absence of chlorine in the system, and assuming TDS within normal limits it sounds like the pump components might be worn out. But from the beginning your system pressure is lower than the older systems I have seen. The last new RO system I got from them had an operating pressure of about 175 psi. There are new XLE membranes that I use that operate well at lower pressures, but the last I saw Coleman was still using Dow filmtec membranes that were rated for the higher pressures.
Think of it in the simplest terms. That pump is rated to pump at a certain pressure and a certain volume of water. If water can exit the system faster than the pump can replenish it, the pump will not get up to it's rated pressure.
However, if I understand you correctly your gauges are indicating a total output of make plus reject of about 6.1 gpm, so IMO it's most likely the pump. It is much less likely but still possible that the replacement regulator has gone bad prematurely.
