RO Booster pump pressure on RO unit, too much?

Question:

Hi, I read your reply regarding the pressure the pump puts into an RO unit. The RO unit works best under pressure I understand yet the reply states that there is no real pressure in the system until the flow out is stopped somehow such as with an auto shut off valve. If this is the case what purpose dies the pump serve? My PSI is just 40 and I want to improve the RO unit's performance but I do not wish to break though the maximum 80 PSI stated in the manual. The D-D pump woks at 125PSI. What will the pressure gauge read when the pump is operating?

I hope you can sort out my confusion!!

Thanks so much

Ian

Answer:

Ian
Glad someone reads our FAQ section.

Maximum pressure of 125 psi is only reached in a dead end situation.
Imagine having your finger over the end of a hosepipe blocking the flow. Pressure will build up to the maximum mains pressure. If you allow a small gap between your finger and the hose then much of the pressure is maintained and you get a jet that squirts out a long distance. If you have a gap twice as big then more pressure is lost and the water does not go so far.

The booster pump is like this. With your thumb over the end the pressure will reach a maximum of 125 psi however once you connect the RO Unit some of that pressure is lost as the water flows through the unit.

What pressure you read on the gauge will depend on a number of factors such as the membrane size, the restrictor type and the temperature of the water. I run such a pump but do not run a pressure gauge as I cannot affect the pressure no matter what it reads. The pressure is what the pressure is. It is unlikely in a normal free flow situation that you will have any issues with the pressure exceeding 80psi.

You could exceed this if you blocked both outlets however this would also have the effect of burning out the pump head and so it is not a good idea anyway. If you have a solenoid fitted to the water supply then always make sure that if this closes off that it powers down the pump at the same time.

I have always used a booster pump on my units and it increases the flow regardless of water temperature and improves water quality.

Hope this is clearer now
Cheers
Stuart