RO feed pump question

[mol1jb]

Hey all,

For this season I am using a Deer Run 125 hobby RO (the smallest 125 Ray makes). It does not come with a feed pump. I have used it once with my feed tank, which is elevated 4 ft, and had great results. I'm sure I will fine tune it throughout the season to get the most out of it. My question is will a feed pump increase the capability of a RO? Or is my elevated feed tank similar to having a feed pump on a feed tank ground level?

[bowhunter]

The feed pump really won't have any affect on the RO performance. The membrane type, size, condition, sap temperature, sugar content and most important system pressure control the performance. The only issue with no feed pump is that you have to change the filters more frequently to maintain good flow to the RO. As the filter gets fouled the pressure drop across the filter increases and you will suck in air or the pump will start to rattle or cavitate.

[mol1jb]

Thanks for the info.

[maple flats]

In reality a feed pump will have some effect, but not much. On my 250 it has a 1" feed pump that gives about 30PSI feed pressure, I started using an electric feed pump in line before the original feed pump, it changed my typical GPH from 245-255 to 260-270 GPH at 37-38 F. Not much but it now shows 75 PSI on the pressure gauge for the feed pressure, I still run the RO at 270-275 on the high pressure. It basically adds about 15 gal/hr overall

[iby]

I have a procon 5 series with a 3/4hp motor... I don't even bother with a feed pump... I let the procon self-prime and pump... works great.

[Russell Lampron]

Adding a feed pump makes it so that the high pressure pump doesn't have to work so hard. The manufacturer not putting one on it is just a way for them to save money so that they can sell the unit at a lower price.

I've been working on Volvo cars for over 40 years. Volvo had a problem with high pressure fuel pumps cavitating and failing in the late 70's and early 80's. Because the pump was located under the car and not in the fuel tank it had to work too hard to suck the fuel out of the tank. Volvo's solution was to add a high volume low pressure pump on the fuel tank to feed the high pressure pump. That solved the problem.

Add a feed pump to your RO and you'll extend the life of your high pressure pump.

[maple flats]

Besides, a high pressure pump does not like to be run dry, it will fail much sooner.

[Cloverland Maple]

What mechanism do you have on the feed pumps to avoid cavitation or aeration? I want to be able to start the RO and "walk away". I have a low pressure switch between the filter and the ProCon, in addition to other safeguards after the filter, but haven't quite figured it out concerning the feed pump (suction & discharge ends).

[Russell Lampron]

What mechanism do you have on the feed pumps to avoid cavitation or aeration? I want to be able to start the RO and "walk away". I have a low pressure switch between the filter and the ProCon, in addition to other safeguards after the filter, but haven't quite figured it out concerning the feed pump (suction & discharge ends).

My RO has a pressure switch for the feed pump. It has to reach 25 psi for the pump to stay on. When the pressure drops below 25 psi the pump shuts off.

[Cloverland Maple]

My RO has a pressure switch for the feed pump. It has to reach 25 psi for the pump to stay on. When the pressure drops below 25 psi the pump shuts off.

Is this pressure switch on the suction or discharge side of the feed pump? If on the discharge side, do you have concerns about cavitation?

[Wanabe1972]

My low pressure switch is located just before the high pressure pump which is after the feed pump and prefilter. You have to hold the start button until 25 psi for it to stay running and the high pressure pump to be enabled.

[Russell Lampron]

Is this pressure switch on the suction or discharge side of the feed pump? If on the discharge side, do you have concerns about cavitation?

The pressure switch is tapped into the top of the pre filter housing which is on the discharge side of the feed pump. I don't have any concerns about cavitation.

[maple flats]

Cavitation will not be an issue, the feed pump will more than send enough sap to feed the high pressure pump, as long as you have the prescribed pressure after the feed pump.

[mellondome]

Is this pressure switch on the suction or discharge side of the feed pump? If on the discharge side, do you have concerns about cavitation?Cavitation is not am issue with a centrifugal pump (which is what your feed pump should be ) it is an ssue with positive displacement pumps like procom. I do know of people who have had to replace procom pumps due not having a feed pump.