Adding a permeate or booster pump to RO System

[USWC]

Greetings,
I have a Rain Soft Ultrefiner UF50T RO System, that I would like to add an apparatus to boost the outlet pressure of the system. I have had the system installed since 2003 and have practiced maintenance to the T (pre/post filters every 6 months - membrane twice since installation). We have never really had an issue with pressure, just that it's not consistent. There is a Expansion tank with 8lbs of pressure on the bladder. Recently added a new fridge that has water/ice in the door. Now I can tell a difference in the water pressure and its consistency, as the fridge is very slow at producing water at the door and hallow ice cubes. I have started investigating pumps for the system and have found myself leaning towards a permeate pump. I like the fact that it''s non electric, so hopefully low maintenance requirements. The problem I am having is I cannot figure out if the RS can accept a permeate pump? My system does not backwash automatically, this is a user initiated process by placing a thumb switch in the center position above the RO MEMBRANE.

So I am now wondering if I should replace the system (watts premiere twist lock 50 gpd with permeate pump) or try and add the pump to the RS. Any thoughts would be appreciated.

[grandam888]

first off, membranes don't need changing very often, only when they have fouled(high tds, no water production), I've seen membranes 10+ years old still in operation.

secondly, please take all pressure readings on bladder tank WITH TANK EMPTY, this is very important for a accurate reading. empty bladder tank, take air pressure 8 psi is fine, the let it fill back up.

before purchasing extra equipment, check to see if you refrigerator has a built in water filter, this will need to be eliminated for better pressure off the bladder tank. If possible just remove it. some fridges automatically bypass the filter when it has been removed, if that's not possible, find the line leading into the fridge filter, cut the line before and after the filter and splice in a union. This line may be 1/4" or 5/16".

after you have done this, retry and see how well the fridge works(with a full tank of water), if its still not that great, then add a Demand pump,here is a link to a page of pumps

a permeate pump shouldn't be used, its more of a pump to improve efficiency of the ro system and not a pressure boosting pump for delivery of product water/ also don't use a "booster" pump, this is meant to up the production rate of an ro system and wont help.

good luck

[USWC]

Thanks for the information. It ended up being the filter inside the refridgerator, once removed everything works as it should.

I am having another issue now with high TDS readings. I cannot understand why it keeps coming back high. I flush the system regularly and find it to be reducing TDS while filling the tank. Once the tank is full TDS begins to increase. With limited information on this system, I am giving far more credence to replacing.

TDS measures 475 from feed, 100 while filling and jumps to between 187-217 depending on when measurements are taken.

Any more ideas?

[grandam888]

I would start by emptying the tank completely, then disconnecting it. Take the tds at the output line coming from the ro to the tank. If its high, wait a few minutes and take it again. If it continues to be high, you may need to replace the membrane.

I would say a minimum rejection rate of 80% would be okay, but 90% is good. So at 450ppm tds I would shoot for 45-50 ppm after the system. Hope this helps.

[USWC]

Thanks again for all your help. I ended up replacing the membrane with OEM (Rainsoft) part. I also noticed while doing the change that Applied Membranes (RainSoft) compatible membranes, are not compatible. The OEM membrane has a tip that protrudes 1' from the bottom of the filter. Also, noticed that DOW FILMTEC makes the OEM membrane (so note to self in the future)...Thanks again for your help.

[USWC]

After further observations TDS continued to increase after flushing. During flush could get a permeate value of 2ppm, w/feed @ 114ppm. After several uses, the TDS would again increase to 26ppm. This was occurring within hours of flushing the system. With some help from RainSoft (RS), was able to determine the brine vs. permeate value was incorrect (very little brine was draining). Found out that there is an adjustment screw within the Fast-flush valve. With a slight adjust, I was able to increase the brine vs. permeate values so that it was about the same (a little more on the brine side). That was on Friday 2 December TDS=2ppm, today Monday 5 December TDS=3ppm. Was very happy the RS tech support was able to assist, and did not insist on a service call = fee.