Question for the RO guys

[Tinkanator2000]

Here's the run down. I have low pH well water, and just recently changed all the filters and membrane on my RO unit. I had installed a 75gpd Filmtec membrane I bought of eBay, but was still getting 17 TDS after the membrane. The feed water only measures about 160. I thought maybe I had a bad membrane, and bought a 50gpd Filmtec from a dealer. I'm still getting 18 TDS after the membrane. This is the same I was getting from my old 100 gpd membrane.


Is there anything that comes to mind that would cause an off brand 100gpd (1 year old, with an 800 flow restrictor), a DOW Filmtec 75gpd ( about 30 gallons of finished RO produced with an 800 flow restrictor), and a new DOW Filmtec 50gpd ( about 10 gallons of finished RO produced with a 550 flow restrictor) to all produce roughly the same TDS water ( about 15-18 TDS with a 160 TDS feed)?

I thought maybe it was my tester, but my DI water reads 0 and separate sources all seem to read ok (I'm going to attempt to calibrate it anyway). I was thinking that it could maybe be caused by a crummy booster pump (it puts out about 55psi and is a fixed pressure off brand pump)?

Lastly, is it common for the pressure gauge needle to bounce quickly when placed just after the booster pump ( I figured it was, as a result of the pumps operation)?



Thanks folks

 

[HurricaneSystem]

I do not think it is common for that needle to bounce, it sounds like you have a lot of air in the system.

I think your RO readings are about normal as the membrane will remove something like 92-98%. So it sounds like that is doing it's job. The rest of your filtration comes from your DI and Carbon stages.

 

[shifty51008]

whats the water pressure going into the membrane?

usually the bouncing around is caused by air in the lines, you can tip the unit upside down to bleed it

 

[Tinkanator2000]

Pressure is about 55 and is generated by the booster pump installed after the initial filters, and just before the membrane.

I assumed the piston action of the booster pump created the bounce.

 

[shifty51008]

I would turn the booster pump up to get pressure around 70psi and that should help. you should be able to lower the TDS to under 5 before the DI if you only have 160 tap.

 

[Tinkanator2000]

I've gone ahead and bought a better booster pump (the CDP880), in hopes that bumping the pressure to a stable 70-80psi will do the trick.