New membrane, high tds

Vanmo92 · Apr 20, 2017

Ive been using a 100gpd systems for just over 3 years now and in that time never seen the tds after the membrane read more than 2, typically its 1. A few weeks ago it jumped to 5 so I ordered a new membrane and swapped it out. After letting it run for an hour and a half the tds was 24 out of the membrane with the new flow restrictor, so out of curiosity I put the old flow restrictor in and the tds dropped to 10. I ran the system without collecting water for a total of now 7 hours and it hasnt dropped below 10. If I put the new flow restrictor back on it jumps back to 24, so ive been using the old one. The model # of the new membrane is identical to the old, so I think the old flow restrictor should be ok. Source water tds is about 200 so 4 would be 98% rejection. I believe 200 is higher than normal due to springtime runoff, which I considered as a possible reason for the initial increase that prompted the change. The DI brings it down the rest of the way but ill be burning through that much faster compared to the 1-2tds ive been at for years. For now I have the old membrane back in and the product water is at 4tds, however I would like to use the new membrane I paid for and my understanding is that its not good to leave them sitting after they've been wet and had the preservative rinsed out, so now Im thinking I swapped it prematurely. Will the tds out of the new membrane eventually come down? I dont remember a "break in" period when my other one was new. Pre filters are only 6 weeks old. Is it normal for the rejection rate to vary by that amount from membrane to membrane?

Salty1962 · Apr 20, 2017

You may have a faulty membrane. It should be "0" after you've run it though 15G of water.

Maximizer · Apr 20, 2017

+1 on faulty membrane but one thing to check would be a rolled o-ring. Have you taken it apart since the install?

Maximizer · Apr 20, 2017

The new membrane will be fine as long as you don't let it dry out, keep it soaking in a tub of water, the cleaner the better

Frop · Apr 20, 2017

Seems like it should be lower.. I'm getting 8-10 TDS from 670 incoming TDS with spectrapure 99%.

Could it be pressure related? Has your pressure change a lot between the two membranes? i think raising my pressure from 60 to 100 drops it a couple TDS (I'd have to check how much but I think up to 4) but the effect slows down also.

Vanmo92 · Apr 21, 2017

O rings look good I sillicon greased them lightly and they are sitting where they should be. My pressure gage is missing a part so im not sure what the pressure is but it seems the same. Other than the product water does seem to be coming out a lot quicker with the new membrane. Thinking about ordering the parts to run this membrane secondarily in series off of my other membrane, especially after seeing yesterday's BRS video. Although if this membrane is defective that would be pointless. Im back to using the old membrane for now getting 3tds after that. 7 lower than the new, all else being the same.