View Full Version : Question on TDS measurements - UHE 100

03/06/2015, 10:10 AM

Got a curious situation here. When I was running the UHE 100 before (unmodified) - I was getting around 350 PPM TDS into the system and 2 PPM out of the RO Membrane.

I've since added an extra canister (Pre-Filter Assembly, 10in 0.35uM Pleated Sed w/ 1/4in FTP Ports) - replaced the 0.35um Pleated Sed filter with the 0.2 um Zetasorb filter that came with the UHE and installed an additional 0.5 um carbon block inside the UHE (were the sediment filter used to sit).

Now I'm running 350 PPM TDS into the system and getting 7 PPM TDS out of the membrane. That's around double the TDS I would expect to get out of the RO membrane.

I've run approx. 720 total gallons through the system at this point (filled a 90 gallon container 4 times) - so I think it would be too soon for failure.

Can this be explained? Is there any cause for concern with the RO membrane?

03/06/2015, 02:42 PM
Ok - 4 hours later - and 30 gallons total made water - I'm seeing the output TDS after the membrane dropped to 5, then 4 and finally to 3.

03/23/2015, 09:58 AM
Thanks for reporting back. 2% of 350 is 7 ppm, so 98% rejection at 350 is pretty good. Now you are reporting it dropping, to 3, which indicates approximately 99% rejection which is stellar!