RO membrane still good to use?

O

Oceanbear1

Amphipod
#1
#1
So i pulled my RO/DI unit out of my garage to start using again. Everything had froze, so went online and bought new filters and a new RO membrane. Everything came into today except the new RO membrane didnt fit, I bought the wrong size. For the heck of it I plugged in my old membrane, even though I thought it would be damaged, and let it run for about an hour. I took a TDS reading, and I was surprised so see it read between 2 and 3 ppm.

so... based off the TDS reading, is the old membrane good to use?
 
jahmic

jahmic

Reef Shark
M.A.S.C Club Member
#2
#2
You need to measure your TDS both before and after the membrane to see if it's good. I was going to try and type out the formula...but got lazy. Instead, click below and enter your TDS in the fields:

http://www.apswater.com/calcs.asp

That link will calculate your membrane's current rejection rate. If the result you get is one or two points below the expected rejection rate of your membrane, it's probably time to replace it.
 
Last edited by a moderator:
jahmic

jahmic

Reef Shark
M.A.S.C Club Member
#4
#4
After all the other filters, but before the membrane. You can disconnect it temporarily and just collect some water into a clean container....or if you have an inline tds meter, just swap the position temporarily.
 
O

Oceanbear1

Amphipod
#7
#7
fun with numbers, before filters my tds is 69. after filters it is 62, after membrane it overed between 1 and 3. With that handy sight it says my efficiency is somewhere betwwen 95% and 98%. The membrane is supposed to be 98%, so I think I'm good for now.

Thanks for the help
 
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