When to replace RO membrane?

[OakRaid]

Hi .. Hope someone can help me with this.. I am using a RO/DI system that I have had for years, and hadn't used for a long time.
I replaced the carbon and DI cartridges, but am not sure if I need to replace the membrane? The TDS of my tap water is 378 and the TDS on my RO/DI water is 80 ... So is it time to replace it, or is it still ok? If ok...How high should I let the TDS go before I need to change it?

Thank You!!
Dave

 

[Anonymous]

If the rejection ratio is reasonable with the TDS measurement, then it is fine. Otherwise, it is usually a good idea to replace it once a year or every two years. They usually don't do well after long period of dis-use, since bacteria will breakdown the membrane over time.

The rejection ratio is that amount of RO produced vs the amount of input water. That is, since your TDS ratio is about 1:5 (80:378), you should expect you use 5 gallon of input water for every gallon of RO output water. If it is more than 5 gallon, then your member definitely is not doing its job.

 

[Buckeye Field Supply]

Oak. We need a little bit more information to troubleshoot your system. You report tap water tds of 378 and DI tds of 80.

So for certain your DI resin is shot.

What is the TDS of your RO water? That will allow us to calculate the rejection rate of the membrane.

Russ

 

[Anonymous]

Oh, I missed that. I thought the RO is 80.

After the DI, the TDS should be very, very low, almost not measurable with some TDS meter.