tds in R/O water high?

[tammym1961]

I've been buying my water from a local fish store that state they are selling R/O water. Well I just bought a TDS meter and decided to test the water as I have started having a hair algae problem and it tested at 65. This seems really high to me for R/O water. My tap water is about 160. Could someone tell me what your levels should run.

BTW I just got my new RO/DI unit on Friday so now I can make my own water!! Still would appreciate what my readings should be out of an R/O.

TIA!!

Tammy

[SeanT]

Under 3 usually.
When it creeps above 10 I change filters.

[JHardman]

It all depends on the RO membrane you have.

Assuming everything is configured correctly and functioning correctly...

>75GPD membranes reject ~92%, so with your water you should have a ~13ppm TDS.

<=75GPD membranes reject ~98%, so with your water you should have a ~3ppm TDS.

From your DI stage you should be getting 0ppm TDS. Having a well tuned and efficient RO membrane will save you money too. Checkout this thread for a chart of usage of DI resin based on the TDS entering the DI stage. http://archive.reefcentral.com/forums/showthread.php?s=&threadid=232502