The Reef Tank banner
1 - 7 of 7 Posts

·
Registered
Joined
·
17 Posts
Discussion Starter · #1 ·
I have a Spectrapure 90 gpd unit.

I just tested my water with a TDS meter and received a reading of 55 ppm. My question is which filter needs replacing? Or should I just replace them all.

Any help would be appreciated.
 

·
Registered
Joined
·
21 Posts
Depends on old everything is. The membranes I think last 2-3 years depending on how much water you make and if you flush it. I would definitely at the very least replace the the first two filters i.e the micron filter and the carbon block, and maybe even the DI resin. Then test and see where your TDS is at. The RO membrane is going to be the most expensive out of them all.
 

·
Shark...fish are friends
Joined
·
5,349 Posts
they say to test your tap water, then pull the line AFTER the RO and see what the RO only TDS is and it should be 90-95% reduction (I forget the exact numbers even though I just got my spectrapure 90gpd tonight and just read it lol). If you aren't getting the 90-95% rejection rate replace the first 3, if you are getting the rejection rate from the RO then its likely the DI needs replaced.
 

·
Registered
Joined
·
4,658 Posts
You need three TDS readings to know for sure.
Tap water TDS, RO only TDS before the DI and final RO/DI TDS.

Sediment and carbon block filters have very little to absolutely nothing to do with TDS, they remove suspended solids, silt, sand, sediment, particulates or big stuff and chlorine. The RO membrane and the DI resin remove the TDS which us in the 0.0001 micron range so you can see why a 1.0 or 0.5 micron sediment filter and carbon block will not remove them, they pass right through.

You need to replace the DI cartridge for sure and if the sediment and carbons are 6 months old or older they will also need replacing since they protect the RO membrane, the expensive and important part. Spectrapure RO membranes should be 98+% rejection rate when new with the Select series being guaranteed to be so in writing. Even at 2-3 years they should still be in the 97-98% range if taken care of properly.
 

·
Premium Member
Joined
·
4,738 Posts
I replace my sediment and carbon filter every 4 months. they are cheap and protect the more expensive components down stream. if you have any tds at the end, you need to do a bit of detective work, as rininger suggested. I believe the spectrapure membranes should be in the 95%-98% rejection rate, but ill have to check the site. it also depends on the membrane. if you are using the regular, batch tested one(id guess youi are) or the individually tested one. then if your ro membrane is functioning correctly and you are still getting tds, then its time to replace the di stage.
 
1 - 7 of 7 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top