Ro tds test

I have an ro unit its giving me a reading of 17ppm that is about 94% better than my tap, but is that good enough for my fish tank?

 

well, depends. if your other option is to use your tap water then yes, its better. if your tds meter ever gets to 1 its recommended that you start changing cartridges. yours seems way over due or there is a serious problem with it.

 

yeah time to change the resin and cartridges. How old is your membranes. Should be zero

 

In many areas of the country, RO alone can't get you to 0 TDS. That's why a lot of people also have to add a DI cartridge to remove the remainder.

 

What inwall said. I'm assuming he only has an RO unit.

 

oh, well, in that case adding a DI only to the unit can be quite cheap. MAXCAP D1 ADD ON KIT
that one for example!

 

I think the MaxCap is designed to be installed upstream of another DI cartridge. This one is better suited to upgrading an RO only system.

 

It is rather old, but never used much until I went to reef. I just bought the tds meter to see where I was at, so you guys think it should be 0, Watts Premier said the unit could remove 99%-75%, then replace but with reef you suggest at a reading of 1ppm I should replace? I would imagine their suggestion is for household use.


Thanks everyone, +K

 

An RO only unit should give you 96-99% removal, depending on the membrane. 94% might be normal for your membrane. I would do some research into it and find out what its rejection rate is. We can't tell you without some more info, like the model of filter, what kind it is, what kind of membrane, GPD rate....

If it's too low, you may not have been doing maintenance (flushing the unit), it may be in a bad spot (needs to be in the dark, in a cool place), or it may be too old. Again, we need more info.

 

RO by itself will never remove everything and get you to a true 0 TDS.
A new RO membrane should give you 96-98% rejection and as it ages that rejection rate may fall and/or the capacity or GPD may drop off. Its usually a combination of both.

Regardless, I would not put 17 TDS in my reef system.

If I might ask, are you testing directly from the membrane or are you pulling it from the drinking faucet and pressure tank. The reason I ask is pressure tanks become full of TDS as the RO cycles on and off to meet pressure demands which leads tohigh TDS creep. You should never use a pressure tank system for reef water for that reason. Its best to let the RO run into a storage container or bucket without the aid of the pressure tank so you get treated water straight from the membrane and not higher TDS water from the tank.

If you tested from the pressure tank try testing from the RO only without the tank. Shut the ball valve on the tank off and try testing unpresurized RO, I'll bet the TDS is significantly lower.

I owned a Watts Premier unit for many years but had them install a tested 75 GPD membrane for me, I live about 5 minutes from their factory. It worked OK but went through DI resin quite fast when I kept the pressure tank. Once I seperated the drinking and reef functions and installed the DI on unpressurized water it was better but stil not in the MaxCapo league which is what I eventually ended up with. My RO only TDS with the Watts system was 13-15, with the MaxCap system the RO only TDS is 5.3 to 6.2, less than half what is was before and DI lasts about 8 times longer.