Making Filters Last...

[ramsey]

Sorry for reviving a dead thread but isn't changing the filters because your TDS is 1ppm excessive? I thought anything under 10 TDS is still good. I obviously understand that 0 is better but If I can get a few more months out of my cartridges with no harm to my tank, why should I change them? Just curious.

On a side note, alexdmg has one of your units and it's awesome. I may plumb one into a line in my house and run it into my top off container. I'll look you guys up if I decide to.

[BuckeyeHydro]

Hi Ramsey. Once the output from the DI resin comes up off of 0 or 1, it is dumping materials you used it to capture.

Russ

[ramsey]

So what you're saying is that anything over 0 or 1 and the DI part is not effective? I'm basically just asking what an acceptable TDS is. Mine is 3ppm right now. I read on melevsreef.com that anything under 10ppm is acceptable. That dude has a pretty nice tank too.

[BuckeyeHydro]

As long as the DI water TDS is lower than the RO water TDS, you know it is capturing ions. But as the DI TDS starts to climb, the DI is also dumping certain ions in favor of other ions.

I can't give you a precise number, because we don't know what the ions are in the DI water, but the first to be released by the di are monovalent ions (e.g., ammonia, silicate, nitrate). So unlike tap water at 3 TDS, which would likely be just fine to use, the dissolved solids in 3 TDS DI water are likely not what you'd want in your tank.

I suspect there's no data to support the claim that 10 ppm TDS DI water is ok, other than as you noted, that's what he does and with his particular tap water, his corals, his refugium, etc, etc, it has worked out.

If the issue is that you want your filters to last longer, I'd think about a few other things than leaving the DI resin in longer. For instance:
1. What is the TDS of my RO water?
2. Is my pressure too low?
3. Do I have high CO2 in my tap water eating up my DI resin capacity?

And don't forget that the prefilters (the filter stages that come before the membrane in order of water flow) don't remove dissolved solids. So it may be that your prefilters can stay in longer but just your DI needs to be changed.

Russ