RO/DI Problems?

[Bill S]

OK, I've hooked up Mikey's old RO/DI (coralife). It has a TDS meter on it. It's been running for about 3 hours. TDS in: 38 TDS out: 69. Somethings wrong? Nitrates out: 5ppm. Nitrates on my other RO/DI: 0 (undetectable). I'm PRETTY sure it's hooked up right. I'm SURE that the "IN" is right before the DI and the "OUT" is right after - it's at the output. Could I be getting some effect from it sitting for 6-8 weeks?

[NaCl_H2O]

You mean the TDS "IN" probe is just before the DI, not the water source, right?

I have had those little IN/OUT TDS meters go bad, I use a handheld HANNA now. Take out the DI cartridge completely and see if it is "contributing" something to the water ... worth a try?

[GaryP]

Are you using the cartridges that were in it when you got it from Mikey? They probably need to be changed out.

[Bill S]

Just talked to Coralife... They said change the RO/DI, AND the membrane. I guess I knew better, but it's POSSIBLE that I let the membrane dry out... They said with their DI resins, a TDS meter is useless. Will always show a high TDS because it releases a detectable sodium compound.

[GaryP]

Hmmm, that's not DI then, its a softener (ion exchange).

[Bill S]

I can't imagine Coralife doing that - that's the cheap way out. They said their "sister company", Kent, has the "other" resin. I'm just going to order this from my guy in Canada. I should have just bought one from him anyway. By the time I replace the membrane and all of the cartridges, I'm at the same number...

[brewercm]

Does it by chance have another cartridge after the DI, they sometimes put one on their that is nothing more than to filter (actually more like treating) the DI'd water for taste purposes.

[Bill S]

No, no extra cartridge. Also, in talking with the tech support, it's likely that I didn't keep the membrane COMPLETELY wet during the couple of weeks it was down. A new 100gpd membrane was $35, so I ordered one of them too. I bought a bunch of filters, & 4 bags of resin - the good kind - for $10 a pop.