Rodi help.

EVReef3 · Mar 6, 2013

I've had Rodi problems for the longest time. I bought a used aquamaxx unit a year ago from another member and it never gave me 0 tds. Despite the fact that I changed all the filters and membrane. Last week, I decided to purchase a bulk reef supply 75gpd unit and started it off. I've made about 90 to a 100 gallons of ro water from it. First it was giving me 7 in and 0 out tds. Past two days, the out tds has been between 3 to 4. Everything is new, I don't understand what's going on. The water pressure is 50psi. I'm using cold water. Regular tap water tds is 180
What is there I can do?

dustinhhv · Mar 6, 2013

i went throught the same thing with the typhoon, depending on your tap ppm your Di will run out faster/slower

i personally only get about 40-50 gal before i have to change my Di.. my tap is 700+ppm

caudill187 · Mar 6, 2013

Maybe it just needs to break in? 3 or 4 TDS may be a measurement error?

EVReef3 · Mar 6, 2013

I have a handheld tds as well as the inline that came with the Rodi. It's still reading 3.

moreef · Mar 6, 2013

I seem to have same problem. Are you testing out of your mixing container or a clean cup/glass? 3/4 isn't all that bad but I guess it shoud read zero.

fragmatic · Mar 6, 2013

Did you install the membrane into the canister yourself? Sometimes they need to be pushed in deeper. You must push the membrane all the way into the canister and it can be a hard push. If you don't the pre-filtered water bypasses the membrane and goes into the DI resin with far too much tds. It uses up the resin in a hurry, and your water will quickly read about like yours does in about 40 to 60 gallons. If this is the case your membrane is good but you may need to replace the resin in the DI canister.

unforgettably.... I know from experience.

moreef · Mar 6, 2013

sorry I just saw that you have an inline tds. I added a 2nd di filter to mine. Not sure if this is even a good idea or not but im now finally reading 0.

EVReef3 · Mar 7, 2013

Everything was already installed inside the unit. I can open it and see if the membrane can be pushed in some more. If that doesn't fix the problem, should I contact brs? I'm not sure how they stand behind their products. I'm shooting for 0tds because of algae problem from old unit.

AZDesertRat · Mar 7, 2013

Not all DI resins are equal. I am very particular about resins, you never know what resin brand or blend they are using, if it is fresh or not, has been stored, packed and shipped properly etc.
You estimate you have made 90-100 gallons of RO/DI water so it may just be that your resin is exhausted and in need of replacement.
Right now, what are your tap water TDS, RO only TDS and final RO/DI TRS numbers taken directly from the unit, not out of a storage reservoir or container? Have you checked your waste ratio to ensure it is close to between 3:1 and 4:1? What handheld TDS meter do you use and have you kept it clean and capped and checked its calibration or at least confirmed it reads 0 TDS with distilled water?

Your RO rejection rate is 96% using your 180 and 7 numbers so is acceptable but could be better since the membrane is new. I am not a fan of dry untested RO membranes, you get what you get so I prefer to buy treated and tested membranes with a guaranteed 98+% rejection rate. The extra 2% doubles the life of your DI resin without doing anything else.

AlexAquaFX · Mar 9, 2013

I'm with AZ on this one. Make sure you're getting fresh "Virgin" DI resin, that is Nuclear (Or Semiconductor at the minimum) grade, and stored/shipped correctly. Also like he said, wet tested membranes are a better bet! Make sure your meter is reading correctly, and if you are still getting TDS breakthrough, then your DI resin is most likely exhausted.