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reilly2524
09/22/2017, 01:26 PM
I'm in the final steps of setting up my first reef tank and right now in the process of making my rodi water. My problem is I'm burning through my DI resin, I've made about 60 gallons and I'm already about halfway through my resin canister(see picture). The tds from the ro is 2 so I'm not sure why the resin is getting used up so fast. I am using well water but I don't think co2 is the problem because when I tested the ph and alk, in order to do a calculation that would determine how much co2 is in the water, my alk from the ro is about .2dkh and the ph is 7.3 which would but the co2 at less then 1ppm. Any ideas?

ktownhero
09/22/2017, 01:29 PM
Are you flushing your RO membrane before running it through the DI? If you don't, what happens is that the first minute or so that goes through the DI canister will have high TDS until the RO membrane is flushed out. This has a dramatic impact on the life of the resin. You can avoid it going through the DI canister by using a flush valve for a minute or so... Once you see your RO reading is down to an acceptable level, then you close the flush valve and open up the DI canister and let it run.

JTL
09/22/2017, 02:06 PM
Good information. I have been have the same problem and my city water TDS is about 10 straight from the tap. I periodically flush my ro filter to extend its life but not every time I make up water.

reilly2524
09/22/2017, 04:54 PM
Are you flushing your RO membrane before running it through the DI? If you don't, what happens is that the first minute or so that goes through the DI canister will have high TDS until the RO membrane is flushed out. This has a dramatic impact on the life of the resin. You can avoid it going through the DI canister by using a flush valve for a minute or so... Once you see your RO reading is down to an acceptable level, then you close the flush valve and open up the DI canister and let it run.

Nope I haven't flushed the membrane, (I don't have a flush valve), what I'll do is just disconnect the line, let it run for like a min or two, and then I'll hook it up again. Rookie mistake haha.

outssider
09/22/2017, 05:29 PM
some of us use a "T" fitting with a valve so we can divert the first minute or two of water that would normally go through the resin

45commando
09/22/2017, 09:47 PM
Nope I haven't flushed the membrane, (I don't have a flush valve), what I'll do is just disconnect the line, let it run for like a min or two, and then I'll hook it up again. Rookie mistake haha.


Many hobbyists (myself included) have a RO membrane back flush kit (approx. $15) to flush the RO membrane before ( & also after if you can remember) making RO water. It will extend the life of the membrane & also help keep it working at peak performance.

There is also the issue of "TDS creep", which Ktownhero refered to. Basically the RO membrane takes a few minutes to reach maximum rejection rate at initial start up. An in-line TDS meter (approx. $30) will let you know when the RO membrane has reached it's peak rejection rate (the TDS will drop & hold steady). You can then divert your RO water into the DI chamber.

Lastly, you could have something in your well water, that TDS is not picking up & your DI resin is removing it...that is a good thing


I am on a well also, so to give you an idea of some of the stuff above:
Well water=330-350 depending on season
RO output at start up (TDS Creep number)=125 approx
RO after running=8
DI=0-2 Resin replaced once reading hits 2

HTH