RODI Question

[coker98]

Hey Everyone!!

I feel like kind of a noob for asking this as I have been reefing for a while now but Ive come across an issue lately that I cant wrap my mind around.

I have an RODI unit that has been in service for the last 8 years. I switch the carbon and sediment at least quarterly. The DI is seemingly needing to be replaced more often. I usually replace the RO membrane yearly.

When ever I replace the DI resin, I start at 0 TDS. after making about 120 gallons of clean water I start getting a reading of increase in TDS.

I dont know whats wrong.

Can the unit itself get old and degrade to speed up exhaustion of media?

Does making 120 gallons of clean water per refill of DI resin sound correct?

How long should the filter media be lasting? DI resin? Carbon? Sediment? Membrane?

The brand of filter is from aquariumwaterfilters.com

Thanks for any help.

 

[James77]

What brand membrane and what rating is the membrane? Can you measure the TDS out of the membrane before it goes into the DI?

If you have high TDS source water, and a low rejection membrane, you can waste through DI. I use a 75 gpd membrane, and I have very low tap water TDS(about 65) so the output on the membrane is usually 0 or 1, so my DI lasts for a really long time. I just changed it today for the first time is a year, only because it was a year.

 

[coker98]

I cant remember the brand. Possibly a DOW brand.

100 gpd.

I can check the TDS out of the membrane tonight and the source as well.

Also, my system psi is at 44ISHpsi.

Is this okay for an operating pressure?

 

[ddropski]

sounds like the membrain is going wacky ... ther resin is burning out cuz the membrain isint catching everything

 

[coker98]

sounds like the membrain is going wacky ... ther resin is burning out cuz the membrain isint catching everything

Could definitely be the issue.

I just did a reading on the incoming water.....401 for tds.

Before the resin....172

Does this give anymore insight?

Thanks so far also.

 

[coker98]

I'm also not using the output water for my reef tank.

My quarantine tank is another issue.

 

[shifty51008]

That membrane is no good, with 400 tap water you should be getting less than 10 at worse going into the di. I suggest getting a dow 75 gpd membrane from brs, Buckeyefield supply, spectapure, ect and also getting a flow restrictor to match the 75gpd membrane. Also it may be a good idea to purchase a booster pump, you want around 60-90 psi.

 

[Bpb]

Yeah I've had my 4 stage running for 1.5 years. Replaced sediment and carbon block twice. Same membrane and DI resin. Still get 0 tds product water with 350 ppm tap going into the unit. I make about 20 gallons a week. I'd say something is wrong if you're burning through resin and membranes that fast

 

[Allentown]

Does size matter? My tap water I'd only 54ppm and I burned through my DI and destroyed my RO inside 9 months with a mighty mike portable.

I have read somewhere that chlorine/chemicals can be higher in some cities and they destroy your RO membrane quickly which in turn blows out your DI resin.

The solution seems to be stock piling a bunch of carbon/pre-sediment prefilters and changing them more frequently to protect the RO membrane.

A tds meter I'd useless in figuring this part out. Im going through this process myself. Going to try and change pre-filters at 6 months and see if that saves my RO. If not I may have to try it at 3-4 month intervals.

 

[coker98]

So I should be changing my carbon and sediment more often to preserve my membrane?

 

[Allentown]

Most likely yes.

 

[ggsteve]

Boy, this is beginning to sound a lot more like an art than a science. I talked to one of the owners at BRS and he told me the worst water he had ever seen was the well water at his Mom's house. It ate up a full charge of DI resin filling a 150 gal tank he put in for her. I think he said it was due to high CO2 in the well water. Unfortunately, my crappy well water is about as bad. I've made about 150 gallons now and my DI has pretty much all changed color and the TDS after the resin is creeping up to the high single digits.

 

[Allentown]

Boy, this is beginning to sound a lot more like an art than a science. I talked to one of the owners at BRS and he told me the worst water he had ever seen was the well water at his Mom's house. It ate up a full charge of DI resin filling a 150 gal tank he put in for her. I think he said it was due to high CO2 in the well water. Unfortunately, my crappy well water is about as bad. I've made about 150 gallons now and my DI has pretty much all changed color and the TDS after the resin is creeping up to the high single digits.

You also could have had a bad RO membrane if you ate through a resin that fast.

 

[fltekdiver]

Yeah I've had my 4 stage running for 1.5 years. Replaced sediment and carbon block twice. Same membrane and DI resin. Still get 0 tds product water with 350 ppm tap going into the unit. I make about 20 gallons a week. I'd say something is wrong if you're burning through resin and membranes that fast

I have the same reading, 350 ppm in, and 0 out, made over 500+ gallons so far, haven't change anything yet

MY PSI is also @ 45 PSI

 

[ggsteve]

You also could have had a bad RO membrane if you ate through a resin that fast.

TDS is about 300 ppm out of the tap and before the DI chamber is about 7-15 ppm depending on how long it's been running.

 

[Allentown]

Its a mystery. My tap water is 54ppm and yet it still ruined the RO membrane when i didnt change my prefilters....