I just got an RO/DI system from bulk reef supply (about a week ago) and about 1/5 of the DI resin is already brown.  The TDS in hovers between 500-700, the RO out is about 30, and the DI out is 0.  How long does DI resin usually last in the Cedar Rapids/Iowa City area?  How often do you flush your RO membrane?  How often do you replace you sediment filters and carbon filters?  How often do you replace the RO membrane?  The way it's looking, I'll be replacing the DI every month!  The sediment and chloramine/carbon filters look like they should last about 6 months while I've read that the RO membrane should be replaced every year.  I'm just trying to get a handle on what's going on here.  I've heard of people going 4 months without replacing their DI resin.  I lose about 20 gallons of evap per week and do monthly 20% water changes. So that's about 1200 gallons a year.

TDS of 500-700?? Wow!! Thats pretty high. Our here near Waterloo is around 320 or so. Depending on which membrane you have will determine how long your DI resin will last. For instance, i was burning through DI resin with m 100 gpd membrane because it had i lower rejection rate therefore letting more TDS get to my DI. I was replacing resin every couple weeks. Since then i have switched to a 75 gpd membrane with a higher rejection rate, now my DI resin last for months and months.

I have the 75gpd. I think it's rated at 98% rejection. I really think it was a flush issue. I checked the TDS this morning and off the RO membrane it was around 80!! I did a 1 minute flush today and it went down to 15. Maybe I just need to flush it everyday... Good thing DI resin is pretty cheap.

Hello guys. I am having the same problem. I just purchased a OceanWave 75GPD 5 stage RO/Di from The filter guys. Its a great unit but I found the same issue. After 1 month of use my resin is allready brown. I have only made approximately 50 gallons of water so far. Seems pretty quick. Correct me if I am wrong but I was told that the only way you can correctly determine that your DI resin is shot is to measure TDS coming out of DI.  If it reads zero or a little above you will be fine. So i just bought a TDS meter today and hope I can get a little more use out of my resin. Even though it is not that much it it still adds up if I have to change it every month. GOOD LUCK

I think if it's completely brown you should replace it. I guess I didn't realize how hard the water was here! I came home today and the TDS off the membrane was 110. Did a 5 minute flush and it's back down to 20. Maybe I should just store my make-up water in a giant bucket like I used to. Right now I have it running continuously through my level-loc.

I have the same problem! i bought a new membrane because I thought that was the culprit, but it only made it worse. I think a big factor is having enough pressure...my next attempt will be to buy a booster pump.

Posted By foxface on 12/02/2008 02:58 PM 
So i just bought a TDS meter today and hope I can get a little more use out of my resin. Even though it is not that much it it still adds up if I have to change it every month. GOOD LUCK

May I ask where you bought the TDS meter at?How much do they run?

Pressure is not an issue for me. The gauge is at 60 PSI when water isn't flowing, 50 when it is. I think this area just has extremely shitty water so the RO membrane gets cashed quickly and has to be flushed regularly (like every 5 gallons...)

TDS meters are pretty cheap. Less than $30 at most places. The dual in line from bulkreefsupply is like $24 and the single is $20 or something like that.

Came home today and it was at 130 off of the RO and 1/4 of the resin is brown now. I flushed it again and have made 5 gallons of water with the TDS off of the RO at 12... I really think running it continuously throughout the day off of my level-loc clogs the membrane. I'm definitely going back to the bucket method.

Went back to the bucket method. Checked the TDS this morning just to be sure that solids weren't leaching through the membrane when there wasn't any flow and it's steady at 14 TDS off of the RO. Lesson learned. Don't run your water purification system all day long