ro/di problem(again!)

[scott]

ok, i have been using the same unit for all my tanks for about 1year. the tap water is as follows ph 10+ , tds 190uS. after the ro/di filters it the ph is 5.5 and tds 2uS. i just replaced the di resin cartridge and now the filtered water still has a ph of over 10. i am using the same brand di catridge as always (kent). i tried a second cartridge that i had with the same results. when i put the old cartridge that i removed in the first place because it was almost exausted back into the unit the ph dropped back to 5.5 so i am assuming the problem is with the new cartridges. i even tried running the new cartridge overnight, discarding the water, and still ph over 10. i don't understand why these 2 new cartridges do'nt lower the ph. has anyone ever encountered this problem and if so what was the cause and how was it fixed. i am boiling some peat as a write this to lower the ph of the water i have in the barrels currently but i would much rather the di worked properly and lowered the ph as it always has in the past. this is not the 1st time i've replaced the cartridge, i've used dozens of kents di "ion exchange resin cartridges" without having this problem. help!?!?

 

[tjudy]

What is the uS reading with the new cartidge? RO/DI should take the water close to neutral. The 5.5 pH is low IMO, bu tthe 10 pH is definitely weird.

Remember that carbonate hardness will affect the pH, and the RO does remove all the carbonates. Carbonate hardness does nto register as uS either, so the KH value cold be high while conductivity is still low. A DI should help to reduce alkaline ions though. I am not familiar with Kent resins. I buy my resins in bulk from Spectrapure and fill my own cartiridges. There are many types of resins, and different mixes do better in different water conditions. You might consider dropping the guys at www.spectrapure.com a note and ask what mix they suggest for your water conditions.

 

[scott]

thanks for the info ted. with the new cartridge the uS is still 2. i will definitely check into the link you posted. i would rather do it that way if possible. the reason the ph from the tap is so high is because of something the use to protect the old pipes, at kleast that's what the water authority man told me. i will check the kh but like i said the old cartridge works fine. maybe kent changed there mix or something.

 

[farm41]

tds 190uS.

Scott,

Just to make sure, we need to clarify TDS or EC. TDS is measured in ppm and EC is measured in µS.

Which measure are you using?

 

[scott]

i'm sorry i am using a tds meter so the ppm reading is 85.

 

[tjudy]

TDS and EC are the sam thing as far as a meter is concerned. Meters measuer electric conductivity and use a conversion factor to report in ppm. You mentioned that you were getting a ppm of 85, and a uS of 2? That is really off the standard conversion factor 1 ppm = 2 uS. Have you calibrated the meter recently?

 

[tjudy]

Oops.. I misread the posts. The numbers were for the tap water right? 190 uS and 85 ppm. That computes.