RO/DI question

[scott711]

I have had the same RO/DI unit for several years and have been pretty good about changing the filters and the membrane. It is a basice 4 stage system (1 sediment, 1 carbon, 1 DI, and the membrane). I installed a dual inline TDS meter a while back. I just changed the filters last week and the Membrane is just under a year old. I was looking at the TDS reading and it was measuring in the 100's. I changed the battery, but that didn't do anything. I then had a hand held meter that I used to test it and it measured in the 30's.

 

Do the inline TDS meters go bad?

 

Also, is it worth installing a flush kit? I find it odd that after changing the filters that my TDS could be that high. Especially since my membrane is less than a year old.

 

Any ideas?

[Coral Hind]

Yes, the flush kits are worth it. I like to flush the membrane after changing out the pre-filters as some of the stuff on the filters can clog the membrane. Better to flush those out the waste. If you can remove your in-line flow restrictor from the waste line and just let the water free flow out the waste tube that will flush the membrane. Also, make sure to hold the membrane pressure vessel with the ports up and tap it kind of hard to remove all the air bubbles that might have gotten into the system during a pre-filter change. It is also a good idea to tap out the air bubbles like that at least once a month. If the pressure vessel fills with air it prevents the air locked area from processing water.

[scott711]

Dave, Thanks. I will order one. Should I also get a pressure gauge too? I don't remember seeing an in-line flow restrictor there, but I will check. Do the TDS meters go bad?

 

do the capillary flow restrictors every need to be replaced?

Edited May 14, 2013 by scott711

[Origami]

The capillary restrictor is the flow restrictor. They don't need to be replaced so long as they're clean and clear. It's just a short bit of narrow tubing that restricts flow and produces a pressure drop.

[Coral Hind]

Yes, TDS meters can go bad. Soaking the probes in vinegar can help. They do sell calibration fluid if you want to check it out. I like having a pressure gauge myself but it isn't needed.

[scott711]

could air in the chambers cause a high TDS?

[Coral Hind]

I know the air reduces production but I don't know exactly how it affects TDS. I guess since a reduced area of the membrane is being used it would allow that part being used to foul out faster which could cause TDS to rise.

[Der ABT]

what is your tds going in/straight from the tap.....pressure is good to know, depending on where the feed is if yuo have low pressure it would affect the rejection rate..

 

if you are tapping off something thats way down the line it may be very restrictive....also some houses have a pressure regulator on the feed line or at the street that you could adjust

 

if yuo want to know the static pressure of your neighborhood call the water provider...i know mine in falls church was 45-50...im reading 48-50 on my meter....which is acceptable.

 

also is your DI resin packed tightly to prevent channeling?

[Air Water and Ice]

The air trapped in the chambers is an easy fix. Simply turn your unit to the left while its making water, then to the right while its making water and the air will escape the chambers. But it will not cause your TDS to rise.

 

TDS meters can go bad. That is why its always nice to have a back-up hand-held meter. If you think something might be off with your in-line meter the hand-held one is a good way to find out.

 

The Fast Flush flow restrictors do not typically go bad. The only way they are "bad" is if the handle breaks or if something gets trapped inside them and you are unable to release whatever is clogging it.

[scott711]

I have to check when I get home, but i think the TDS from my tap is lower than from the output. There is obviously something wrong. I am pretty sure my pressure is ok since it is from the same line as the washing machine. I am ordering a gauge to make sure.

 

I just put the resin in the housing. How do you pack it tightly?

 

The dual inline tds meter was bought back in '08 during a group buy here from AWI.

Edited May 14, 2013 by scott711

[Origami]

The TDS from your tap should be lower than the TDS from you waste water, but not from the pure water output. Do you have a handheld TDS meter that you can use as a check?

 

I pack the resin in refillable cartridges using the blunt end of a plastic cup. It seems to work.

[scott711]

i got home and played around with the in line tds meter again. I also tested again with the hand held meter. The handheld registered 2ppm and the inline registered in the hundreds again. Just for kicks I switched the in/out probes and it registered 1-2 ppm. So one of the probes does not work. I will be ordering a new one.

[gmerek2]

I have a different question. I heard the rodi units can go bad after sitting is this true and how long of a sit does it take? If its brand new and dry can it sit for a few months? What about wet? So excited to find a drilled tank now!

[Origami]

Gmerek2, you should start another thread when you have a new question like this.

 

From what I gather, if the membrane is brand new and unused, it can sit for a while. I suspect that it's because there are wetting agents and other preservatives inside the membrane that keep it reasonably fresh. However, when you begin running water through the membrane, these agents and preservatives are flushed and the membrane becomes vulnerable to deterioration and fouling. The same might be true of other stages in the setup.

 

So, yes, if it's new and unused, it can probably sit for months. I've had new RO/DI systems sit unused like this for over 6 months without noticeable problem. If it's used, though, you probably want to get it back in service as soon as possible. I don't know what that timeframe might be but it probably depends upon what conditions the unit is stored in. Maybe a week to a month, but this would just be a guess.

[Origami]

i got home and played around with the in line tds meter again. I also tested again with the hand held meter. The handheld registered 2ppm and the inline registered in the hundreds again. Just for kicks I switched the in/out probes and it registered 1-2 ppm. So one of the probes does not work. I will be ordering a new one.

 

I'm glad that you got this sorted out, Scott. I have an inline TDS meter that's misreading a little bit (not as bad as yours). I've put up with it since I just use my handheld as a backup. However, because of your thread, I think I'll try cleaning the electrodes and seeing if that helps restore function.

[scott711]

I'm glad that you got this sorted out, Scott. I have an inline TDS meter that's misreading a little bit (not as bad as yours). I've put up with it since I just use my handheld as a backup. However, because of your thread, I think I'll try cleaning the electrodes and seeing if that helps restore function.

 

how are you going to clean the electrodes? Is there a way to recalibrate them?

[Origami]

Someone posted something about using vinegar. In all honesty, I'll probably use a vinegar soak, followed by an alkaline soak, both with a mechanical scrubbing and a good rinse. The objective is to clean off the electrodes of any deposits or biofilm which may impact measuring conductivity. After all, that's all the TDS meter is really doing - measuring conductivity across a calibrated distance / area. If dirty electrodes are the problem, then this should improve performance. If it's something in the wire or input circuitry, then I'll be buying another dual TDS meter. In general, though, my TDS meter seems to be behaving normally. That is, I see the higher burst of TDS out of the membrane upon startup which then falls off towards zero rather quickly.

[gmerek2]

on amazon they sell calibration fluid with TDS of 342 PPM. if yours reads 350 with the controll of 342, then just subtract 8 during a normal reading if you cannot calibrate the machine.