Tds of ro/water up/down??

The tds of my ro/water is very irratic, one minute it shows 002 the next time i use it its 039??
It has new filters and membraine and gets run every other day!
do i have to flush water through it for a few minutes before i test it?

Also how long does it keep?
I filled a drinks bottle on monday and i checked the tds of it today and it was way up on its original reading!!

any help would be greatly appreciated.

 

TDS reading shouldn't really fluctuate too much with clean RO and if you've just changed the filter membrane and flushed etc. I would check your TDS meter is clean, and give it a light scrub with a clean unused toothbrush and see if that makes any difference.

 

Your tds will fluctuate some, depends on water pressure in, and water temp going in can change it some.

 

The TDS reading is probably from bacteria already on the bottle surface.
RO water will keep in a clean bottle the best way to clean the bottle is by boiling some tap water and then sterilise the bottle with it for 10 mins then pour the boiling water away and then rinse with RO water 2-3 times to remove any residue from the tap water.

 

Or try covering and storing the RO water in the dark if your not already doing this.

 

I think invert phil is on to something. I know airwaterice does a free TDS reading for you. Their instructions read something like this: use a plastic bottle, fill and rinse 3 times with water to be tested. Cap up and send it to us.

With that in mind, here's what I would do if I were you: I'd fill a small glass test-tube (like the API test vials) with your RO/DI water, cap it and shake. Dump it out and repeat this 3 times. Then test the water in the glass vial.

I have a sneaky suspicion your fluctuations are attributable to the vessel in which you're testing rather than your RO/DI unit.

Let us know!

 

Its possible your TDS meter is faulty as well. Is there any way to doublecheck against another meter?

As far as storing RODI water it should keep indefinitely as long as its stored sealed up and no organics or anything get into it. Pure water doesn't spoil so it's a matter of how careful you are with what gets in it and the container its in. AFAIK anyway.

 

Just run it for a few minutes before you test. The first few minutes the TDS levels will be higher. After that it should be extremely low.