Help with RO+DI unit

H

HELIREEFER

i Just got a new ro di unit and hooked it up to the washing machine cold water pipe and i'm using the washing machine drain

It is an aqua safe unit - TFC membrane and purolite color changing DI

How long does it normally take to get the tds reading down to less than 10

i flushed the membrane and prefilters for 10 min each per instructions and i still can't get anything lower than 72
i have only probably run 5-10 gallons thru at this point though

tap water is tds 222
 
hmm....
I would run it a little more. I know i flush my di's for about 3-5 b4 i start using it. I would shut off he di and run the RO for a little. Check your water from here. Also, I got fooled once on my reading once or twice due to contamination in the cup i was using. Just a fyi.
 
This is a *real* longshot, but based on the info you've seen, something is really not functioning properly. The DI resin *alone* should be pulling it close to 0 TDS even if the membrane was bad,etc *if* it is given enough contact time with the water. I'm wondering if the RO membrane is not seated properly and is leaking input TDS water to the output side instead of forcing it through the membrane and also producing more water flow that is too fast to allow the DI to soak it up. Do you have any idea what the rate of water production is at the moment? Really guessing at this, but you should be getting 0 TDS water after the DI resin get flushed good. I have our units hooked up to the washing machine water/drain just as yours is and get 0 TDS water almost instantly after a cartridge,DI change. HTH

Doug
 
Normally membranes have a food-grade preservative in them. You'll need to run it long enough to toss out 3 to 5 gallons of pure water (basically one hour's worth). If possible, I would run it so that you collect RO water only and not waste your DI (if your unit allows you to divert the water before the DI).

If you can't solve this, contact the vendor as they are very helpful. Be sure to post their feedback so others can benefit from this thread.
 
ok i tested the water after the membrane and it reads 91
after the di reads 70-72

i thought of something, i don't kno wif it means anything
- when i opened the unit and out it together, i opened the mebrane plastic bag but the bag wasn't sealed, like the edges where melted to form a seam, but it broke. So could my membrane be bad?

:shock:
 
oh, hey marc.


I know you sell your own units, but can u sell just a vertical DI canister and cartridge, and if so, how much?

i don't see it on the website
 
Your membrane could be bad if it totally dried out...

Another thing that got me, make sure the membrane is FULLY seated in it's housing... I mean you've really gotta ram it in there... I had a problem once where the membrane wasn't ALL the way into it's housing, and I was getting horribly TDS out of it, as the water was taking the path of least resistance, which was to go right around the membrane...
 
@Serk wrote:
Your membrane could be bad if it totally dried out... Another thing that got me said:
I thought I remembered that happening to someone and is part of the reason I suggested it as about the only thing I could think of too. If not, the membrane must be bad as the before/after TDS would mean it's rejection ratio is *horrible*. I'd agree with the possibility of bad too, but just be sure it's fitted correctly first.

Doug
Click to expand...
 
OK i emailed the vender and they emailed me back with a list of questions
source tds, tds after mebrane etc...

What was interesting is he asked what is the tds of waste water, when i tested it i was surprised 296-300

they replied quickly though
 
Those are some odd numbers.

Tap 222
After membrane 91
After DI 72
Waste 296

How is the TDS of the waste water higher than the tap water in the first place?

Btw, if your RO/DI has an additional filter after the DI for "taste", remove it because it will add TDS to the water.

If the membrane you have has a 90% rejection rate, the water coming out of the RO membrane should be 22. If the membrane has a 98% rejection rate, the water coming out of the RO membrane should be 4.

The lower that number coming out of the RO, the longer the DI media will last because it won't be depleted as quickly when the water is so pure.
 
@Marc wrote:
How is the TDS of the waste water higher than the tap water in the first place? said:
I've never tested the TDS of my waste water, but that actually makes sense to me, as the TDS will be concentrated into the waste water...

For example, we'll say you've got 100 TDS source water, and it takes 5 gallons of waste to make one gallon of pure. If your product water came out at 0 TDS (I know, not accurate, but trying to keep it simple) then the concentration of TDS in your waste water would go up, as you'd have that same 100 TDS, but it would now be concentrated into 4 gallons instead of 5...

(Just like how your salinity goes up as your tank water evaporates)

But I do agree, something wonky's going on...
Click to expand...
 
the membrane is in as far as i can get it, i have checked it twice. I really think my membrane is bad now. Waiting on the vendor to repsond

Thanks everyone for your input, I'll let you know how it turns out
 
Ok the vender had me measure the filtered water and waste water produced in one hour which was
5 gallons out the filtered end and 7 gallons out the waste water end. Which i thought was wrong

i emailed them the numbers and they are sending me a replacment ro housing. I guess they are thinking that the waste water is mixing with the filtered water and the mix is then going out to the DI? Due to this i guess the membrane is not being penetrated as well either

we'll see.... :roll:
 
After thinking about it for a while i hear a faint buzzing when the unit is running at the end of the ro membrane housing, it sounds like something going past an o ring. I didn't even register it before.

so maybe this will fix it! :?:
 
Glad to hear they are trying to help. The symptoms sure fit what we were describing above (input leaking through to output line without going through the membrane), but I for one would not have suspected the housing itself. It will be very interesting to hear what finally fixes it, as it will be *yet another* thing to check when it happens to someone else. The problem with the membrane or the RO housing being defective is that it will be so very difficult to diagnose....as you are seeing. Since you've heard some possible leaking, it would sure make sense and I hope that solves the problem. Thanks for the continued posting as it may help someone else someday.
Doug
 
While waiting for the replacement, if you wanna try something, put a thin layer of vaseline around the o-ring on the membrane and re-seat it...

(Or just wait for the replacement... :) )
 
I was thinking about trying something like that serk.

I think i will when i get home and post results.

But i tell you what, i removed the membrane housing and turned it vertically on the floor and pressed that membrane in as hard as i could into that thing, it won't go in any further.
 
Ok, i got the replacment RO membrane housing today, i installed it and turned the unit on. The TDS dropped from 72 to 9

Soooooo. I still have a small TDS reading, is this low enough to use?
The unit has been sitting a while so I am running it now and will test again in an hour or so to see if the tds drops to zero
 
OK i tested again TDS after mebrane 8 after di 7

It looks like my DI is not working. I wonder if the waste water mixing with pure water getting into DI damaged it??
 
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