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View Full Version : Calgary water and RO; what's your TDS after the RO?


Delphinus
10-24-2005, 05:18 PM
If you have an RO unit, and you measure your TDS, what typically is your TDS reading after RO membrane (but before the DI stage)?

I know incoming TDS is usually around 400 or so for me. But I was expecting my RO readings to be more in the 5-15 range after my RO, but I usually get readings more like 60-80.

I've replaced my membrane (and all the prefilters of course), but I still get readings like that. After the DI the readings are 0 so I think the TDS meter is OK.

Maybe something in my configuration is causing membranes to fail prematurely? Or can a RO unit be functioning properly and still yield water with a TDS in the 60 to 80 range?

EmilyB
10-24-2005, 10:05 PM
Mine is 0-5 Tony. Something sounds haywire there. Mind you my tap water is around 175ppm. Rejection rate should be 95-99% so you are still way high. The DI won't last long at that rate.

Delphinus
10-24-2005, 10:09 PM
You got that right. 3 weeks on and almost 1/3 done.

Thanks for the info.

I'm pretty sure something's wrong. The fact that I'm on my 3rd membrane in a year that exhibits this means I must have something wrong in my configuration. The only thing I can think of, off the bat, is the fact my RO/DI feeds a number of float valves (1 for each tank). So the pressure in the discharge line is always high (thus shutting off via the solenoid shut off kit). So it's always on for a short burst followed by a long period of off, following the evaporation rate.

The only thing I can think of to change that is to fill a bucket first, then shut off the inlet water. Let the bucket feed the float valves over the course of a day, then refill the bucket in one go (once a day kind of thing).

How do you have your top off? Float switches or float valves?

EmilyB
10-24-2005, 10:38 PM
How do you have your top off? Float switches or float valves?

Mine's not connected to the RO unit at all. Still mostly Barry Bucket around here.... :redface: :lol:

monza
10-24-2005, 11:29 PM
Tony

After my RO a reading of 2. I had a bad membrane and had similar results to what you have going on. Luckily I changed it and things have been running smooth. So you must have something wrong for sure. So you'll have to fix that and I don't think it is related to your float valve set up. I believe it is best for your RO to operate a few times every day, the more the better for it. Is that not what you have happening? I believe the worst thing for RO/DI is long periods of no flow like a day or two.

For info sake I have my RO/DI plumbed into a 5 Gal. pale on a float. In the pale are my two top off pumps. One pump is controlled by a Tsunami see link, it supplies my predator tank.
http://www.mops.ca/cgi-bin/SoftCart.exe/products/DOCH-AT1.shtml?E+scstore

It works fine and after three years has not failed (knocking on wood now). It did not have the exact control I was looking for on my reef and went the Tunze top off system on my reef. I love that little toy, pricey yes but does a great job. I'd guess it turns on dozens of times over a 24 hour period keeping the flow through RO/DI going on and off.

Also plumbed out of the 5gal I have a line that flows down to a 33gal rubbermaid to store water change water. There is regular float in that container. And then... from that container I pump manually into other rubermaids to mix salt in.
The end sorry that was so long.

Dave

Delphinus
10-24-2005, 11:37 PM
Aiiee, now I don't know what to think. I thought maybe the constant on/off/on/off/on/off of my setup what was may be killing the membranes.

Anyone consider themselves an RO savant that could come over and help me trouble shoot my setup? The thing is I've been having my RO setup this way for years and only this last year have seemingly had a problem with things.

My water pressure is way lower in my new house than it was at the old house. The first thing I did was T into my water supply before my pressure regulator (I don't know why my house has a pressure regulator so I don't really want to remove, defeat or even adjust its settings too much). Before the regulator the pressure is about 76psi so I assume that's enough to comfortably run the RO.

I'm not sure what else I should be looking at.

Bob I
10-24-2005, 11:43 PM
Ahhh the joys of no RO. :biggrin:

monza
10-25-2005, 12:09 AM
Is it a new RO/DI or did it work fine at the old house? Assuming it's a older unit...kind of an obvious question but did you change anything on the unit when you moved?

Delphinus
10-25-2005, 02:39 AM
It's a new-to-me unit. Basically the shell and then the innards are all I completely new (membrane, prefilters and some of the fittings).

The one before, as far as I know, it worked fine at the old house. Course I didn't always have a TDS meter though, so my perceptions may be off a bit.

Nothing was changed in the old unit in the move; and it seems to me it was after a year that I really started noticing things going aksew.

Bob, I remember when you told me that only fools use halides over their tanks, and that you would never ever use those. :razz: Thanks for the helpful post though :lol: At least you get one more post count now.

Bob I
10-25-2005, 02:50 AM
Yes, but you got four to my one. :mad:

monza
10-25-2005, 05:35 AM
I don't know, if I was more of a RO savant sort of person I'd help but I'm not. Is it a brand name filter set up? Maybe post a pick of the set up and some might notice a flaw in the configuration. If that doesn't work sell it to some one from Edmonton, get a new one and be done with it!

One other thing, you say "Nothing was changed in the old unit in the move; and it seems to me it was after a year that I really started noticing things going aksew. " Is that because you got a TDS meter? Could the thing be screwy from the get go?

For what it's worth I have one of these units and it's great because it supplies quality drinking water as well. The difference in taste is amazing.
http://airwaterice.com/product/1DUALHR

Dave

EmilyB
10-25-2005, 06:11 AM
Bob Bob Bob...I thought you believed in constructive posts. :razz: We folk who don't take our tanks down every couple months have to have other options you know... :lol:

Tony, I did get a bad membrane from AquaSafe, proved it by substituting with someone elses. You might try that.

monza
10-25-2005, 06:15 AM
One bad membrane sure but three? Something is wrong.

Dave

Delphinus
10-25-2005, 02:45 PM
I've switched the configuration for now to only fill my water barrell and just feed the float valves off that; will see if this makes a difference. It usually takes about overnight to fill that thing and it holds, I think, 40g, so a fill should last me about a week.

If I flush the membrane then the TDS on the output falls down to 15 which to me seems a more acceptable level (although I still wish it were a little better, but hey it's better than 60).

As far as configuration goes I'm not really sure how you can screw up with these things? Water goes in, water comes out in two places, and one of those streams is more better than the other. :lol: You need a flow restrictor that matches your membrane capacity and you put that on the waste line (otherwise a flush kit doesn't do anything). Am I overlooking anything here? And then I guess the only thing is if you want to get real tricky you can put a flush bypass valve on your waste line, and the solenoid shutoff which feeds off the output line and impacts back to the input line.

I guess when I say "three membranes" I should qualify that the first was, of course, several years old so maybe it doesn't count. So really I'm looking at being on my second replacement membrane and I'm wondering what's up. I would have upgraded the membrane anyhow though since the old one was 35gpd and I wanted to go to 100gpd (although it's not 100gpd at the pressure it's run on). I am using, as far as I know, the appropriate sized flow restrictor.

Anyhow thanks for the thoughts ... will have to scratch the noggin a bit more on this but for now I'll see if the reservoir changeout has an effect.

BMW Rider
10-25-2005, 02:51 PM
Is it possible that the membrane housing is the problem. Perhaps the membrane is not fitting properly and is allowing some unfiltered water to leakpast and mix with the RO water.

monza
10-25-2005, 03:49 PM
From what I’ve read and been told the less you use a RO/DI the less efficient the unit becomes. Unless you have an automatic back flow that cycles every so often and then it does not matter.

Good luck with it, post your results. I can tell Bob he’s lurking because he wants a RO/DI!

Dave

danny zubot
10-27-2005, 02:27 PM
Yes, us fools with our RO units are just staying mainstream Bob. The fact is though, Calgary water not only has higher PO4 and chlorine, but the heavy metals are what will inhibit your tanks' success over time.

OCDP
10-29-2005, 11:11 PM
In all honesty though, our tap water is not that bad. Not nearly as bad as others. I should invest in an RO/DI , and I know I should have one by now. Just can't find the funds to order a brand new one online. A used one on the other hand.... I would be fine with that.

Delphinus
11-07-2005, 06:21 PM
So my 55g drum or however big it is finally emptied over the weekend. Gave it a rinse and turned on the RO/DI to refill. I first flushed the membrane, after about 30 seconds the TDS in the post-RO (pre-DI) step came down from about 80 tds to about 15 tds. For the remainder of the fill the tds on this step hovered around 13-15. That seems not so bad, although it's not the 2 or 0-5 that Monza and Emilyb report. (Anyone else measure the TDS between the RO membrane but before the DI? What are the numbers you get?) Post-DI the tds is a solid zero but the resin is now almost halfway consumed.

So I think what's happened in my case is the constant cycling of the unit due to the top off for multiple tanks led to premature failure of the membrane. 15 tds isn't too bad but I think I'll budget for replacing the membrane again and take it as a lesson learned.

There is an interesting idea for combating "TDS creep" in the latest reefkeeping.com featured aquarium where the guy has his float valve inside a chamber inside the reservor that doesn't kick off the float valve until the reservoir is completely empty, thus allowing the RO to kick on only to fill the reservoir from empty (instead of the constant on-off to match the evaporation rate). http://www.reefkeeping.com/issues/2005-11/totm/index.php

Although given how long my drum lasted before refilling I think I can live with manually turning on and off my RO from now on.

Canadian Man
11-09-2005, 07:55 PM
Hey Tony.

For what it's worth, I used to get reading no higher than 0 to 4 after my membrane.

My Di cartridges were lasting about 8 month's to 1 year.