RO quit!

A

AndyKatz

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Apr 24, 2008
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Greetings everyone,

I've been reading this forum for a spell, but I haven't posted until now.

We have a 55 fowlr established about 14 months ago. It's stocked with two triggers, two puffers, two striped damsels and one blue damsel. It's been a healthy tank, only one casualty and that was due to a disagreement over who was in charge last year.

We used tap water (NYC) and did ~ 10% weekly changes.

Needless to say with two puffers eating like pigs nitrates and phosphates climbed in spite of the changes. So I finally decided to go r/o, buying the Pet Solutions dual filter. We set it up and got about 20 - 40 pounds of pressure, resulting in maybe 20 gpd. Not great, but adequate.

After about 8 weeks, producing less than 100 gallons total, it just ground to a halt. I was getting maybe 1 gpd for a day or two. Now, nothing. Waste water still drains, but no filtered water. I've checked all the connections, they're intact. There's no kinked tubes, or blockage that I can detect. The pressure in our taps appears not to have changed significantly.

I checked the pre-filters. They've obviously been used, but not to the point of utter blockage. I rinsed them out. No change.

I'd be willing to invest in a water pump if that's necessary, but first I'd like to find out if others have had similar problems with their r/o filters.

Thanks,

Andy
 
No never had that happen...

The most likely thing is the membrane has clogged shut. :(


You always need 3 or 4x more rejection water than product water. If this is not the case then precipitates form and promptly clog the membrane.

Also if you let the membrane dry out it's toast.

Also the bare minimum is a sediment filter which is then followed by the carbon BLOCK filter. The sediment filter yanks out all the iron and rubber and metal shavings that come down the pike. The carbon block filter rips out the fluoride and chlorine because if any of that hits the membrane .... You guessed it - it's toast!

Now something not realized by most is that on initial setup the carbon block filter can put out a cloud of black mud - membrane clogging - black mud.

Whenever you put a new set of filters into service you need to disconnect the line to the membrane and run it into a pail of the sink for many minutes until the black dust is gone. Perhaps this has clogged your membrane?

Further you should regularly test your carbon filter's output for chlorine as that means it has done all it can and needs to be replaced.

The smart individual always puts a TEE in the carbon block filter outlet line and two valves. One that blocks flow to the membrane and one that is an outlet that you can flush thru and test via.

Now to troubleshoot yours.
Does the same amount of rejection water seem to be present as originally?
Pull the carbon block outlet line and see if you get plenty of flow.

Pull the membrane and look at it.
 
Hi,

Thanks for the info.

I did flush the system per instructions prior to initially inserting the membrane. And I believe at its peak efficiency the unit *was* putting out 3-4x more waste water than filtered.

By now the membrane probably has dried out because I did take it out to inspect it (I seem to recall having read that they oughtn't be allowed to dry out, but I'd forgotten till you mentioned it). But that wasn't the cause. The filter seemed to fail in mid-bucket. I set it up in the shower, and after about an hour I came back to find it only one third full, when it ought to have been nearly full. It hasn't been right since then.

I'd be happy to replace to the membrane if I could be sure that's the cause. Otherwise I don't have too much money to spend on this right now.

I can remove the carbon filter and try it--the unit does have a "T" valve set in the feedline to the membrane. I'm not sure how to use this to test the system, but I'll take another look.

Question: if the carbon filter's primary role is to remove chlorine, is it really necessary, or can one leave it out and use a de-chlorinator on the filtered water?

One reason I ask is that in addition to cost, any replacement filter will have to come from an mofs, and that will take time. Meanwhile I've been using Poland Spring to keep the tank topped off (we have two fans running to keep the water cool). You'd think one could buy distilled water easily in NYC, but it doesn't seem to be the case.

I don't know ... as I wrote the tank's been established for over a year on tap water alone. Maybe I shouldn't have tried to fix something that wasn't broken in the first place.

But I will test it out sans carbon filter and see what happens. I did notice that when the I had the membrane chamber disassembled and the water running, the inflow to it was very, very slow. It's hard to see it building up enough pressure within to permit adequate filtration.

Thanks again.

I'll post my results tomorrow.

Andy
 
Unless you can somehow dechlorinate before it reaches the membrane, then it won't work. The point is to keep chlorine from destroying the membrane, not necessarily chlorine free product water. I would suspect sediment blockage before a carbon filter problem. Test it sans prefilter, then see what happens. Do you know the micron sizes on your prefilter and carbon filter(s), by chance?
 
Thanks for the comments. I feel, duh!, I ought to have realized that the carbon pre-filter was intended to protect the membrane:(

I already tried it without the carbon pre-filter. Pressure and output were back to normal. So I'll have to replace the carbon.

One question, how does one gauge the continued efficacy of the membrane? Does it cease passing water, or does the tds level simply rise?

Andy
 
The latter. That is why it is handy to get the dual in-line TDS meter to figure out what portion is going bad--the membrane or the DI resin.
 
If you let it go too long the membrane just starts coming apart.

My system was holding staedy at 11ppm TDS for about 2 years which was fine for my FOWLR. Then one day I pulled a glass of water and it was filled with floaters yeeck.

I replaced that 7 year old membrane with a new one. Now I have less than 1ppm.
 
That's true, but most replace it after it drifts above a few ppm TDS. I don't think there are many people that wait that long. Personally, I replace it once it begins giving me anything above 0.
 
Thanks for the comments & info. I felt I couldn't go without top-offs while waiting for a replacement carbon filter from the mofs, so I bought high quality carbon at the lfs, rinsed it thoroughly and packed it into the chamber using a generic media bag. Pressure and output are back to normal, and this ought to keep chorines at bay while I await a proper replacement.

Another question, are replacement membranes geared to fit particular brands, or is there a standard?

Thanks again,

Andy
 
Membranes are standard size. Just be sure to get the one that matches your output rate. I am still a bit worried that chlorine may get past that carbon and get to your membrane. Packing a media bag vs. flowing through the cartridge are different--water can flow around the media bag much more freely. Did your LFS not have replacement carbon cartridges?
 
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