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Old 08-04-2010, 01:15 AM   #1
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RO/DI at 7ppm

Hello, I have been out of the saltwater aquarium world for about four years now and just decided to get back into it when I bought a 29gallon Biocube off eBay inc. live rock and sand Anyways...

I have an RO system that has been sitting in my basement for like two years. Decided to get it back into action. I changed the filters and hooked it back up and let about 10gallons of water run through it. My meter is not reading 7ppm right now, and I was wondering if this would be OK to fill my tank with. My normal tap runs about 130ppm and when I had my last tank I made the mistake of putting that in my system! Do you guys think 7ppm will promote bad algea growth? I am unsure of why its still has a reading after I replaced the filters, but 7ppm doesn't seem like a big deal. Let me know thanks!
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Old 08-04-2010, 02:05 AM   #2
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Welcome to AA!

Did you replace the filters and the RO membrane? If the membrane sat that long dry it's definately shot, so if you didn't change that out too then I'd go ahead and do that. Same obviously for the DI resin.

If you did replace that too, let it run for a bit. When I first got my RODI unit I let it run for a few hours before I ever used the water. Mine didn't show 0 at first either, but after a bit of being wet it came down to 0.
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Old 08-04-2010, 02:49 AM   #3
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Well I replaced the bottom 3 cartrages and the RO one. It is a five stage filter I believe, so I might be missing one. I don't see anything else that unscrews though! Any suggestions? Also will the 7ppm make a huge difference? Just don't want a cyno outbreak like I had back in the day.
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Old 08-04-2010, 09:57 AM   #4
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If it's a 5 stage then it should be a RODI not just a RO filter. RO membranes have rejection rates of 90% - 98%, so your tap water at 130 would be at 13 - 3. Being at 7 means you are getting about 95%.
The DI cartridge is what will take that down to ZERO.
It seems to me that the filter is working fine, but either you don't have a DI cartridge, the DI resin needs to be replaced, or you need to run it for another hour or two till it gets down.

But to answer your original question. A tds of 7 is fine for filling a tank, and is Soooo much better than 130 tds from the tap.
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Old 08-04-2010, 12:13 PM   #5
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After I let the water run for awhile it is now down to 3ppm. I fogure I should be all set with that but as above mentioned ill look into the DI portion of my system
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Old 08-04-2010, 02:23 PM   #6
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yeah, i would think that the resin is shot, because if it were only thte RO filter the resin would still get it down but would be used up very very quickly.

3 would be good enough for me. but i am loosy goosey about things. I dont even have the DI section and have been running with 12ppm.
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Old 08-04-2010, 04:04 PM   #7
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This actually is a very useful thread. How high can we get away with for a TDS? My TDS is now at 1ppm. Ive had my system for over a year now, but only use it for a 20g tank. My first thoughts would be to order all new filters (minus the RO membrane). It would be great to be able to save some money and wait for the TDS to raise to some level where you guys agree it to then be worth the money for new filters.

The thing that worries me is, what substance is causing the 1ppm?
Could be something more irritating than nitrates. Maybe chlorine? Maybe phosphates? Maybe silicates? Maybe something terrible like copper? Maybe a combo of all those things?

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Old 08-10-2010, 11:04 PM   #8
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Quote:
Originally Posted by mrg02d View Post
The thing that worries me is, what substance is causing the 1ppm? Could be something more irritating than nitrates. Maybe chlorine? Maybe phosphates? Maybe silicates? Maybe something terrible like copper? Maybe a combo of all those things?
Conventionally, there's no telling what that 1ppm is comprised of or whether that is TDS making its way past nearly-exhausted resin, or TDS leaching from the nearly-exausted resin (if the latter, the concentration of the substance(s) could be at greater concentration than what's found in the tap water it originated from).

I'm probably overly cautious and usually change out the DI resin once it registers at about 2ppm.
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Old 08-11-2010, 06:38 PM   #9
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Micky, with the unit sitting for that long you may have to recalibrate the TDS meter. There should be a small hole in the back of the unit to do that. If you plan to replace the DI resin, then I would wait until you did that then do the calibration.
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