Going R/O - The Planted Tank Forum
 
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post #1 of 13 (permalink) Old 05-28-2009, 08:40 AM Thread Starter
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Going R/O

I want to start using R/O in one of my tanks. From what I have read here pure R/O is a no no. SO I plan on mixing it with tap water.

I have decided to use R/O because I believe that some of the species of plants that I have tried to grow have died as a result of the liquid rock that pours out of the tap here. Now that I have decided to go through the hassle of mixing R/O water with tap I was wondering what would be a good GH / KH range? I would like the water soft but also some what stable.

Thanks,
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post #2 of 13 (permalink) Old 05-28-2009, 08:41 AM
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What are your tap water parameters? pH, gH. kH.
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post #3 of 13 (permalink) Old 05-28-2009, 08:42 AM Thread Starter
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PH - 7.8
GH - 35d
KH - 17d
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post #4 of 13 (permalink) Old 05-28-2009, 08:48 AM
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Quote:
Originally Posted by filipem View Post
GH - 35d
LOL!

Are you sure that gH is that high? Since your kH is "only" about half that.

Mix 1:4 RO:tap and retest your water parameters and post them up.
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post #5 of 13 (permalink) Old 05-28-2009, 08:54 AM Thread Starter
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LOL yes it's late and I'm a little tired.

Yes I'm sure it's right I've tested the water using several sources. African cichlids love the water. Plants and SA's on the other hand do not fair so well.

Thanks I'll post them when I get the numbers.
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post #6 of 13 (permalink) Old 06-11-2009, 10:02 AM
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I use pure RO. I tried adding a little tap but I had more algae problems. Water here is liquid rock.
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post #7 of 13 (permalink) Old 06-11-2009, 11:59 AM Thread Starter
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my readings

GH - 0 (also using a new water softener
KH - 6ish
TDS - 100ppm

is the normal? the carbon, membrane, and sediment filters are all new.

I was expecting lower readings....
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post #8 of 13 (permalink) Old 06-12-2009, 07:30 PM
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R/O works better under pressure
You may want to get a "booster pump" to increase membrane efficiency
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post #9 of 13 (permalink) Old 06-12-2009, 07:38 PM
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You also have to rinse whatever you are testing in about a dozen times. TDS just says there are total dissolved solids, it doesn't say what kind. A plastic baggie works well, generally pretty clean. The TDS from my RO/DI is 0, RO is about 4.
You should also have a flush kit on your unit. And let the water run for awhile after flushing{don't take the first water out to test}
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post #10 of 13 (permalink) Old 06-12-2009, 07:45 PM Thread Starter
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That explains a lot. My water pressure is low. I've looked at buying a booster pump but the ones I've found are very expensive. Anyone know where I can buy one at a reasonable price?

I do have a flush kit on the unit but I haven't allowed the water to run after I've flushed. I also don't really rinse the tubes that well.

That would explain why my readings are high.
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post #11 of 13 (permalink) Old 06-12-2009, 10:15 PM
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Flush it once a week too.
Are you using a handheld meter to test, or going by an inline? I don't trust inline TDS meters. I use a Hanna. Where did you purchase your new filters? {this is not a new unit correct?}The quality of filters is not the same for drinking water, as it is for the hobby. I love these guys... their customer service, fast shipping, prices, and quality are top notch.
http://www.thefilterguys.biz/

Have you tested what your membrane is putting out before the filter? ie: maybe it's time to change the membrane. If you are getting readings higher than the 20's-30's past your membrane, then I would say it's bad too. Get a Filmtec, they are the best.
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post #12 of 13 (permalink) Old 06-13-2009, 06:09 PM
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Quote:
Originally Posted by filipem View Post
That explains a lot. My water pressure is low. I've looked at buying a booster pump but the ones I've found are very expensive. Anyone know where I can buy one at a reasonable price?

I do have a flush kit on the unit but I haven't allowed the water to run after I've flushed. I also don't really rinse the tubes that well.

That would explain why my readings are high.
When I bought my RO unit, I knew nothing and hoped it was just a matter of plugging it in and letting 'er rip. Like everything in the hobby though, it's never that simple and usually involves complex, expensive solutions.

From what I know, I think most membranes flush as they make water. I haven't really seen or heard many people recommending flush kits. I don't think they're bad at all, I just think they probably don't have as much of a benefit as people think.

Also your readings don't sound normal, but that would depend on your input water. What's the TDS of your input water? With that, you can then calculate how efficiently your membrane is working. Let the unit run for a bit before calculating output water though. You get what's called TDS creep when firing it up. I don't think the cleanliness with your RO unit or filter housings have an appreciable effect on TDS.

I think you have the same problem as me. water pressure, water pressure, , water pressure, . Most membranes are rated at 96-98% efficiency. My water pressure is just shy of 40 PSI. My input water is 550 TDS, output is 50 TDS. If you crunch the numbers, that's 89% efficiency. I think both your and my situations, a booster pump would solve most of the problems. Higher water pressure would lead to a more efficienct membrane performance and increased water production. You can tweak things to raise the performance a bit (a better membrane etc.) but you won't have much luck without a booster pump.

I looked around on eBay for awhile, and I found an aquatec 8800 for about $110 shipped. They have some cheaper units that range from $75 shipped to $95 shipped, but they all looked a bit sketchy. Everyone recommends the aquatec pump. Being a college student, I nearly exceeded my aquarium budget already by buying the RODI, but the aquatec may become my next investment. The best way is to charge it on CC at the beginning of your statement period, and you have 30 days to relax and not look at the bill before curling into a ball and crying.

But seriously, for low water pressure, a booster pump is about the only viable option to fix membrane performance.

Chris
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post #13 of 13 (permalink) Old 06-14-2009, 03:18 PM
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Quote:
Originally Posted by NyteBlade View Post

From what I know, I think most membranes flush as they make water. I haven't really seen or heard many people recommending flush kits. I don't think they're bad at all, I just think they probably don't have as much of a benefit as people think.



.
They extend the life of your membrane. The flush kit increases the pressure and makes the water flush the membrane clean. Ask someone who sells RO/DI units. I worked at a saltwater LFS for several years. I worked with my customers, and could see those who had them and did not use them, or did not have them. They would go through filters and membranes much faster than those who have them and use them.
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