Nanofiltration of my fill water. What is up with that?

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It's pooler in AZ

It's pooler in AZ

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Nov 4, 2010
33
I need to filter 7 to 10 gallons at 85 PSI per hour worst case during the summer to remove minerals. Any Chemist or Water Treatment expert out there that can help an Electrical trained guy out. My head hurts from four hours of internet search. I am just looking for a filter I could change two to four times a year to reduce my Mineral buildup in my pool.
 
OK, my evaporation rate on my pool is about 1.2 of its volume per year. Hence I have a mineral build up in my pool. Nanofiltration technology seems to be a growing field in water treatment and a simple filter system on my fill line would solve my mineral build up problem. I am not looking for a RO type system, just a cartridge filter with a low price.
 
for permanent installations, there are places like this and this

I have not purchased anything from these places, if you do, let us know your experience and what you selected.

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Can you provide us test results of your fill water? That will help greatly in the advice you need.

Typically the quantity and the flow rates of those type filters are the limiting factors and if you really lose 1.2x volume that's going to take a pretty good sized filter.

1.2x your volume is about 2100 gals a month or about 70 gallons a day. With a capacity of about 300 gallons per set of filters you're gonna be replacing filters every week. That works out to about $4000 a year for filters. It'd be a lot cheaper to have a R/O treatment done a few times a year.

I'm not trying to scare you off I just want you to be prepared. Granted, what I just gave you was a worst case scenario but not out of the realm of reality.
 
The highest level of Calcium from my city water report is 100 ppm and the lowest is 18 ppm. Water hardness is shown at 240 to 275 ppm for my area.
My CA just tested at the kitchen tap at 160 ppm and last spring when I drained and refilled the pool my initial CA reading was 140 ppm.

My pool is 21,470 gallons and at a 1.2 percent evaporation rate that adds up to 25,764 per year turnover. Using a worst case ball park guess that this evaporation happens during the summer six months I come up with:

25764/6/30/12 = 11.926 gallons per hour for 12 hours a day of sunlight. 11.926 divided by 2 for 24 hour a day filter operation brings it to a worst case flow requirement of 5.963 gallons per hour.

So maybe I am looking for a Nanofiltration filter that has a maximum flow rate of 7 gallons per hour and can handle the hardness build up so I would have to change it maybe four times a year at 50 US dollars a piece.

Am I asking for to much?
 
I would have several questions with this: How do you intend to produce the 85 psi you need? Where will you put the waste water associated with this process? What additional run time would you require of an additional pump (assuming that is your thought for achieving 85 psi) to maintain this?

I don't know where you are in AZ, but I have not experienced 18 to 100 CH in any part of AZ. If that is accurate, and even with your pool completely evaporating in a year, you would still easily be within standards (200-400 ppm calcium) for a plaster pool, of which you are not given the tap water parameters you state.

High psi, limited recovery of good versus bad water, additional pump, longer run times and somewhere to dump the brine solution all limit this idea. Why not just call Calsaway (http://www.calsaway.com) and have them R/O the pool every 2-4 years for a $300-$400 bucks or so and be done with it? I think you'd be money ahead in he end and not have a bunch of stuff at your equipment pad to worry about.

Just my .02
 
Thank you again for responding. I am going to call Calsaway in the spring and am very much looking forward to it. In the early hour of the morning I was reading about water softeners and came across Nanofiltration filters, a subject I know very little about. I am wondering if there is a filter out there that can be used in a non RO application. Just as a filter with no water loss or bypass.

The 85 psi is the water pressure at the fill valve for the pool.

The highest level of Calcium from my city water report is 100 ppm and the lowest is 18 ppm. Water hardness is shown at 240 to 275 ppm for my area. This did not seem right to me but that’s what it says.

Here is the link.

http://www.scottsdaleaz.gov/Assets/Publ ... Report.pdf

I have read that pool water evaporates at 8.5 feet a year in my neighborhood and my average pool depth is about 7 feet hence 1.2 turnover a year about
My CA just tested at the kitchen tap at 160 ppm and last spring when I drained and refilled the pool my initial CA reading was 140 ppm.

I am just wondering about Nanofiltration filters and its application in the pool industry.
 
Click on Bruce's link above, RO is part of his business as you may have grasped from his post there isn't much between the nano and RO. The TA of my fill water is 240-260ppm and it isn't a major problem just a bit more acid than I would like
 

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IpiA,

With those test results on calcium, you should have little to no buildup in your pool.

Just guessing, but it sounds like you may have let your pH get extraordinarily high over a long period. If that's the case, you can control your water parameters of CH, TA, and pH and never have to worry about removing any calcium.

What is your current pH and TA? How often do you test for them?
 
From June to November of last year my CA rose from 220 to 430 due to my evaporation loss of water. I do not have a scaling problem just a rising CA projecting to be around 650 to 700 this September. I know I can let it rise, RO it, or drain and fill.

My question is concerning the advances in Nanofiltration filters lately and their use in filtering my pool water before it is put into the pool. But not in the RO Method.

Since you asked my pool chemistry is PH - 7.6, ALC - 90, CL - 5+, CA - 430, CYA - 50, Borates - 55, and temp about 55. My water is rarely out of balance.
 
Personally, if it were my pool, I would use a white or very light colored reflective opaque cover. That will stop evaporation while reflecting most of the light to keep the pool from heating up, which I would presume would be a problem with hot Arizona summers. For convenience, an automatic electric safety cover could be used instead of the manually rolled-up bubble-type cover (that I'm not sure you can get in white/reflective anyway).

The main downside to a cover is that you need to either clean it off before opening or need to regularly clean out the "vault" where the cover rolls up. I believe you may get a lot of sand in the desert from winds.
 
Might even consider one of the liquid pool covers, unless you have a lot of wind, like chem geek says.

I do not understand how your CH can rise so fast with such low fill water levels. I evaporate close to what you do (a bit less) and I do not see as great a rise as you are suggesting. Something just seems off here.
 
Nano filtration is similar to RO, but less expensive, has lower water loss, and less complete filtration. In a pool situation, the main problem with both RO and nano filtration is water lost keeping the membrane from getting fouled/scaled with calcium and other minerals removed from the water.

If I am following what you are trying to do correctly, filter out the calcium from your fill water as you refill the pool, you might lose 25% with nano filtration, compared to 50+% with RO. Nano filtration clearly beats RO here, but that kind of water loss is still fairly large. That water loss might be acceptable to you, obviously that is a personal decision, but I don't see the point. Occasional commercial RO treatments (which use large and expensive filters that are much more efficient that what you could build for any reasonable price) are most likely to be significantly less expensive in the long run.
 
50-75% with typical R/O, just for clarification. We recover about 85%, and Calsaway should be well above 50% recovery also.

Just don't want anyone to think that "real" R/O cannot recover reasonable amounts of water. The little under the counter units are huge water wasters, but that is not true with larger units.
 
Thank You all, Jason you answered my question. I was hoping for a non bypass Nanofiltration system. It looks like it is not made for my size pool and wallet.

Chem Geek, I do use covers from time to time and yes the dust on the cover is the main reason I do not like to use them.

Simicrintz, I am definitely going to visit you store. Thanks again.
 
As a last word I could not find a Nanofiltration system in my price range, so I am staying old school. I did find one thing that would be interesting to try in a small pool or spa environment. It is a RO system that connects to both the hot and cold water feeds and returns the waste water to the hot line creating a zero waste RO system. In my case I would need about seven of them and filter replacement on top of the $ 2,000 up front makes it a no go for me. But, for a small pool or spa in other parts of the world maybe something to think about. Below is the link.

http://www.watts.com/pages/_products_de ... p?pid=5595
 
That (those) units are made for indoor use, and have a maximum TDS of 1,800. I'm not real sure that would work outdoors or handle typical pool water chemistry (especially salt pools), and would probably not be warranted for such.

Did you find anything that explained the "zero waste"? I don't know how you can remove something and not take it somewhere, so that makes no sense to me, especially in a closed loop system, like a pool. It's gotta go somewhere!
 

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