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Thread: Reverse Osmosis for pool filtration?

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    Reverse Osmosis for pool filtration?

    Okay, I know this question has been asked before, but I can't find any information about this because of all the "RO Treatments" available to people instead of a drain/fill.

    I have a pool in Cape Coral, FL. It is about 20,000 gallons. Like everyone else in the world, my wife and I don't like chlorine. We have looked into "swimming pond" conversions, as well as a lot of "chemical free" solutions that mostly seem like snake-oil.

    In my business, we use a cheap ($1,000) reverse Osmosis unit that can produce about 2,500 gallons per day. My question is, could a unit like this be used on a pool to continuously or semi-continuously filter the water? The membranes and pre-filters should last an extremely long time once the pool is filled, as it would just be re-filtering RO water with the small amount of contaminants that make it into the water. The pool is covered and in a tightly screened area, so very little debris will make it in. There would never be children or anything else soiling the water beyond what happens just from going swimming. The system would also be "closed", meaning that the source of the water would be the pool (via a booster pump), and the output and wastewater drain would both empty into the pool.

    I see a lot of advantages to swimming in RO water as well, since there are no minerals in it. RO also filters out bacteria and viruses very effectively. The water would also be almost completely free of organics for algae/bacteria to grow from. Theoretically, no type of complex organism or insect should be able to live in it, either.

    I expect there is a perfectly valid reason why this isn't viable, and I'd love to hear it . I've never owned or maintained a pool before, so I am sure I am overlooking something.

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    Re: Reverse Osmosis for pool filtration?

    If you don't like chlorine, maybe you haven't been in a properly chlorinated pool. You wont smell it, taste it, or feel it.
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    Re: Reverse Osmosis for pool filtration?

    One turnover every seven days? What is going to kill the Algae spores that get into the pool while they are waiting their turn for RO? Your approach allows organic matter to continually grow in the pool.

    Your pool needs a sanitizer and an oxidizer. Chlorine does both. I suggest you read Pool School and see our approach to pool sanitation.
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    Re: Reverse Osmosis for pool filtration?

    Wouldn't algae/etc grow slower in RO water? I understand it would accumulate over time via spores/etc, but I wouldn't think it would happen faster than the filter could take it out.

    The wastewater would be recycled into the pool. Since the feed water is already filtered by RO, there's very little work for the membrane to do. Any particles are filtered out before the membrane by sediment filters. I can get a 40" membranes very, very cheap.

    Is there any reason not to use a Reverse Osmosis system to start your pool, even if chemicals are used?

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    Swampwoman's Avatar
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    Re: Reverse Osmosis for pool filtration?

    Gwegan, R/O is appropriate water treatment for pools where the cya or calcium has gotten too high...and for this reason among others is NOT appropriate for day-to-day pool maintenance

    For example in your case with a pebble sheen finish...if you were filtering with r/o you would remove te calcium you need in the water to protect your finish!

    In terms of sanitation, it would also fail by virtue of speed alone, even if it could theoretically remove contaminants...chlorine kills most waterborne pathogens almost immediately. Seconds versus days

    While you might not like to think about it, small amounts of urine, mucous and even trace amounts of fecal matter regularly contaminate water when people swim (and I don't mean just kids.) Frankly, swimming without adequate chlorine is pretty much like sharing a big bathtub with a load of your friends...and then getting into that same bath water the next day...except te bath water starts out chlorinated!

    R/O however, is a good way to recover water that would otherwise be dumped due to high cya or calcium, and ergo is environmentally astute, especially where water conservation is an issue.

    But even pro R/O companies won't filter water with algae because it fouls the membranes. So once again r/o would like fail you on algae control and cost efficacy due to mechanical speed and mechanical fouling.

    So in terms of sanitation and algae control plus water balance to maintain finish, r/o would be a bust, I'm afraid.
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    Re: Reverse Osmosis for pool filtration?

    As swampwoman said, if you have and maintain zero calcium in your water it is going to destroy your pool finish. So right out of the gate you cannot do this, period. Next, there is always something falling in a pool, even if unused. Dirt, dust, bird droppings, etc. RO will be very slow to filter that out given your turnover time. Finally you are ignoring bacteria, RO won't do much for that.

    I believe if you really want to make a more comfortable pool with less of the issues you attribute to chlorine then you will be best suited by learning more about pool chemistry here. The methods taught here lead to pools that lack most of the comfort and maintenance problems associated with a typical chlorine pool. Thousands on here can vouch for the difference it makes and, unlike continuous RO treating, will be sanitary and won't destroy your finish.

    [EDIT] I want to make sure I make it clear, I am 100% not attacking you or your idea. New ideas are good, just a lot of them, this one included, does not stand up to scrutiny. I do hope you take the same problem solving attitude you have used to come up with this idea and use it to pursue TFPC for your pool. It really is the ultimate DIY fix to most of the reasons that make you say you don't like chlorine.[EDIT]

    And welcome to TFP!

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    Patrick_B's Avatar
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    Re: Reverse Osmosis for pool filtration?

    Well, I wanted to answer, but it's all pretty much been covered. RO for a pool, is neither good, or practical. And not matter what, it still needs sanitation.
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