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Less Minerals in swimming pool water

Removing Minerals from swimming pool water w/o drain and refill
 
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Problem:

Local water in San Diego has a high mineral content. After a year or so of water evaporating a couple inches and filling the pool back to full on a weekly basis, the mineral content is getting higher and higher. Draining most of the water out and starting over is not desirable. ( Doing nothing will make it a mud wallow or salt lick. he hee )

Possible solutions:

1. Covering with floating plastic to prevent evaporation.

2. Solar or other still to concentrate and separate the minerals for dumping.

3. Reverse osmosis to concentrate and separate the minerals for dumping.

4. Sell highly mineralized lemonade at roadside stand. "Now fortified with dead algae and baby urine!"

Any thoughts? Hot tubs get full of stuff faster and there is less to drain and fill, but pools are different.

popbottle, Jun 11 2013

Electrochlorination http://en.wikipedia...Electrochlorination
[4and20, Jun 16 2013]

Sediment and bio purification system http://www.youtube....watch?v=TG4lWEGYjQY
[pashute, Jun 21 2013]

Aquaponics explained in a beautiful system http://www.youtube....ch?v=VBspR2p0YYM&NR
[pashute, Jun 21 2013]

[link]






       1. Cover the pool, heat the water to a gentle simmer and sustain there until deposited minerals have dissolved. Drain hot water, with minerals in solution.   

       2. One could use the reverse of that to extract minerals before filling. I envision a system whereby water is chilled to just short of freezing, then drips into a reservoir and from there into the pool. Precipitated minerals are left behind as the drip forms, producing stalactites which with some forethought could be sold as art.   

       3. The solar still idea could be doable in San Diego. Giant Frensel lenses would make the project more youtube worthy.   

       4. The baby urine / dead algae scheme does have its charms, as well as supposed health benefits.
bungston, Jun 11 2013
  

       This seems to be more of a request for suggestions than an idea, if I may say so.
MaxwellBuchanan, Jun 11 2013
  

       You may say so. Suggestions welcome.   

       I spend time daily trying to keep a park pool usable. Last time pool was empty, it was re-plastered. The plastic floaty things, get in the way of swimmers. Need something to bake, that doesn't cost an arm and a leg.
popbottle, Jun 11 2013
  

       Simply add RO water each time...
Ling, Jun 11 2013
  

       Have you Googled for advice on this? You can't be the first one to face this problem. I just found one page that suggests that the way to get dissolved metals out of pool water is to add a “sequestrant” that binds to the metals and allows them to be filtered out. There are also apparently “descaler” products that serve a similar purpose for other minerals. You could also install a water softener.   

       This probably isn't the best forum for something like this, though. You might have better luck on a site for pool owners.
ytk, Jun 11 2013
  

       There is liquid film which can be added to pool water which retracts to the sides at a touch which will keep evaporation down.   

       It took three kicks-at-the-cat to get our above-ground pool nearly self-maintaining, (that is, as soon as I snake-out the pine cone I accidentally vacuumed up), I moved the pump system and filter beneath the deck so that it never needs to be primed and built a small roof-top/ black-pipe solar heater. An automatic vacuum runs off the pressure from the skimmer basket and cleans the bottom continuously but you sacrifice a skimmer basket so I installed a 90 degree floating in-flow skimmer, and the whole thing works without using any more electricity than the pump uses anyway.   

       The minerals don't really build up on the sides much and they come out in the backwash sludge.   

       'luck.   

       I'd wager most of the crap in the pool is from people/pet's muddy feet, windborn dust and algae, not precipitated minerals from the mains water.   

       Very civic-minded of you taking care of a park pool.   

       How big is it ?
FlyingToaster, Jun 12 2013
  

       One can swing pH back and forth with not much fuss, even in a large body of water. I wonder if a radical change in pH would change solubility of salts such that they precipitate out. They could then be vacuumed up, then bring pH back to pool normal. Doing this with HCl and NaOH would just make the water a little saltier, and that is not as bad as the calcium and magnesium salts that build up.
bungston, Jun 13 2013
  

       //One can swing pH back and forth with not much fuss, even in a large body of water. I wonder if a radical change in pH would change solubility of salts such that they precipitate out.//   

       You can swing the pH of an unbuffered solution back and forth with not much fuss. But if you have salts precipitating out as the pH changes, they will tend to buffer the pH and you'll need to add a fair amount of acid or base.
MaxwellBuchanan, Jun 13 2013
  

       If you could filter out Les Miserables, you'd probably get richer.
not_morrison_rm, Jun 14 2013
  

       Wikipedia says electrochlorination leaves no sludge [link]
4and20, Jun 16 2013
  

       Thinking further - I suspect that alkalinization of the water will favor dissolving of calcium and magnesium scale. These deposits might be thick and it will take time. The higher the pH the less time.   

       Once in solution then what? If the pH is brought back to tolerable 7 they will precipitate out again, and probably once again on the sides of the pool.   

       I propose that cinderblocks, and a lot of them, could be added to the pool first. Maybe in a pyramid on the bottom. When the pH comes down to normal these blocks will offer lots of surface area for precipitation of salts. They can then be removed. The same blocks can be used over and over for this.
bungston, Jun 17 2013
  

       pH isn't a problem since he's using mains water. Y'all want to add Cl- up to 3-4ppm to kill off algae or pathogens, and alum to take the suspended solids (cloudiness) out.   

       Supplementary chlorine needs to be added because the pool water is warmer than the mains water, plus chlorine evaporates out.   

       Alum will knock any cloudiness right on its ass: it latches onto suspended solids making them large enough to sink to the bottom. But it needs to be mixed well then allowed to settle (say an hour); depending on the pond size you can do it yourself splashing around, subcontract to some kids and dogs, or use a pump to swirl water around. For weekly maintenance add the alum, wait, then vacuum up the sediment from the desuspension process.   

       [edit: I'm pretty sure you don't have to vacuum out the existing sediment before you add the alum since its reaction with SS's are electrostatic, ie: it won't latch onto stirred up particulates big enough to sink to the bottom on their own... but you should check: it's been more than a few decades since I've done water supply]
FlyingToaster, Jun 17 2013
  

       Alum certainly collected a bunch of stuff from a gallon of pool water I tested it on. All cloudy white and then a sort of sleepy ghost settled to the bottom of the jar.   

       Thanks y'all.
popbottle, Jun 20 2013
  

       I like "sleepy ghost"   

       I am a little concerned that you tried baking a suggestion you got from the half bakery.
bungston, Jun 20 2013
  

       'strue dat: my experience is from almost 40 years ago, using equipment 30 years older than that, for a completely different application. I mean, if you just happen to have a Brit No4 water purification set kicking around, I might be able to tell you how to use bits of it for your pond, but I'm not a pool guy.   

       Along those lines it'd probably be cheaper to use a filter and a pump first before adding alum.
FlyingToaster, Jun 21 2013
  

       Use it in a aquaponic type of system, with a "constructed wetland". See link.   

       The plants growing in the gravel, will be flowers and trees all around the pool.   

       The gravel - or actually the bio-system growing in the gravel, will clean the water at a low cost.   

       You could also make a set of pools that fills and decays and cover it with a few inches of sand. This would be a giant sandbox, that every 20 minutes has water coming up to the height of a puddle. Could be great fun, and will always stay healthful because of constant aeration.   

       Once in 50 years you would have to change the gravel, - send it to the sewage system, which has the means to recycle the water and take care of the minerals in an eco-friendly well thought out way.
pashute, Jun 21 2013
  

       I love the idea of pool with purging pond.   

       Toaster I read about alum after your post and it was very interesting. Used to clean water since the days of the Romans, says wikipedia. But I (like the water) am not clear: the the alum flocculate bits of organic stuff in the water or does it actually pull dissolved salts (calcium? magnesium? BORON??) out of solution?   

       In San Diego and elsewhere in So Cal there is some sort of white crystal that comes up from the ground in solution then leaves a residue when it dries. This stuff comes thru concrete and can come up into houses thru the concrete pad most are built on. It does not taste salty and is not that soluble - certainly not as much as salt. It is sort of like the deposits around Mono lake which also do not taste salty. I imagine this stuff must be calcium carbonate but I cannot imagine where it is coming from in San Diego - the geology there is sandstone and shale, not limestone. So where do the mineral salts come from?
bungston, Jun 21 2013
  

       According to WP, suspended solids don't sink because of their electrostatic charge. Deflocculants like alum stick to the particles and neutralize the charge, allowing them to drop.
FlyingToaster, Jun 21 2013
  

       So for poopicules and malicious microbes: alum. But how does alum address dissolved salts?
bungston, Jun 21 2013
  

       [Bungston] I'm guessing either you're sitting on shale with a high content of calcite, or it's coming in as ground water from the Santa Ana mountains, which do have some limestone.
MechE, Jun 21 2013
  

       [bungston] alum doesn't address DS's, nor microbes. It just sounded like [pb]'s problem was turbidity.   

       Here's an easy test: start with a clean'ish kettle, full of water. Boil it down to almost nothing and see if what you pour out is cloudy.
FlyingToaster, Jun 21 2013
  
      
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