Phosphates and cloudy water

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E

ETS

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In The Industry
Apr 22, 2009
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Can phosphates alone cause cloudy pool water? If so, under what circumstances does that occur? Not counting the use of phosphate removers.

"Phosphates are excellent plant fertilisers. They do no detectable harm in humans (in fact, phosphorus is an essential element for all known life). However, many phosphate salts are insoluble and form very fine precipitates. If the metals that combine with the phosphate are calcium or magnesium, the precipitate will be white, and if it is finely dispersed, the water will take on a cloudy appearance.

Filtration won't work on this type of cloudiness, because the solid has very fine particles. Your best bet would be to either drain, clean and refill the pool, or to add a coagulant that will precipitate the phosphate completely, and then remove the settled solid. Ask at a specialist store what would be the best option."

I found the above quote in answer to a cloudy pool question on "yahoo answers" The answer came from someone claiming to be a doctoral student in analytical chemistry.

Can anyone verify this or refute it?
 
I can only verify that this forum generally ignores phosphates and thousands of us maintain crystal clear pools thropugh proper chlorination. That doesn't answer your question, tho. Others will be along soon who may provide a more definitive answer.
 
Thanks duraleigh, for your response, none the less.

I'm posting this because of what happened in our pool store today. I was testing a customers' water who was complaining that it was cloudy. I was told by a colleague to test his phosphates. I replied that I was not concerned about that. He said that I should be. I said no, phosphates do not cause cloudy water. He called me ignorant (not in those terms) and he immediately jumped on the internet looking for info to prove me wrong. Hence the quote in my first post.
 
It would be easy to blame phosphates as the cause, but I'd be willing to bet the cause is the pool owner is not maintaining the proper FC to CYA ratio and they have a nascent algae situation. Sure phosphates may be present but if they were keeping the FC up to the proper level it wouldn't matter.
 
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ETS, you're stuck between a rock and a hard place.

You know that phosphates are not the problem. You know it because you are here at TFP. So test for phosphates when you are at work. Do it because it is expected of you. You know better, that's true. But you have to pay the bills and therefore, you have to work. So give them their phosphate reading and other results. Lean over the counter and tell the customer in a soft voice as you circle the phos reading, "ignore this". Then, show them where the products are that can actually help them fix their problem. There! That was easy! :mrgreen: :goodjob: :mrgreen:
 
Very high phosphate levels along with high CH levels can precipitate calcium phosphate and some calcium reducers are based on this principle. Also, phosphate buffers added to water that has CH will cloud and reduce CH levels as well and this effect is exacerbated at higher pH. However, the phosphate levels for this effect to occur are usually higher than the phosphate levels in most pools unless a phosphate buffer was intentionally added (this is more common in spas which sometimes use phosphate buffers) or unless the pH gets very high.

After all, if normal CH levels were to precipitate phosphate, then the phosphate levels wouldn't get very high in pools to begin with and the industry of phosphate removers wouldn't have anything to market. I know that for my own pool when it had 2000-3000 ppb phosphates, that it wouldn't cloud up when the pH got to 7.7 and I don't think it would cloud up even at a pH of 8.0 either. So the level of phosphates and CH where cloudiness would occur is probably quite high. Someone else on this forum (JohnT or JasonLion, I believe) has even higher phosphate levels and don't get cloudiness though I don't remember their CH or pH.

The more common scenario with cloudiness in pools with high phosphate levels is that algae grows quickly due to the nutrients available (i.e. phosphates and probably nitrates). Early algae growth often looks like dull or cloudy water before it eventually turns into a full-fledged green algae bloom. However, as you know, maintaining a sufficient FC relative to CYA is all that is needed to kill algae faster than it can grow in spite of the phosphate level. If the pool is cloudy, one should shock the pool to get ahead of such growth and thereafter maintain the appropriate FC/CYA ratio based on the Chlorine / CYA Chart.
 
Thank you all for your responses and support.

I had told the customer that his cloudy water was most likely caused by a nascent algae bloom due to his water test showing FC = 0 and a PH = 8.0 or higher. All other readings were normal.

My colleague has no authority to tell me how to do my job. However, he has enormous influence over the owner with his impressive experience and credentials, not to mention his domineering personality.
So, if I don't have hard evidence to counter him we will soon be selling phosphate remover to every customer that comes in the door with cloudy water. That will be disastrous to our business.
 
Because of what phosphate removers can do to the water! Make it even cloudier!
If you sell to pool owners (with cloudy water), a product that makes their water even cloudier (even if it's only temporary) they are going think you are crazy and go somewhere else to get their water tested. And no amount of explaining will stop them.
 

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What if you did as he suggested, test for phosphates. If the result came back high, say over 1,000 (not sure what constitutes "high").... you can explain that they are algae food, but if they maintain the proper FC ratio, it won't matter, or if they would like, use phosphate remover, but it might cause the clouding to get worse, albeit temporarily. Give them a choice, (a) shock the pool because it's probably nascent algae and then if they like they can use the phosphate remover, though it's optional. Would that satisfy him? Sorry that's quite the bind you find yourself in.
 
The "Internet source" was from Yahoo Answers here which is hardly authoritative. The answer wasn't untrue, but at the level of phosphates and CH and usual pH found in pools, it may not be applicable.

If the cloudiness were due to either calcium phosphate or calcium carbonate precipitation, then lowering the pH should clear it up. So in any event, lowering the pH from 8.0 to 7.5 would be the proper prescription to start with. Having zero FC is also obviously a problem so adding chlorine would also be required, probably at shock level, though lower the pH first since a hypochlorite source of chlorine will tend to raise the pH (so perhaps lower the pH to 7.2 if the shock level needs to be high due to a high CYA level).
 
ETS,

I repeat this frequently on this forum. A prime tenant of BBB is that you simply don't put things in your pool you don't need.

A properly chlorinated pool will not need phosphate remover regardless of any side effect that may or may not occur.

If you don't need it, why would you use it? Your boss may have a different outlook in that he needs to make a profit in order to pay you money so you have to walk a pretty fine line to work in a pool store and subscribe to BBB methods. It's not impossible but you have to tread lightly.

Lastly, your co-worker possesses all the ignorance, not you. You have learned pool water chemistry and he has not....at least not correctly. You'll likely never be able to teach him because the answers are readily available to him and he apparently chooses not to learn.
 
ETS said:
Because of what phosphate removers can do to the water! Make it even cloudier!
If you sell to pool owners (with cloudy water), a product that makes their water even cloudier (even if it's only temporary) they are going think you are crazy and go somewhere else to get their water tested. And no amount of explaining will stop them.
Click to expand...

There are obviously differences between manufacturers, the one I use does not make the water cloudy as it is partnered with a good polyfloc. A chance for the shop to make another sale and act pro-actively.

Of course you could just tell them they don't need it as many on here will testify, as long as you don't get the sack.
 
My phosphate level is currently down to perhaps 2,000, having topped 4,000 a few years ago, and I have never had any problem maintaining crystal clear water.

My phosphate level varies for year to year, but is always quite high. The local water company adds quite a bit of orthophosphate to the water to help prevent lead from leaching into the water (which caused a big problem a couple of years ago). I happened to be replacing most of my water just when they had the orthophosphate level extremely high attempting to get rid of the lead as quickly as possible. Since then they have lowered the amount orthophosphate added to the water noticeably, but there is still quite a bit.

I have found that I need to maintain an FC level around the target level from our SWG CYA/Chlorine table. If I let FC go down to the minimum there is a slight loss of clarity (very slight, still clear just not sparkling) and dead algae rains down on the bottom of the pool slowly, but obviously. I tend to assume this slightly elevated FC level is required because of the phosphate, though it is of course difficult to prove that.

I tend to keep TA low, around 60 to 70, PH around 7.5 to 7.6, CYA around 70 to 80. CH has varied somewhat, currently around 50, but a couple of years ago it was closer to 150. Daily chlorine consumption averages around 0.5 ppm. The pool is surrounded by tall trees, which shade the pool from direct sunlight most of the day.

Just for fun I tried a phosphate remover last year. It clogged the filter almost instantly twice in a row and turned the water somewhat cloudy for about a day. I have a sand filter that can normally go a month between backwashes. The phosphate remover appears to have removed some phosphate, but didn't make much of a dent in my phosphate level.

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It is very common for others here at TFP to report phosphate levels around 500 to 1,000 and extremely clear water. Phosphate levels above 1,000 aren't very common, and aren't easy to test for, so we have less experience with them. Still, there have been a couple of other examples of pools with phosphate over 1,000, and none of them reported any problems or any particular trouble with maintaining water clarity (at least once the unrelated problems that brought them here in the first place was solved).
 
Hmmmph. Algae food... algae water... algae clothes... algae car and college... algae buddies dropping by and emptying the fridge and breaking the coffee table...

If you don't have algae, you don't have problems with that stuff.
 
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