Phosphorus in pool

Causes and cures for cloudy swimming pool water.
Milky pool water, white, pink, brown, purple, black cloudy water.
rn513
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Phosphorus in pool

Postby rn513 » Mon 25 May, 2009 08:30

Help!! My pool was clear but I was having low ph, total alk, and low chlorine problems. Over the course of 2 days I added ph increaser, sodium bicarb and shock per my pool store's advice. As soon as the shock went in my water turned green!! I brought a sample back the next day and was told to repeat chemicals that when ph is low sometimes water changes color. I asked for my water to be tested for metals and I think they only checked for iron which was neg. 2 days later we were still green. I brought another sample in and was told my water was perfect. Then they tested for phosphorus and it was positive. I bought 1 qt of seaclear phosphate remover and poured it in pool. My pool is blueish now but VERY cloudy. The pump has been running 24 -7 . It has been 2 days since I used the seaclear with no change in water quality. I also have used a clarifier. Does anyone have experience with this? Could there be something else wrong or does it just take a while for it to clear? Also, we have had rain everyday the past week! Thanks.


chem geek
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Phosphorus in pool

Postby chem geek » Mon 25 May, 2009 15:03

Phosphate removers precipitate phosphates in the water so can make the water cloudy initially. Phosphate removers and algaecides are unnecessary extra cost items since chlorine alone can keep a pool free of algae, but you need to maintain a Free Chlorine (FC) level suitable for the Cyanuric Acid (CYA) level. Read the Pool School for more info.

The cloudiness may also be a combination of high pH, TA and CH. Get a good test kit, the Taylor K-2006 or the TF100 from tftestkits.net, and use The Pool Calculator to figure out the saturation index which might also be high and that can have the water remain cloudy.

By the way, if you added a hypochlorite source of chlorine to the pool (e.g. Cal-Hypo, chlorinating liquid, bleach, lithium hypochlorite) and the water turned green, then you may have copper in the pool and should have it tested for metals.
Aquaclear-NZ
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Phosphorus in pool

Postby Aquaclear-NZ » Tue 26 May, 2009 02:54

Seakleer phosphate remover usually requires the use of a clarifier as well due to the nature of the product

we had the same problem here for a while when one of our chemical suppliers sent us some of that stuff branded as "ultimate phosphate remover" Service guys who were used to the other phosphate remover we had sold came back and complained tha the pools went cloudy
Chocolate fish do not swim in hot water
cjwalsh

Phosphorus in pool

Postby cjwalsh » Sat 26 Jun, 2010 20:34

Well then how do you treat it? I just was told that my phosphorus level was above the charts. I poured in what they suggested--looks like milk now. It was pristine--very clear-- before I poured this in. I have a salt water pool and the generator is not generating chlorine--true--told that it will not generate chlorine if the phosphorous is high. Now with treatment-it is very cloudy. Any suggestions?
chem geek
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Phosphorus in pool

Postby chem geek » Sun 27 Jun, 2010 02:12

If the cloudiness is only due to the phosphate remover, then you can use a clarifier such as BioGuard Polysheen Blue or even PolyQuat 60 will help clear the water. You should also make sure that your Free Chlorine (FC) level is at least 7.5% of the Cyanuric Acid (CYA) level if your pool is manually dosed with chlorine.
cjwalsh

Phosphorus in pool

Postby cjwalsh » Mon 28 Jun, 2010 18:19

rn513 wrote:Help!! My pool was clear but I was having low ph, total alk, and low chlorine problems. Over the course of 2 days I added ph increaser, sodium bicarb and shock per my pool store's advice. As soon as the shock went in my water turned green!! I brought a sample back the next day and was told to repeat chemicals that when ph is low sometimes water changes color. I asked for my water to be tested for metals and I think they only checked for iron which was neg. 2 days later we were still green. I brought another sample in and was told my water was perfect. Then they tested for phosphorus and it was positive. I bought 1 qt of seaclear phosphate remover and poured it in pool. My pool is blueish now but VERY cloudy. The pump has been running 24 -7 . It has been 2 days since I used the seaclear with no change in water quality. I also have used a clarifier. Does anyone have experience with this? Could there be something else wrong or does it just take a while for it to clear? Also, we have had rain everyday the past week! Thanks.
cjwalsh

Phosphorus in pool

Postby cjwalsh » Mon 28 Jun, 2010 18:27

Isn't it frustrating. My chlorinator won't work and I was told I had a very high phosphorous level. I used sea clear and the pool turned to milk. I also added the clarifier as recommended. Never the less I was nervous and called the pool company --they told me that using the product would turn the pool cloudy for about 7 days. I backwashed my pool after 24 hours and ran the filter for an extra 12 h. My pool is pristine now-I will know tomorrow if it helps. The problem I have is that the high phosphorous level in the pool is what is causing my chlorinator not to work--won't make chlorine from the salt. I was told it could not make chlorine if the pool has high phosphorous. Why I don't have algae is a mystery and my pool is very clean--maybe due to the phosphorous. Who knows. How did it get there who knows but I did have a lot of leaves in the bottom due to a leaky winter cover. I will keep you posted and good luck.
chem geek
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Phosphorus in pool

Postby chem geek » Tue 29 Jun, 2010 13:16

cjwalsh wrote:The problem I have is that the high phosphorous level in the pool is what is causing my chlorinator not to work--won't make chlorine from the salt. I was told it could not make chlorine if the pool has high phosphorous. Why I don't have algae is a mystery and my pool is very clean--maybe due to the phosphorous. Who knows. How did it get there who knows but I did have a lot of leaves in the bottom due to a leaky winter cover. I will keep you posted and good luck.

This is simply not true. A high phosphate level does NOT prevent the chlorinator from working. What it does is allow algae to grow faster since phosphates are an algae nutrient (as well as a nutrient for bacteria as well). When algae (or bacteria) first grow, they may not be visible initially but they can create a large chlorine demand that is more than the chlorinator can handle. You need to get ahead of this growth by shocking the pool to kill the algae faster than they can grow (in spite of the phosphates) and then maintain a proper Free Chlorine (FC) level which is a minimum of around 5% of the Cyanuric Acid (CYA) level in an SWG pool. However, this isn't what happened in your pool if I understand that you are opening the pool after having no FC in it over the winter...read on.

If your FC dropped to zero at any point for an extended time (at least 8 hours), then bacteria could have converted some of the CYA in the pool into ammonia and that can create a HUGE chlorine demand. Again, nothing to do with phosphates except that they allowed the bacteria to grow quickly. To prevent this in the future, you need to close the pool after the water gets cold (no higher than 50ºF) and shock with chlorine (and optionally add an algaecide such as PolyQuat 60) and then open the pool in the spring before the water warms up (no higher than 50ºF). Ideally, maintaining the FC level over the winter is best, but if the pool freezes over then this may not be practical so shocking beforehand and having the water be cold to slow down bacterial growth will work.

Were you initially keeping a 1-3 ppm FC with 80 ppm CYA as recommended by some SWG manufacturers? If so, then this is not sufficient and was the cause of the original problem. You need to maintain an FC of around 4 ppm if your CYA level is 80 ppm.

You should have your own good test kit for determining FC and CYA levels as the pool store does not always do the CYA test correctly and test strips are not accurate. Get yourself either the Taylor K-2006 or the TF-100 with the latter kit having more volume of reagents so is comparably priced per test. Please read the Pool School for more info on how to maintain your pool.

If you know that your CYA level has dropped and that this occurred when your FC was zero for some time (and it sounds like this might have been the case since you were opening your pool after it was "let go" for the winter), then you can get an inexpensive ammonia test kit from a fish/pet/aquarium store. It will take around 8-10 times the ammonia reading as cumulative FC to be added to get rid of it, but could take more chlorine than that before you get FC readings in the pool due to partially oxidized CYA that doesn't register as either CYA nor as ammonia. You can do a bucket test to see how much chlorine it will take before you get an FC reading. 1/4 teaspoon of 6% bleach in 2 gallons of pool water is 10 ppm FC so you can figure out how much cumulative FC it will take to clear your pool. Add the bleach, mix, measure again in 10 minutes, if the FC is near zero, add more chlorine and repeat. If FC is measured, wait an hour and see if it is holding; if not, add more chlorine and repeat.

The bacterial conversion of CYA into ammonia is described technically in this post while my own experience with this phenomenon is described in this thread .
orion77

Phosphorus in pool

Postby orion77 » Thu 28 Apr, 2011 16:39

chem geek writes: "This is simply not true. A high phosphate level does NOT prevent the chlorinator from working."
I don't know about a "chlorinator" not working, but we have been told by our pool supply contractor (expert?) that high phosphates are locking our chlorine so that it will not release as it is supposed to. If we test where our water comes out of the chlorinator as it enters the pool we will show 3.0 for chlorine but in the main body of water it will be 1.5 or less. After using Phosfree we will again have 3.0 throughout the pool until our phosphates get over 100 again. In the meantime, once we introduce Phosfree we have the cloudy water problem for about three days until we can get everything vacuumed from the pools. We are a large, luxury condominium in Hawaii and have three pools of between 69,000 gallons up to 74,000 gallons. All other chemical levels are at their optimum ranges. Seems like the problem with phosphates is much worse in our hot, summer weathe than in cooler weather. Bather load has not changed since before installation of the ChlorKing salt chlorinator. Any ideas on why we cannot get over the continual peaks and valleys of high phosphates???
chem geek
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Phosphorus in pool

Postby chem geek » Fri 29 Apr, 2011 01:28

Your pool supply contractor is wrong and is no expert, at least not about the relationship of phosphates and chlorine. High phosphate levels do not lock up chlorine -- there is NO chemical reaction between chlorine and phosphates period. High phosphate levels can allow algae to grow faster than chlorine can kill it IF the FC/CYA ratio is too low but the algae growth rate is ultimately limited by temperature and sunlight. Such algae may not even be visible yet (i.e. it's in the water growing, but not clumped up enough to make the water cloudy or green) but the growth can consume large amounts of chlorine.

As for chlorine levels coming out of the return vs. in the bulk pool water, it's SUPPOSED to be higher coming out of the returns -- that's what adds chlorine to the bulk pool water. The level in the bulk water will NEVER be the same as coming out of the returns with the SWG on unless the SWG is broken. Did you measure this yourself and did you ensure that the SWG was actually on when it was measured (the SWG usually has a percentage on-time so you cannot assume it is always producing chlorine)?

For example, if the chlorine demand (usage) were 0.25 ppm FC per hour, then even with the SWG on 100% of the time during this chlorine demand and assuming a 5-hour turnover rate, this means the SWG has to output 1.25 ppm FC over 5 hours (one turnover) to keep the bulk pool water FC constant. That means the FC out of the returns has to be 1.25 ppm higher than the bulk pool water. If the SWG on-time is less than 100%, then the FC out of the returns would need to be proportionately higher (50% on-time would need to be 2.5 ppm FC higher than the bulk pool water). So if you are really only seeing 3 ppm FC from the returns (at low phosphate levels) when the bulk pool water is at 3 ppm FC, then the chlorine demand is very low (unlikely if the pool is exposed to sunlight or has many bathers) and/or the turnover rate is exceptionally high or the test was not done correctly. Just think about it -- the SWG ADDS chlorine above that in the bulk pool water. If with higher phosphates in the pool the SWG is able to add 1.5 ppm FC to the 1.5 ppm FC in the bulk pool water to come out as 3 ppm FC from the returns, why is it that with low phosphates in the water it is apparently unable to output a higher FC level than the bulk pool water? Perhaps with low phosphates, the sample from the returns was measured when the SWG was off, possibly because the on-time was lowered below 100%.

Because you are finding a higher chlorine demand when the phosphate level rises, this means that your FC/CYA ratio is too low to kill algae faster than it can reproduce. When chlorinating with an SWG, the Free Chlorine (FC) level must be at least 5% of the Cyanuric Acid (CYA) level in order to kill algae faster than it can grow even at high phosphate levels, and that assumes good circulation throughout the pool. That means 4 ppm FC with 80 ppm CYA, for example. If you are only at 3 ppm FC, then if your CYA level is higher than 60 ppm then algae will grow faster than chlorine can kill it and you'll start to get behind as soon as there are enough algae nutrients (phosphates, nitrates) for the algae to grow more quickly.

I had 3000 ppb phosphates in my own pool and there are many others with high phosphate levels at Trouble Free Pool and The PoolForum who have been able to maintain their pools algae free and without unusually high chlorine demand simply by understanding the FC/CYA relationship (with manually dosed pools, the minimum FC is 7.5% of the CYA level). There is no question that at high phosphate levels the pools are more "reactive" in that IF you let the FC/CYA ratio get too low, then algae can grow rather quickly (though still takes days), but if maintaining the appropriate FC for the CYA level, then the algae simply will not grow.

You need to 1) lower your CYA level if it is too high -- it shouldn't be more than 80 ppm and if the pool has high bather load as with commercial/public pools then the CYA doesn't need to be that high where even 30 ppm may be enough, 2) the pool needs to be shocked with chlorine (i.e. raise the FC level) to kill off all nascent algae growth, 3) maintain an FC appropriate to the CYA level which may mean getting a larger sized SWG system to handle peak demand during the hottest sunniest weather.

Yes, if you want to you can spend more money on algaecides or phosphate removers on a regular basis in order to be able to maintain a lower FC level relative to CYA and still keep algae growth slower so the SWG can keep up. If you want to inhibit algae with one-time doses rather than weekly maintenance, then you could use 50 ppm Borates in the pool if not restricted by your state regs or you could use copper ions in the pools, but for copper beware of metal staining (especially for plaster or fiberglass pools; for vinyl, it's less of an issue).

How did you chlorinate the pool before installation of the saltwater chlorine generator? It sounds to me like they undersized the system and are using other excuses rather than fessing up. I'm sure the phosphate levels may have climbed earlier before installation of the SWG yet you were able to keep algae at bay. By the way, are you using metal sequestrants? Some are phosphate based. I'm just wondering why the phosphate levels are climbing in your pools. Do you have fertilized soil blowing into the pool?

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