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Thread: Have your water checked for phosphates and nitrates

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    Have your water checked for phosphates and nitrates

    This off topic side conversation has been moved into it's own topic. JasonLion

    True only way to lower cya is to drain and add fresh water have your water checked for phosphates and nitrates they eat up chlorine

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    Re: Have your water checked for phosphates and nitrates

    Quote Originally Posted by williamsonpools View Post
    have your water checked for phosphates and nitrates they eat up chlorine
    They don't actually do that. Neither phosphates or nitrates use any chlorine at all.

    There is a kind of tiny grain of truth here, but it is so distorted as to be meaningless. If the chlorine level is too low to prevent algae, you will get algae more quickly at higher phosphate levels, which can for a time show up as an increased chlorine demand before it turns into a full algae bloom. But in that kind of a situation, you are going to get algae eventually regardless (since chlorine is too low).

    As long as you maintain appropriate FC levels, you won't get algae and you won't have excess chlorine demand, regardless of the phosphate/nitrate level.
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    Re: Have your water checked for phosphates and nitrates

    Quote Originally Posted by williamsonpools View Post
    True only way to lower cya is to drain and add fresh water have your water checked for phosphates and nitrates they eat up chlorine
    Phosphates eat chlorine? Is this what the pool store told you?
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    Re: Have your water checked for phosphates and nitrates

    In my experience when a pool that I had just done maintenance on had turned green over night knowing I had just shocked and added pucks I would test it for nitrates and phosphates and 1 or the other would be high so in my terms they eat up the chlorine

    - - - Updated - - -

    How did this even get its own thread I was trying to give someone a suggestion on a problem

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    Re: Have your water checked for phosphates and nitrates

    My phosphate level is over 2,000. A few years ago it was over 4,000 (very very high). Yet my pool uses less chlorine than the average pool and I haven't gotten algae in years.

    Many many pools have high phosphate or high nitrate levels. Both are naturally occurring and frequently brought into the pool by pollen, high winds, leaves fall in the pool, etc. In some areas phosphates are even added to the tap water by the water company. Despite this, there are many many people who never test for either one and never have any problems. Sure, some pools have problems, and some pools have high phosphate/nitrate levels, and often enough those two groups will overlap, but that doesn't mean that the two have anything to do with each other.
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    Re: Have your water checked for phosphates and nitrates

    All I am saying last year working in maryland I had a couple of POOLs that turned green overnight and we could not get them to come back around we found high nitrates in the pool we drained water and refilled which lowered nitrates in the pool problem solved we came to the conclusion it was caused by a fertilizer the lawn people using

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    Re: Have your water checked for phosphates and nitrates

    It wasn't the nitrates. It was the fact that the FC was too low for the CYA in the pool. Period. No other cause. I suggest you spend some time learning in Pool School.

    Unfortunately, there is a lot of misinformation in the pool maintenance industry.
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    Re: Have your water checked for phosphates and nitrates

    Nitrates and nitrites are products of nitrogen gas. Nitrate which consist of a single nitrogen atom connected to 3 oxygen atoms(No3) is extremely stable or hard to remove. Nitrogen (No2) can enter your pool water from a variety of sources. It combines with oxygen to form nitrites (No2). This extra oxygen atom is not just floating on top of your pool (unless using an ozinator) so the aggressive nitrogen oxide will steal another o atom from our chlorine molecule HOCL. This makes our chlorine less effective and increases your chlorine demand. This continues as nitrites take to another oxygen atom to become nitrates (No3)

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    Re: Have your water checked for phosphates and nitrates

    Nitrates are stable in the water and not further oxidized by chlorine, so it is impossible for nitrates themselves to increase chlorine demand. Ammonia can cause high chlorine demand, but that can eventually be satisfied with enough chlorine. That aside, I think the major issue here is that the industry often proclaims the concept of "chlorine lock" which is essentially what is being discussed here without being actually named. The pools that turned green overnight ONLY turned green because they had insufficient chlorine, not because nitrates consumed the chlorine. Turning green means algae grew. Algae can only grow with insufficient chlorine, plain and simple. You can be surrounded by all the food in the world, but you can't eat and grow if you're dead from being surrounded by chlorine gas. Same goes for algae. You could have fixed the green pools with enough chlorine and no water dilution if you wanted, but proper and timely adjustment of pool chemicals would be necessary afterward.

    That being said, if you have people that are lazy with pool care, or if they are serviced only once per week, then you probably need additional means of keeping the algae under control. In that scenario, water dilution to lower nitrates makes sense as it can keep algae from growing as quickly during times of insufficient chlorination. On this forum, however, most agree that maintaining pool chemistry is best performed as a daily task which is simply incompatible with a weekly service. This is the root of many differences in the TFP method and industry method.
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    Re: Have your water checked for phosphates and nitrates

    Quote Originally Posted by williamsonpools View Post
    POOLs that turned green overnight and we could not get them to come back around
    In cases like these, it is almost invariably the CYA level being too high that causes the problem. If they indeed had high CYA levels, water replacement would be the only practical solution.
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    Re: Have your water checked for phosphates and nitrates

    So the consensus around here is that the presence of high nitrates does NOT Cause rapid algae growth

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    Re: Have your water checked for phosphates and nitrates

    Not if there is sufficient chlorine ... Which is a function of the CYA level. See the chart in Pool School.

    This is not a consensus just here ... It is a chemistry fact.
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    Re: Have your water checked for phosphates and nitrates

    The consensus here at TFP is that if the FC to CYA ratio is maintained properly, then no growth of algae will occur.

    CYA buffers FC effectiveness. 7ppm of FC is useless if you have CYA of +100.

    If the FC is 11.5% of the CYA, then it is sufficient to prevent the growth of algae regardless of the phosphate and nutrient level.

    This is what almost all of the "pool pros" do not understand.





    Quote Originally Posted by williamsonpools View Post
    So the consensus around here is that the presence of high nitrates does NOT Cause rapid algae growth
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    Re: Have your water checked for phosphates and nitrates

    Quote Originally Posted by williamsonpools View Post
    Nitrates and nitrites are products of nitrogen gas. Nitrate which consist of a single nitrogen atom connected to 3 oxygen atoms(No3) is extremely stable or hard to remove. Nitrogen (No2) can enter your pool water from a variety of sources. It combines with oxygen to form nitrites (No2). This extra oxygen atom is not just floating on top of your pool (unless using an ozinator) so the aggressive nitrogen oxide will steal another o atom from our chlorine molecule HOCL. This makes our chlorine less effective and increases your chlorine demand. This continues as nitrites take to another oxygen atom to become nitrates (No3)
    Nitrates and nitrites in pools are NOT products of nitrogen gas. I think you are mixing up pools with what goes on in soil with nitrogen-fixing bacteria that convert nitrogen gas in the atmosphere into ammonia followed by nitrifying bacteria that further convert it to nitrite and nitrate that is used as a source of nitrogen for such bacteria and by plants (interestingly the plants reduce nitrate to nitrite to ammonia for chemical reactions that incorporate nitrogen into nitrogenous organics).

    The source of nitrates in pools is from the chlorine oxidation of ammonia and nitrogenous organics. While most of the nitrogen in ammonia becomes nitrogen gas when chlorine oxidizes it, around 15% becomes nitrate (the actual amount depends on relative concentrations of chlorine and ammonia).

    Both phosphates and nitrates are essential nutrients required for plant growth including algae which are plants (even bacteria need phosphates and nitrates, but in lower quantities since they are smaller; by the way, black algae is technically a cyanobacteria). These are essential nutrients to all living things because the phosphorous is used in the core chemical energy system ADP/ATP and in the phosphate deoxyribose backbone of both DNA and RNA while nitrogen is found in many organic compounds including amino acids (and therefore proteins), DNA, RNA and many other compounds.

    However, just because phosphates and nitrates are essential nutrients for algae does NOT mean that algae will always grow faster than chlorine can kill it. There is a limit to the rate at which algae can grow regardless of the phosphate or nitrate level. Algae is also limited in its growth by the amount of sunlight and by temperature. So if one has a sufficiently high active chlorine (hypochlorous acid) level, then algae will be killed faster than it can grow regardless of algae nutrient (phosphate and nitrate) level.

    The problem is that you were probably never told how to figure out the active chlorine (hypochlorous acid) level that is required to kill algae faster than it can grow. The Free Chlorine (FC) to Cyanuric Acid (CYA) ratio determines that active chlorine level. So long as this FC/CYA ratio is 7.5% or larger in non-SWG pools, then green and black algae will be killed faster than they can grow. This assumes, of course, that you don't already have an algae bloom. If you do, then it takes higher levels of chlorine to kill the algae because 1) the chlorine gets consumed quickly oxidizing the algae and 2) the algae in a bloom is clumped so the algae inside the clumps can still grow so it takes higher levels of chlorine to get inside those clumps more quickly to kill the algae.

    Think of phosphates and nitrates being fuel for a fire, so like wood in a fireplace. If you try to start a flame (algae growth) but are dousing the wood with water (chlorine) fast enough to put out the flame, then it doesn't matter how much wood there is in the fireplace. A fire will simply not get started because you are putting it out faster. The amount of fuel is irrelevant. You just have to remember that the FC number by itself does NOT represent the strength of the chlorine. It only represents the capacity or reservoir of chlorine. The activity of the chlorine is proportional to the FC/CYA ratio. So if you have higher CYA, then you need a higher FC level to maintain the same chlorine activity. If you don't do that, then algae can grow faster than chlorine can kill it.
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    Re: Have your water checked for phosphates and nitrates

    What I am confused about is how you can maintain proper FC to CYA ratio when free chlorine is removed quickly from the chemical reaction from nitrites

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    Re: Have your water checked for phosphates and nitrates

    There is NO chemical reaction between chlorine and nitrates nor between chlorine and phosphates. What chemical reaction do you believe is occurring?

    Chlorine is an oxidizer and the nitrogen in nitrates is completely oxidized -- it can only get reduced, not oxidized (see this link where the +5 oxidation state for nitrogen, as found in nitrate, is the highest so neither chlorine nor any other oxidizer can oxidize it further).

    As for phosphates, the phosphorous is fully oxidized as well at the +5 oxidation state (see this link) so again neither chlorine nor any other oxidizer can oxidize it further.
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    Re: Have your water checked for phosphates and nitrates

    I said nitrites not nitrates

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    Re: Have your water checked for phosphates and nitrates

    Yes, chlorine will oxidize nitrite to nitrate, but where will that nitrite be coming from? In a pool with chlorine you only find nitrates precisely because nitrite gets oxidized to nitrate from chlorine. The oxidation of ammonia and organics produces nitrate. There is no leftover nitrite from that. What is the source of nitrites for the pool? There is none.

    When you had your problem pools, you didn't test for nitrite, did you? You tested for nitrate and maybe for phosphate. Those are algae nutrients but chlorine does not react with them. You wrote earlier about nitrates, not nitrites (bold emphasis in your quotes is mine):

    Quote Originally Posted by williamsonpools View Post
    True only way to lower cya is to drain and add fresh water have your water checked for phosphates and nitrates they eat up chlorine
    Quote Originally Posted by williamsonpools View Post
    All I am saying last year working in maryland I had a couple of POOLs that turned green overnight and we could not get them to come back around we found high nitrates in the pool we drained water and refilled which lowered nitrates in the pool problem solved we came to the conclusion it was caused by a fertilizer the lawn people using
    I had over 3000 ppb phosphates in my pool and had nitrates as well and the pool was very "reactive" in that chlorine demand would rise and the pool would get dull to cloudy if I let the FC/CYA ratio get too low, but so long as I kept the FC/CYA ratio where it is supposed to be then the chlorine demand was normal and the water crystal clear (see this photo and yes, there is water in the pool).
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    Re: Have your water checked for phosphates and nitrates

    The fire wood analogy is the best simple explanation of this, and I repeat it all the time.

    It does not matter if there is food for the Algae to eat if it is DEAD. Algae simply cannot live where there is an adequate amount of Free Chorine. It really does boil down to this very simple fact. I encourage you to stick around williamson, there is no magic in what we teach. It's all about the most basic and fundamental things.

    Proper pH, proper FC/Cya ratio, prudent and proper testing, then responding accordingly with understanding of the basics. Pool care really isn't more difficult than that. There are lots of myths, and misnomers about pools out there, and we simply overcome them with the basic facts of the fundamentals.
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    Re: Have your water checked for phosphates and nitrates

    chem geek I get what your saying in fact I guess a pool with nitrates it's not the problem it's the process of how the hight level of nitrates came to be ( nitrites oxidizing into nitrates) this causing are Fc to cya ratio to be off causing pool to become green so in the end what needed to be done was dilution which lowered the nitrates at the same time lowering cya

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