I AM HAVING AN UNUSAL CASE OF PEOPLE WITH CHLORINE DEMAND!!! i HAVE CUSTOMERS WHO ARE SHOCKING THE BEEGEEBEESS OUT OF THEIR POOLS AND THEY ARE STILL NOT GETTING A CHLORINE READING WITHIN ONE OR TWO DAYS I HAVE CHECKED FOR STABILIZER AND MADE SURE ALL OTHER CHEMICALS ARE IN THE RITE RANGE AND THEY STILL SEEM TO CONSUME CHLORINE! i THAWT MAYBE PHOSPHATES BUT STILL NO HELP.......PLEASE GIVE ANY ADVISE YOU MAY SEEM SUITABLE...ALSO ANYONE THAT CAN HELP ME UNDERSTAND HOW NON-CHLORINE SHOCK WILL HELP IN THIS INSTANCE!!!! THANXS
I need to amend what I wrote when I said "I am not saying that phosphates aren't bad (in terms of allowing for algae growth) nor that phosphate removers don't work." I should have said "...nor that phosphate removers don't usually work". There have been enough reports of pool owners using phosphate removers properly that still get algae growth that I cannot say it always works. The reason may be that though phosphate removers remove orthophosphate, they do not remove organic phosphates and algae can still utilize small organic phosphates for growth, though the absorption rate is much slower.
This does not change the main point which is that one can keep a pool algae free by properly maintaining the Free Chlorine (FC) level relative to the Cyanuric Acid (CYA) level in spite of high phosphate and nitrate levels.
Have you checked these pools for Nitrates? Also is the chlorine demand depleting all of the chlorine or just the FAC? An increase in chlorine consumption can easily be caused by an increase in the pool waters temperature! If your customers are getting a greater demand but no increase the output of their chlorinator or generators they will not get a reading.
If they are being depleted on the FAC and not on the total chlorine shocking will not help unless you are reaching break point chlorination. I would recommend checking the chlorine with a long range kit. I have had cases where the cac has gotten so high that it bleaches the reagents giving a false reading (ie a zero reading).
If this is not the case check the nitrate concentration. If you have a nitrate level partially drain the pool and that should alleviate the problem. In some cases shocking has gotten rid of nitrates but is more costly than draining.
To put things into perspective in terms of higher FC levels, when a pool has an FC that is roughly 10% of the CYA level, this is technically equivalent in terms of active chlorine (hypochlorous acid) to a pool with an FC of around 0.1 ppm with no CYA. Yes, you read that correctly -- CYA lowers chlorine activity by that large amount. In the scenario I just described, around 97% of the chlorine is bound to CYA is is not a strong oxidizer nor disinfectant (this post has references to scientific literature on this). Considering that most indoor pools do not use CYA and have at least 1 ppm FC, they have over 10 times the active chlorine concentration and oxidize swimsuits, skin and hair at roughly 10 times the rate (and produce nitrogen trichloride at roughly 10 times the rate as well, according to theory -- no one has tested this yet).
So swimming in water with 3 ppm FC and 30 ppm CYA is the same as water with 10 ppm FC and 100 ppm CYA, etc. It's obviously different if you were to drink the pool water since in that case it's the total chlorine in what you drink that would be relevant, but people don't drink pool water (even accidentally) on a daily basis.
I am not saying that phosphates aren't bad (in terms of allowing for algae growth) nor that phosphate removers don't work. What I am saying is that they are unnecessary if you maintain an appropriate Free Chlorine (FC) level relative to the Cyanuric Acid (CYA) level. There is absolutely nothing wrong with using a phosphate remover if you want to, but they aren't free and they have side effects. If used properly (i.e. to lower the phosphate level low enough) then it will prevent algae from growing. Then again, so will a copper-based algaecide. There is no one single solution and each of these has side effects.
For phosphate removers, if you aren't reintroducing phosphates regularly into the pool then a single, usually large and expensive dose, will remove the phosphates and with small maintenance doses you'll be in good shape. However, if your fill water has phosphates or you regularly get blown-in fertilized soil, then you'll need to add more phosphate remover regularly which is both costly and can cause temporary cloudiness or require vacuum-to-waste (depending on the amount of precipitated phosphate).
It's orthophosphate that is what algae primarily use as a nutrient. However, if you use the better metal sequestrants, these have HEDP which are slowly broken down by chlorine and produce orthophosphate. There are weaker metal sequestrants based on EDTA, but these break down even more quickly by chlorine though they do not produce phosphates.
Borates are a weak algaecide -- not as strong as copper nor as limiting as removing phosphates (below 125 ppb). They help, but are not a solution. However, managing an appropriate FC relative to CYA does prevent green algae growth.
Bruce, you mention that you couldn't operate your pools at a 3 ppm FC level, but that level is too low if your CYA level is above around 40 ppm or so (certainly above 60 ppm you'll have problems if there are algae nutrients and no algaecide). Even the saltwater chlorine generator manufacturers recommendations of 1-3 ppm with 60-80 ppm CYA are insufficient. At 80 ppm CYA, one needs the FC to be at least 3.6 ppm (4 ppm is safer) to prevent green algae growth. So there is more than one way to stop the algae from growing -- maintain a sufficient FC relative to CYA OR use an algaecide or phosphate remover.
Even if you use a phosphate remover or algaecide, this only takes care of the algae growth, but does not change a high CYA level making chlorine less effective for oxidation (in addition to sanitation, but that's not normally an issue for most pathogen). So you end up having to shock the pool to get ahead of this situation of slower oxidation of bather waste. If you just maintained the appropriate FC relative to CYA, you would not only get algae prevention, but would hardly ever need to shock the pool.
The other thing I personally don't like about the phosphate remover approach is that there are no inexpensive test kits for testing the phosphate level accurately as must be done to ensure that the level is below 125 ppb. This prevents pool owners from properly managing their pools. Taylor does make the K-1106 but it's not as easy to use as drop-based tests for TA, CH, FAS-DPD chlorine, etc.
Again, I'm not promoting one approach over the other, but want to make sure it is understood that the reason for algae growth in most pools is that the FC/CYA relationship is not understood (nor taught). It has been known science since at least 1974 (as described in [url=http://richardfalk.home.comcast.net/~richardfalk/pool/OBrien.htm]this paper[/url]) but is not taught in NSPF CPO nor ANSI TECH courses -- even the chemical facts I gave aren't taught in such courses.
Richard,
Thankyou for sharing your insight and look forward to reading your responses. My offerings are based on purely anecdotal evidence and rely on those such as yourself to help me find solutions.
Many fine scientists and engineers work very hard to discover and solve water mysteries andin the last 15 yrs. there has been a lot of focus on phosphates. When trying to solve my own water related troubles, we focused on the usual supects, pH, TDS, FC, algicides, CYA, all with some success. We next treated 300+ pools with borates. Again some sucess. A small percentage of our pools had high nitrare levels, and after drain and refill,again had marked improvement. Still though, our pools were troublsome and required using more chlorine than I was accustomed to in other locals. There was 1.9 ppm phosphate in the supply water.
A prominent mfgr. did some phosphate removal research at our private location and this was what finally enabled our pools to operate at 3ppm with infrequent shocking.
Are there different forms of phoshate that are problematic and others that are not?
Can harmless forms of phosphate "morph" into problematic forms?
Why does phosphate removal enjoy such popularity and apparent success?
Phosphates do not consume chlorine. There is no chemical reaction between them (not even catalysis). Phosphates are one of the essential nutrients algae needs to grow (another being nitrates and some form of carbon as with carbonates or carbon dioxide plus sunlight). You need to look at a phosphate remover the same way you look at algicides.
I have 2000-3000 ppb phosphates in my 16,000 gallon pool (shown here) and others have as much as 5000 ppb and do NOT get algae because we maintain an appropriate Free Chlorine (FC) level relative to the Cyanuric Acid (CYA) level in our pools. I have 300-500 ppb phophates in my fill water that the municipal water district adds for corrosion control and I have blown-in fertilized soil on occassion. Algae can only grow so fast given limits on temperature and sunlight so after some level of nitrates and phosphates any higher amount doesn't matter. One needs to have enough active chlorine (hypochlorous acid) in the water in order to kill algae faster than it can grow, even under these "ideal" conditions that have lots of algal nutrients.
The amount of active chlorine in the water when CYA is present has nothing to do with the FC level alone. It is proportional to the FC/CYA ratio (technical derivation of this is here and you can see the true graph of active chlorine vs. pH without and with CYA here). Most pools that have algae problems have an FC level that is too low relative to the CYA level. This usually occur due to continued use of stabilized chlorine products. The following are chemical rules of fact that are independent of concentration of product and of pool size:
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by 7 ppm.
So even with a low 1 ppm FC per day chlorine usage, after 6 months of Trichlor usage the CYA increases by over 100 ppm unless there is significant water dilution. Unless the FC is proportionately increased with the rising CYA level, then algae can grow (if there are sufficient nutrients). It is hard to maintain higher FC using Trichlor alone since the pucks don't dissolve that quickly. If one uses chlorinating liquid (or 6% unscented bleach) as their primary source of chlorine, then they get neither a buildup of CYA nor CH though the salt level increases twice as fast as with the other sources of chlorine (though that's not a big deal since salt levels are much more innocuous than CYA and CH until they get rather high and are much easier to dilute proportionately). By the way, regular use of hypochlorite sources of chlorine does not make the pH rise over time because the consumption/usage of chlorine is acidic and compensates for the initial rise in pH from chlorine addition (technical details about this are here).
If you have a seemingly insatiable chlorine demand yet the water is clear, then you may have ammonia in the water. This can occur of the FC level gets to zero at which point bacteria can convert CYA into ammonia (technical details about this are here including how it happened in my own pool when I stupidly let the chlorine too low here). As noted in the referenced post, one can use an inexpensive ammonia test kit to roughly determine how much cumulative FC it will take to clear the chlorine, though a bucket test is better since some intermediate compounds won't show up in the ammonia test yet still need to get oxidized by chlorine.
The comment about the 10x rule and breakpoint with chlorine is incorrect because the 10x rule is relative to ammonia, not Combined Chlorine (CC), but I don't have time to get into details of that here right now. There is no "getting stuck" if you don't add enough chlorine. You can just add more until you fully oxidize ammonia and it intermediate chloramine products. There are issues with creating more irritating and volatile nitrogen trichloride if you don't have any CYA in the water (as with most indoor pools -- something I believe is wrong) and this is described technically here.
As for how much chlorine is needed in a pool to prevent green algae, for manually dosed pools this is an FC that is a minimum of around 7.5% of the CYA level. For saltwater chlorine generator (SWG) pools, it is a minimum FC that is around 4.5% of the CYA level. The shock level to relatively quickly kill and oxidize existing algae (even if it is nascent and not quite visible) is an FC that is around 40% of the CYA level though anything above around 20% of the CYA level will kill it faster than it grows but will take longer to kill. Yellow/Mustard algae requires higher levels -- shock is around an FC that is 60% of the CYA level. As you can tell, it becomes impractical to shock pools that have a very high CYA in them which is why you see products that "work around" the CYA issue such as sodium bromide that produce bromine that does not bind to CYA and ammonium products that produce monochloramine that likewise does not bind to CYA, but these products produce additional chlorine demand after their use (for a while).
Finally, if one maintains the proper FC/CYA ratio as indicated above, then one rarely needs to shock a pool, at least in a residential low-to-medium bather load environment. In a commercial/public pool with high bather load, the amount of organic and ammonia buildup may be such that periodic shocking helps to accelerate such oxidation, especially if there is not supplemental oxidation from an ozonator (or UV system, to some small extent).
If one wants to have some sort of persistent algicide that doesn't require weekly dosing and has minimal side effects, then one can use 50 ppm Borates in their pools (e.g. Proteam Supreme Plus, or boric acid, or a combination of 20 Mule Team Borax with Muriatic Acid added separately or course). Copper-based algicide is persistent, but can stain pool surfaces and turn blond hair greenish, etc. PolyQuat 60 is a good algicide but requires weekly addition since it slowly breaks down from chlorine (inexpensive linear quat algicides are not quite as effective and can foam).
Comments
This does not change the main point which is that one can keep a pool algae free by properly maintaining the Free Chlorine (FC) level relative to the Cyanuric Acid (CYA) level in spite of high phosphate and nitrate levels.
If they are being depleted on the FAC and not on the total chlorine shocking will not help unless you are reaching break point chlorination. I would recommend checking the chlorine with a long range kit. I have had cases where the cac has gotten so high that it bleaches the reagents giving a false reading (ie a zero reading).
If this is not the case check the nitrate concentration. If you have a nitrate level partially drain the pool and that should alleviate the problem. In some cases shocking has gotten rid of nitrates but is more costly than draining.
So swimming in water with 3 ppm FC and 30 ppm CYA is the same as water with 10 ppm FC and 100 ppm CYA, etc. It's obviously different if you were to drink the pool water since in that case it's the total chlorine in what you drink that would be relevant, but people don't drink pool water (even accidentally) on a daily basis.
For phosphate removers, if you aren't reintroducing phosphates regularly into the pool then a single, usually large and expensive dose, will remove the phosphates and with small maintenance doses you'll be in good shape. However, if your fill water has phosphates or you regularly get blown-in fertilized soil, then you'll need to add more phosphate remover regularly which is both costly and can cause temporary cloudiness or require vacuum-to-waste (depending on the amount of precipitated phosphate).
It's orthophosphate that is what algae primarily use as a nutrient. However, if you use the better metal sequestrants, these have HEDP which are slowly broken down by chlorine and produce orthophosphate. There are weaker metal sequestrants based on EDTA, but these break down even more quickly by chlorine though they do not produce phosphates.
Borates are a weak algaecide -- not as strong as copper nor as limiting as removing phosphates (below 125 ppb). They help, but are not a solution. However, managing an appropriate FC relative to CYA does prevent green algae growth.
Bruce, you mention that you couldn't operate your pools at a 3 ppm FC level, but that level is too low if your CYA level is above around 40 ppm or so (certainly above 60 ppm you'll have problems if there are algae nutrients and no algaecide). Even the saltwater chlorine generator manufacturers recommendations of 1-3 ppm with 60-80 ppm CYA are insufficient. At 80 ppm CYA, one needs the FC to be at least 3.6 ppm (4 ppm is safer) to prevent green algae growth. So there is more than one way to stop the algae from growing -- maintain a sufficient FC relative to CYA OR use an algaecide or phosphate remover.
Even if you use a phosphate remover or algaecide, this only takes care of the algae growth, but does not change a high CYA level making chlorine less effective for oxidation (in addition to sanitation, but that's not normally an issue for most pathogen). So you end up having to shock the pool to get ahead of this situation of slower oxidation of bather waste. If you just maintained the appropriate FC relative to CYA, you would not only get algae prevention, but would hardly ever need to shock the pool.
The other thing I personally don't like about the phosphate remover approach is that there are no inexpensive test kits for testing the phosphate level accurately as must be done to ensure that the level is below 125 ppb. This prevents pool owners from properly managing their pools. Taylor does make the K-1106 but it's not as easy to use as drop-based tests for TA, CH, FAS-DPD chlorine, etc.
Again, I'm not promoting one approach over the other, but want to make sure it is understood that the reason for algae growth in most pools is that the FC/CYA relationship is not understood (nor taught). It has been known science since at least 1974 (as described in [url=http://richardfalk.home.comcast.net/~richardfalk/pool/OBrien.htm]this paper[/url]) but is not taught in NSPF CPO nor ANSI TECH courses -- even the chemical facts I gave aren't taught in such courses.
Richard
After rereading your comment, I believe you've already answered my questions.
Thankyou for sharing your insight and look forward to reading your responses. My offerings are based on purely anecdotal evidence and rely on those such as yourself to help me find solutions.
Many fine scientists and engineers work very hard to discover and solve water mysteries andin the last 15 yrs. there has been a lot of focus on phosphates. When trying to solve my own water related troubles, we focused on the usual supects, pH, TDS, FC, algicides, CYA, all with some success. We next treated 300+ pools with borates. Again some sucess. A small percentage of our pools had high nitrare levels, and after drain and refill,again had marked improvement. Still though, our pools were troublsome and required using more chlorine than I was accustomed to in other locals. There was 1.9 ppm phosphate in the supply water.
A prominent mfgr. did some phosphate removal research at our private location and this was what finally enabled our pools to operate at 3ppm with infrequent shocking.
Are there different forms of phoshate that are problematic and others that are not?
Can harmless forms of phosphate "morph" into problematic forms?
Why does phosphate removal enjoy such popularity and apparent success?
I have 2000-3000 ppb phosphates in my 16,000 gallon pool (shown here) and others have as much as 5000 ppb and do NOT get algae because we maintain an appropriate Free Chlorine (FC) level relative to the Cyanuric Acid (CYA) level in our pools. I have 300-500 ppb phophates in my fill water that the municipal water district adds for corrosion control and I have blown-in fertilized soil on occassion. Algae can only grow so fast given limits on temperature and sunlight so after some level of nitrates and phosphates any higher amount doesn't matter. One needs to have enough active chlorine (hypochlorous acid) in the water in order to kill algae faster than it can grow, even under these "ideal" conditions that have lots of algal nutrients.
The amount of active chlorine in the water when CYA is present has nothing to do with the FC level alone. It is proportional to the FC/CYA ratio (technical derivation of this is here and you can see the true graph of active chlorine vs. pH without and with CYA here). Most pools that have algae problems have an FC level that is too low relative to the CYA level. This usually occur due to continued use of stabilized chlorine products. The following are chemical rules of fact that are independent of concentration of product and of pool size:
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by 7 ppm.
So even with a low 1 ppm FC per day chlorine usage, after 6 months of Trichlor usage the CYA increases by over 100 ppm unless there is significant water dilution. Unless the FC is proportionately increased with the rising CYA level, then algae can grow (if there are sufficient nutrients). It is hard to maintain higher FC using Trichlor alone since the pucks don't dissolve that quickly. If one uses chlorinating liquid (or 6% unscented bleach) as their primary source of chlorine, then they get neither a buildup of CYA nor CH though the salt level increases twice as fast as with the other sources of chlorine (though that's not a big deal since salt levels are much more innocuous than CYA and CH until they get rather high and are much easier to dilute proportionately). By the way, regular use of hypochlorite sources of chlorine does not make the pH rise over time because the consumption/usage of chlorine is acidic and compensates for the initial rise in pH from chlorine addition (technical details about this are here).
If you have a seemingly insatiable chlorine demand yet the water is clear, then you may have ammonia in the water. This can occur of the FC level gets to zero at which point bacteria can convert CYA into ammonia (technical details about this are here including how it happened in my own pool when I stupidly let the chlorine too low here). As noted in the referenced post, one can use an inexpensive ammonia test kit to roughly determine how much cumulative FC it will take to clear the chlorine, though a bucket test is better since some intermediate compounds won't show up in the ammonia test yet still need to get oxidized by chlorine.
The comment about the 10x rule and breakpoint with chlorine is incorrect because the 10x rule is relative to ammonia, not Combined Chlorine (CC), but I don't have time to get into details of that here right now. There is no "getting stuck" if you don't add enough chlorine. You can just add more until you fully oxidize ammonia and it intermediate chloramine products. There are issues with creating more irritating and volatile nitrogen trichloride if you don't have any CYA in the water (as with most indoor pools -- something I believe is wrong) and this is described technically here.
As for how much chlorine is needed in a pool to prevent green algae, for manually dosed pools this is an FC that is a minimum of around 7.5% of the CYA level. For saltwater chlorine generator (SWG) pools, it is a minimum FC that is around 4.5% of the CYA level. The shock level to relatively quickly kill and oxidize existing algae (even if it is nascent and not quite visible) is an FC that is around 40% of the CYA level though anything above around 20% of the CYA level will kill it faster than it grows but will take longer to kill. Yellow/Mustard algae requires higher levels -- shock is around an FC that is 60% of the CYA level. As you can tell, it becomes impractical to shock pools that have a very high CYA in them which is why you see products that "work around" the CYA issue such as sodium bromide that produce bromine that does not bind to CYA and ammonium products that produce monochloramine that likewise does not bind to CYA, but these products produce additional chlorine demand after their use (for a while).
Finally, if one maintains the proper FC/CYA ratio as indicated above, then one rarely needs to shock a pool, at least in a residential low-to-medium bather load environment. In a commercial/public pool with high bather load, the amount of organic and ammonia buildup may be such that periodic shocking helps to accelerate such oxidation, especially if there is not supplemental oxidation from an ozonator (or UV system, to some small extent).
If one wants to have some sort of persistent algicide that doesn't require weekly dosing and has minimal side effects, then one can use 50 ppm Borates in their pools (e.g. Proteam Supreme Plus, or boric acid, or a combination of 20 Mule Team Borax with Muriatic Acid added separately or course). Copper-based algicide is persistent, but can stain pool surfaces and turn blond hair greenish, etc. PolyQuat 60 is a good algicide but requires weekly addition since it slowly breaks down from chlorine (inexpensive linear quat algicides are not quite as effective and can foam).
Richard
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