Phosphates.....are they worth removing??

[AUSpool]

I guess I can try. It's something I immediately thought of when I first looked at this thread and I should add that I was or am a late arrival. I have never winterised a pool and haven't read about the process but I have read a few accounts now where the cover is pulled back to reveil a green mess. I was thinking that it could be like a bit of an insurance policy, could help but there's no guarantee. And back not that far it was reported that a phosphate removal item was included in a winterising kit so I guess I'm not the first to think of it in that regard. But again there are are no guarantees and adding an algacide could just as effective but it would depend on what is in each product and how much water an individual can afford to waiste on backwashing and or dilution etc.

 

[Swampwoman]

^i do feel like I'm playing roulette during winter closing. I am nervous about opening this year and am moving it up two weeks due to abnormally warmer temps and fluctuations.

But I can say that with 25,000 ppb phosphates the last two seasons, I've opened with a residual FC of 3-4 ppm without polyquat and without algae. If I didn't open cold, I'm pretty sure that would be another story

As ChemGeek pointed out in past posts, though, algae reproduction is still limited by sunlight etc., so how ever much food there is, it can only multiply at a given, limited rate regardless. Eg. It can't eat the whole thing So while high po4 might make you more reactive to onset in low FC, it doesn't necessarily accelerate/increase growth rate or magnitude, which is limited by environmental factors.

Which is kind of another argument against focusing on po4 in relation to algae. I'm leaning towards thinking about po4 more in terms of equipment, like swg and heaters...

 

[klynch494]

I am with you swampwoman... I closed and opened cold this year without the use of an algaecide in the fall and have had no issues. Who knows, I may do it again this year. My water temp has ran anywhere between 44 and 52 degrees so far (gotta love the north country).

Call it being a new pool owner as of this past summer and maybe a little naive, but I was just unsure of adding the algicide as I didn't dig deep enough into the forum last year to know any better. I had the BBB method ingrained in my brain and was like, "I ain't adding nothing else into my pool and ruining my clear water." The only thing I did do to winterize was hyper chlorinate a little bit.

~Kevin (MN)
13.5k gal, 24' Round AG Vinyl
2HP Waterway Pump, 200sqft Hayward Element Filter
BBB Method & AuquaSmarte Inline Chlorinator, TF-100 Test Kit

 

[duraleigh]

It seems clear that a high level of phosphate can adversely affect equipment.....

Well, that is new, I think. What equipment does phosphates affect?

 

[Swampwoman]

^upthread, Dave, are some links to two Aqua magazine articles discussing potential phosphate scaling of heaters and swg cells.
In one, the mystery phosphate heater scaling was identified by a member of the onBalance team, so I trust the testing The other article discusses the potential impact on SWG but makes clear this is new territory without defined guidelines. Since I am about to purchase an Aquarite system, I will submit a query to see what they say

From od threads and conversations between smallpooldad and ChemGeek, plus me and ChemGeek last year, there is also a formula to attempt to predict possible levels for phosphate scaling, which are dependent on calcium, ph and temp.

 

[AUSpool]

I wouldn't include light as a limiting factor in a pool, cold yes, light no. Planktonic algae will survive all the way to the compensation level were at just 1% of full sunlight photosynthetic activity balances respiratory activity. I read a short passage yesterday that stated that high phosphate levels can limit growth to, with no explanation it's interesting but I wouldn't go there.

My text book appears to include phosphate and nitrate together when talking about limiting nutrients. Growth rates increase with increasing molar concentrations of both phosphates and nitrates then decline as the molar concentration of phosphate is maintained at 0.0007(M) and the concentration of nitrate is decreased. Sorry, my chemistry is to rusty to covert the molar concentration to ppb.

I'm not sure but I was thinking that treating with lanthanum chloride my reduce nitrates as well but I'm not sure.

 

[JoyfulNoise]

I'm not sure but I was thinking that treating with lanthanum chloride my reduce nitrates as well but I'm not sure.

Unlike phosphates, almost all inorganic nitrate salts are soluble in water at STP. Lanthanum phosphate is insoluble in water while lanthanum nitrate is very soluble in water.

 

[Swampwoman]

I know there's a more detailed explanation somewhere burried in a thread, but I was referring to this kind of previous statement from one of our more versed past posters:

The thing is that providing all the food in the world for algae will not make them grow any faster than their limit due to sunlight and temperature and that's roughly doubling in 3-8 hours

 

[AUSpool]

Thanks Matt, I wasn't sure but knew you would know.

When it comes to nutrients the data I have appears to support that, that an excess of the minimum requirement will provide no more effect on growth rates as long as the minimum is maintained. If nutrients are deficient growth rate will decline but the population density will remain the same. If and adiquite level of nutrient is maintained growth will continue. When any one factor becomes limiting growth will enter what in micro terms is called the stationary phase which can continue for a long time and while other factors become limiting. I don't know if it means much but my Microbiology book, Brock, Biology of Microbiology, deals with carbon and Nitrogen together and lumps phosphate in with all the other, P, S, K, Mg, Ca, Na and Fe. If I get a chance I'll add more data to the limiting effect of phosphorus and nitrogen.

In regards to light when I first read within the forum that it is limiting on growth I was a little unsure but didn't know why. There are plenty of stories hear where the covers are pulled back to reveal an algae bloom which indicates that there is enough light getting through a cover to provide for substantial growth. I realise that what I said before goes against the general wisdom hear but what I wrote before was almost a direct recital from Atlas and Bartha, Microbial Ecology, and I have no doubt to question a universities set text. A bed time story from a microbial biology or ecology text book. Looking back on this text after a while with it sitting on the shelf the section I've been looking in has a lot of limnology in it.

 

[JoyfulNoise]

I think what is important to keep in mind here is that residential pools are not stagnant lakes, or rivers or oceans. A residential swimming pool is a body of water that has a VERY large concentration of disinfectant in (at least from a microbiological point of view). Therefore, life cycles are not really as important as reproduction rates because the chlorine in the water is continuously killing algae as it grows. The most basic way to describe this phenomenon is that, in order to keep a pool clear, the kill rate from chlorine (which is concentration dependent) MUST EXCEED the reproduction rate of the pathogen. If the sanitizer levels drop, then algae reproduction rates will exceed their extinction rates and algae will start to bloom. This can even happen when there is still a measurable amount of chlorine in the water because pools are not very well mixed and there can be areas within the water column where the chlorine is very low or even non-existent.

So, in gross terms, the FC/CYA ratio concerns itself with the first part of the equation - sanitizer kill rates. The higher the FC/CYA ratio, the greater the concentration of hypochlorous acid and the faster the kill rates.

What the discussion in this thread is about is the OTHER SIDE of the equation. Can we do "something" to the water to reduce or restrict algae growth rates. If the answer is that we can MEANINGFULLY affect those growth rates (inhibit them), then the balance of the equation changes and we can use less sanitizer.

Where that balance lies and if phosphate removers can have meaningful and measurable impact is what we are after.

 

[AUSpool]

Thanks Matt, I get what your saying about the front side of the FC/CYA ratio in regards to sanitation and for what is worth I don't think I've said anything new, just maybe added a bit of clarity if only for myself.

I'm not really sure where your going with the idea of reducing the reducing the FC/CYA ratio though. At the curent levels there is no bather health risks. For me with my SWG there is no financial gain. I can see that there would be financial gain if using bleach but how much and would it be enough to offset an increase in nutrient monitoring? Is it worth pushing the envelope. It's hard to monitor nutrient fluctuations, I'd be wary evey time there's a storm, when I add top up water or have an increase in bather load. I think it would be more than just limiting phosphate which is I bit of a task for some, but I think nitrates should be limited also or at lest addressed. I must have missed it but why whould we want to lower the FC/CYA ratio?

 

[MarianParoo]

I love that TFP is having this discussion, BTW.

Steve: for me, with my non-SWG pool, I raise my FC/CYA ratio for high bather load anyway, and test after, and even mid-party, then adjust appropriately. Having a lower ratio would not affect that procedure. It's the ratio that matters.

Topping off and rain don't affect my numbers significantly. I not only know my pool's habits, but I also have an auto-cover which reduces evaporation and helps control the amount of rainwater that mixes with the water.

 

[JoyfulNoise]

Thanks Matt, I get what your saying about the front side of the FC/CYA ratio in regards to sanitation and for what is worth I don't think I've said anything new, just maybe added a bit of clarity if only for myself.

I'm not really sure where your going with the idea of reducing the reducing the FC/CYA ratio though. At the curent levels there is no bather health risks. For me with my SWG there is no financial gain. I can see that there would be financial gain if using bleach but how much and would it be enough to offset an increase in nutrient monitoring? Is it worth pushing the envelope. It's hard to monitor nutrient fluctuations, I'd be wary evey time there's a storm, when I add top up water or have an increase in bather load. I think it would be more than just limiting phosphate which is I bit of a task for some, but I think nitrates should be limited also or at lest addressed. I must have missed it but why whould we want to lower the FC/CYA ratio?

Steve,

In case you missed it, here's the concept in a nutshell - by utilizing phosphate control, some people have reported cutting their FC/CYA ratio in half and having pool water that is much less reactive to algae (i.e., algae may get introduced, but it is very slow to bloom). Here's an example of HOW the math MIGHT work out IF a 50% reduction in the FC/CYA ratio is possible -

Scenario #1 : Standard TFP Bleach User (7.5% FC/CYA ratio)

CYA.......Min FC.....FC Loss per day
50............4............2-3

So, in order to stay above the minimum FC needed, one needs to dose a pool between 6 (=4+2) and 7 (=4+3) ppm of FC per day to comply with the 7.5% FC/CYA ratio.

Scenario #2 : Phosphates removed and assuming one can use a 3.75% FC/CYA Ratio

CYA.......Min FC.....FC Loss per day
50............2............1-1.5

So, in order to stay above the minimum FC needed, one needs to dose a pool between 3 (=2+1) and 3.5 (=2+1.5) ppm of FC per day to comply with the 3.75% FC/CYA ratio.

The loss rate is proportional to the FC/CYA ratio because at a higher FC/CYA ratio (for example, SLAM is a 40% FC/CYA) you lose more total chlorine (FC) per hour since the amount of active chlorine (hypochlorous acid and hypochlorite) in the water is larger. In both of the cases above, the fractional amount of chlorine lost per day is the same (1/3rd loss). The presumed benefit of phosphate removal is that it allows you to cut the FC/CYA ratio in half therefore you use half as much chlorine any time you add your maintenance dose to get the pool to an FC level where it will stay above the minimum (some people add chlorine every day others every other day or so).

As I have said over and over again, the FC/CYA ratio is not some hard & fast rule that is rigorously derived from first-principles. It's a statistical quantity that was observed mostly from experience and then given some scientific under-pinning through use of microbiological data on the sanitizing effects of chlorine. If you want evidence that it is not "written in stone" you have to look no further than TFP's own recommendations for SWG users. For SWG pools, the FC/CYA ratio is 5% whereas it is 7.5% for manually-dosed bleach pools. Why? I mean, it's not like SWGs are magical or anything....we always say that a salt water pool is a bleach pool...but yet, we allow for a much lower level of chlorine to be used based on the experience of SWG owners that show they can operate a pool at a 5% ratio with a higher stabilizer (CYA) level...

So, at the end of the day, the burden of proof is on folks like me that choose to experiment. As I said in a previous post, I will keep copious notes and respond back and let you all know how the swim season went. I have "no dog in this fight", I am simply motivated by curiosity. Hopefully I don't generate a green swamp but, if I do, it can easily be fixed and I'll post plenty of pictures of it so you all can make fun of me and say "I told you so..."

 

[Leebo]

I must have missed it but why whould we want to lower the FC/CYA ratio?

In the past I've seen people hundreds of times more knowledgeable than I speak out against the use of products such as phosphate removers, algaecides, clarifiers and so forth. Over the years these teachings have become a solid part of TFPC that will never change, add only what you MUST add to your pool water. The thing that got me time after time is as I read advice from these members every once in a great while they would reverse their advice and suggest the use of these products......but just for this one member. The member would follow the advice and as expected it would help the OP. As I read these threads my brain would always wonder, what factor was different about this one members scenario that make using these products acceptable? What was the key factor that allowed the user to benefit from using these products while thousands of other users carried on daily without them?

So far this thread has lead me to really look at scaling on SWG's when the users have high phosphate levels. This was something I never thought of before but it's something I'm researching deeper already. I thank all who have participated in this thread as you've already taught me at least one new thing. As I'm sure we all agree on, the first step in being able to teach something is to learn something.....which is something this thread already has done.

 

[MarianParoo]

So, at the end of the day, the burden of proof is on folks like me that choose to experiment. As I said in a previous post, I will keep copious notes and respond back and let you all know how the swim season went. I have "no dog in this fight", I am simply motivated by curiosity.

Thank you for being open, curious, and darn smart.

 

[Swampwoman]

+1

FWIW, I have emailed Hayward asking if they have any guidance in my case re: limits/levels of phosphate with an aquarite t15 set up...we'll see if that gets to anyone who might be able to answer since all their printed material so far in their troubleshooting guide says that if phosphates test high to consult a pool specialist

I have also written to Seaklear to ask if water temperature has any impact on efficacy, since I will be treating very cold water.

 

[Swampwoman]

Since we're more or less discussing deep-end outlier possible phosphate instances, I dug up an old thread that stayed with me about a poster with SWG who had metal staining that would remove with AA but return. He hasn't been on the forum since '13, but in his case he had a pool company come out that said they'd seen pools with high phosphates (eg over 3,000) end up with what sounds like iron phosphate staining...looks like iron, acts like scale. After a partial water change, he still had 3000 ppb iron. They reduced it to 1,000 and the stains went away.

He later pm'd me the name of the company that did it. Below, I am posting his quote of the outcome.

This may have been another unique case that's an outlier, OR the bonding issue may have been the true culprit -- or both, but its a data point for a discussion of "when" its a goid time to consider phosphate levels as a contributor to a problem.

I later learned that iron phosphate scaling was a real, but highly unusual, phenomenon...

confirmation of metal stains [Archive] - Trouble Free Pool
per RJ, who two months later reported the stains stayed away:

Update: We called in a professional pool company to analyze the water, and they found extremely high levels of phosphates (remember I had just drained/refilled one week prior to this). They said the phosphates were well over 3000, and had seen two other cases where phosphates this high would stain pools. They recommended PhosFree. At the same time, as a pre-caution, we did notice the SWG control panel was not in the bonding loop, and we attached the copper wire to the bonding lug on the unit. We used one 3L bottle of PhosFree, and within a day we saw a brown substance starting to floc together. After 2 days, we backwashed (very brown water), then vacuumed the floc'd up areas to waste, and noticed the pool wasn't as stained. We added more water (because we had vacuumed out quite a bit), then treated again with another 3L bottle of phosfree and waited 2 days, backwashed and vacuumed to waste. After 1 week, the stain is completely gone! I've never seen anything but ascorbic acid remove the stain, and we are, to say the least, shocked and ecstatic! We still have over 1000 phosphate level, but are now without stain! Our next step is to use the Phos Floc (which is made for levels over 1000) to try and get more of the phosphates out. We would probably have used this initially but couldn't get it locally so we had to order it online. Will keep you posted!

Per me, though darned if I can find my source material: (10,000-30,000 ppb added for clarity...people get the pPB/ppm thing mixed up a lot with pi4)

One more note, just for anyone reading.

Someone, I think Jbizzle, mentioned reading an article about phosphate scaling. I actually have since discovered that in theory at least, RR's situation could possibly be related to a phenom witnessed usually in water treatment where processed water has high (eg. 10-30 ppm phosphate or 10,000-30,000 ppb, just like my water - NOTE NOT 1 ppm or 1000 ppb like usually referred to in pool world) where phosphates can interact with calcium and cause something called calcium phosphate scale under certain conditions (not to be confused with carbonic scale).

The theory is a contender in my case because I have the known level of phosphates at 25 ppm, AND my fill water is about 350 ppm calcium BUT my pool only ever seems to read about 130 ppm...so where does the other 200 ppm go from the fill water? -- It is perhaps sequestered by the Jack's and Metal Magic...but could also be involved in creating iron scale, OR phosphate imbued scale coupled with iron, that makes it more difficult to treat with AA. Just a random theory at the moment. Eventually I'll figure it out if by mere process of elimination

PS I should note that both my calcium and iron are now significantly lower since upgrading to a dual softener and fixing the old one...which is why I never really bothered figuring it out The area with the historic faint stain that seemed a candidate for part scale has reduced with the use of Metal Magic, and what's left I decided not to care about as I cannot determine if its underliner or on the liner. If its under liner, I should treat surrounding soil with ferric sulphate, but the last thing I need is to introduce any more iron around here

 

[AUSpool]

^I do appologise Swampwoman, it does look a bit like there's two conversations going on hear but for what it's worth I think your doing the right thing to open early.

So, at the end of the day, the burden of proof is on folks like me that choose to experiment. As I said in a previous post, I will keep copious notes and respond back and let you all know how the swim season went. I have "no dog in this fight", I am simply motivated by curiosity. Hopefully I don't generate a green swamp but, if I do, it can easily be fixed and I'll post plenty of pictures of it so you all can make fun of me and say "I told you so..."

This is becoming a common theme but thanks again. I too love a good experiment, it's often the only way to cure an over active curiosity and I applaud you for giving it a go. I would never make fun of you or say "I told you so..." I wish I were half as smart as you and constantly wish I had tried harder and paid more attention through all those lectures.

It's interesting though as looking back on my historical pool data your about to go were I've been, although I suspect you'll use much better pool management and date collection practices. I've always had low phosphates due to lots of heavy rain events and used to run my FC at 3ppm and CYA at 45ppm. Due in part to poor management my free chlorine has been as low as 1.5ppm. A FC/CYA ratio of 3.3 and have never had a CC or algae problem that I was aware of.

Ever since I've adopted the TFP recommended levels my SWG cell has been spotless. I don't really know what it is but suspect higher CYA. Not long after raising my CYA to current levels I had a high chlorine level after replacing the cell and couldn't notice the high chlorine when swimming in the pool, I'm thinking that was due to higher CYA also.

 

[Patrick_B]

One more Aqua article that I dug up -- if you read it, be sure to also read the comments as well that address the wide variance of anecdotal "evidence" about what PO4 level might or might not be too high for problems with salt cells.

The article cites MFGs are recognizing over 500 ppb (so I'm 50,000 x too high but a pool tech notes he regularly has no problem with SWG units on 3,000 ppb of PO4.

Failing Salt Generators: The Phosphate Connection - AQUA Magazine

I've come back to this trying to understand, and have some curiosities.

They say that Po4 interference with SWG is to quote the article "somewhat theoretical." Why is this?

They do not mention CaPo4 scaling as a problem, but is it in a SWG? If it is, what are/would the saturation levels of said constituents? They say it's 500 PPB for Po4 but I'm wondering where the threshold would be for others in combination. Why don't they mention other constituents involved in this?

If it's just Po4 deposition on the SWG plates what does this look like I wonder, and what is the process for the reaction of the deposition if it's just phosphates being deposited? It seems like they are, but maybe that's not what they are saying?

To me, this SWG issue is as interesting as anything in the thread so far. Phosphate deposition ,or at least the potential for it should easily be able to be calculated like CaPo4 is, and that's what makes me curious. Or maybe it isn't, and that's what makes it theorhetical?

 

[JoyfulNoise]

swampwoman outlined some of the theoretical calculations that chem geek did for her in a long-ago post - Phosphates.....are they worth removing?? - Page 5

Basically you need a fairly high phosphate concentration for calcium phosphate scale to show up in your cell, something like 25ppm Now the reason why it finds itself as an issue in heaters is due to the temperature dependence and the fact that water heaters (and water boilers) have such high heats that calcium scaling of all kinds (phosphates and carbonates) becomes a very typical problem.