Algae despite good FC level...are phosphates to blame?

[Saturn94]

Dave suggested I start a thread here in response to my post in this thread;

EWKearns - phosphates - Page 2


Here's the relevant part of what I posted;

"...I had a situation last season where I got some algae growth on one wall despite keeping FC at or above the recommended target level (never below 6ppm FC with CYA at 70-80ppm...more typically 6.5-7ppm FC; I use a SWCG), maintaining borate level at 50ppm, and passing all 3 SLAM criteria with flying colors (edit: before the algae appeared). I do have to use a sequestrant (Jack's Magic Purple Stuff) to prevent staining (despite metals testing negative using the "bucket test" method), hence my interest in the phosphate subject.

I am not a new user and have been following the methods taught here for many years. Last season (late August) is the first time I saw algae and has me puzzled. Btw, a SLAM took care of it and it did not return the rest of the season (closed early October). After that incident I didn't let FC drop below 10ppm for the rest of the season."

Could high phosphate level be to blame? I've not tested for phosphates since its been taught here that it's irrelevant when maintain proper FC levels. I assume my pool might have a high phosphate level given the steady diet of Jack's Maguc Purple Stuff.

 

[duraleigh]

If your FC/CYA level is correct and you get algae in a certain area, that area is likely an area of poor circulation. The solution should not require any chemical addition.

Simply brush the algae off the wall up into the flow of chlorinated water and it will quickly be killed. Maintain all levels as you have been and observe to see if algae reappears in the same area.

If it does, you must change your flow pattern so that your properly chlorinated water can get to that algae and knock it out. Secondly, are you brushing the pool weekly?

I would not SLAM. Your issue should not require a SLAM. Being thorough, I might even try brushing the wall again, even if algae forms for a second time.

I assume my pool might have a high phosphate level given the steady diet of Jack's Maguc Purple Stuff.

Why? There is no correlation between phosphates and sequestrants that I am aware of. I have never used a sequestarnt so correct me if I am wrong.

The subject that brought us here was phosphates. I don't think they play a role in any reasonable pool problem and your issue certainly would not be affected by them one way or the other.

 

[Marcion333]

If your FC/CYA level is correct and you get algae in a certain area, that area is likely an area of poor circulation. The solution should not require any chemical addition.

Simply brush the algae off the wall up into the flow of chlorinated water and it will quickly be killed. Maintain all levels as you have been and observe to see if algae reappears in the same area.

If it does, you must change your flow pattern so that your properly chlorinated water can get to that algae and knock it out. Secondly, are you brushing the pool weekly?

I would not SLAM. Your issue should not require a SLAM. Being thorough, I might even try brushing the wall again, even if algae forms for a second time.

Why? There is no correlation between phosphates and sequestrants that I am aware of. I have never used a sequestarnt so correct me if I am wrong.

The subject that brought us here was phosphates. I don't think they play a role in any reasonable pool problem and your issue certainly would not be affected by them one way or the other.

Based on Duraleigh' suggestion of a possible area of poor circulation, you can simultaneoiusly test that area's chlorine level an another pool area to see if that area has a lower level.
Please post your results if you perform this test.

Phosphate removers are products like Orenda PR-10000, SeaKlear, and Phos free (regular and extra strength). These products contain lanthanum, a rare earth mineral.

 

[Saturn94]

Part of what puzzles me is I haven't changed the circulation pattern; I point the return eyeballs so that the water circulates around the entire pool in a circle; it appears the spot in question should be getting good circulation. I'm also maticulous about maintaining proper levels per the teachings here (no pool store antics for me!).

I must admit I do not manually brush every week. I do run my Polaris 280 at least 3 times a week, which helps circulate water and has a tail sweep which brushes the pool liner.

This circulation pattern and use of the Polaris has worked well for many years without any algae appearing.

But now that you mention it, there was one change last season. I was reading a discussion on wether or not main drains were necessary. The resident experts here said main drains are unecessary and have little/no impact on cleanliness/water quality. So, to increase skimmer efficiency, I partially closed the main drain valve (it did increase skimmer efficiency). Could this have altered the circulation pattern just enough to cause an issue? If so, wouldn't the algae have appeared soon after instead on months later? Perhaps as a test I'll keep the main drain open this season and see if the algae returns.

My understanding is that HEDP (correct term?) based sequestrants, like Jack's Magic Purple Stuff that I've been using for years (successfully), add phosphates to the water when they break down. If true, I wouldn't be surprised if the phosphate level in my pool is high.

I completely understand the idea taught here that given proper FC levels it shouldn't matter how much "algae food" is in the pool. After all, dead algae can't eat. However, even some if the "experts" on TFP admit high phosphates could be an issue in some (rare?) circumstances. Is this one of those circumstances? I don't know, hence my exploring any potential causes and solutions.

 

[Saturn94]

Based on Duraleigh' suggestion of a possible area of poor circulation, you can simultaneoiusly test that area's chlorine level an another pool area to see if that area has a lower level.
Please post your results if you perform this test.

Phosphate removers are products like Orenda PR-10000, SeaKlear, and Phos free (regular and extra strength). These products contain lanthanum, a rare earth mineral.

Now that you mention it, I take the water sample from the same area each time; deep end, elbow deep, south side of pool (that wall faces north).....that's real close to where the algae appeared.

The pool is still closed right now. I normally open the first week of May (with clear water and no visible algae ).

 

[pikeman]

I think more brushing is the answer. My pool has pretty good circulation, but if I either forget, or go out of town on business there will be a green area on the south wall of the pool. When I am diligent with the brushing it does not happen. I routinely have 3-5ppm FC, and never any combined chlorine.
Pete

 

[Patrick_B]

Saturn, I would be lying if I said I knew that's what was causing your problem. Could it be a contributor? Sure phosphates could be a contributor, but if it were, I tend to think you'd see this in more areas of the pool, not just one, and you'd see it consistently. Unless of course it was Mustard Algae. In that case, it could be isolated to a shady area. But you don't seem to indicate that.

If the source of those Orthophosphates is from your Purple stuff, I don't know if a Phosphate remover/inhibitor would be the answer in your case. I say that because I don't know if, or how much one you added would interact with the Phosphonate metal sequestration components in the Purple stuff. Someone who understands the remover/inhibitor chemistry will have to help me on that. Without knowing, I wouldn't want to risk that before I understood it better. If you need the Sequestrant, I'm sure you'd agree that's not something you'd want to risk disrupting. With that in mind, I would first explore the possibility of it being a circulation issue. If so, this might be remedied with more frequent brushing, or a change of your returns direction. Not saying it's the issue, but it too could be a contributor, and I'd want to rule it out. You said that's covered, so of course I also have to add that low FC residuals have to be considered. I know you said that was covered too, but I've certainly faltered on mine at times, so I'd want that ruled out as well. It's just covering the basics is all, and no one's pool balance is always perfect.

So if you're curious, I'd say get a Po4 test and find out once you've eliminated the above, and explore the options of a remover for yourself. There's nothing wrong with wondering or asking the question, or trying to address it in that manner if you want too. Or, you can continue the bump of FC a point or two above normal levels that seem to be working for you. It's a choice for you or anyone else to make in what works best for them in terms of ease and cost. If I'm not mistaken, 3000 PPB Po4 is where the use of removers begins to make sense. I keep reading >1000 is of concern, but I question that largely based on my field experience. We actually add many, many more times that much Opo4 into industrial water systems on purpose, (8-12 PPM) and reasonably manage algae growth with less than one PPM FC with zero Cya, so I know it can be done EASILY in a simple swimming pool without worrying over Phosphates.

I will never say flat out that Po4 removers can't help, or don't work at all, but I'd gladly accept the challenge to run double the Phosphates in my pool the industry says is unmanageable, and I'd do it without one drop of remover. I can say with a lot of experience, and much confidence that it would be quite easy to do.

But to answer your earlier question where some use of it might be helpful, one would be where a person had a very high phosphate level, and wanted to use the remover/inhibitor to help lower his Chlorine usage some with the addition of one. It's my firm opinion that the cost benefits are not often there to justify it because the removers are pretty expensive relative to Chlorine generally speaking. Additionally, it's another balancing act to perform and maintain with your chemistry, and to me thats a very important factor. It's more advanced, and it's why we shy away from it as a basic tenant of what we teach.

No matter how you slice it, it's more advanced chemistry relative to basic pool maintenance that we know works, and works exceptionally well. This is why we don't want it becoming part of our basic nomenclature in the TFPC methods.

 

[Marcion333]

I don't see why your drain change couldn't be to blame. In medicine, it is said that "When you hear hoofbeats, think of horses (common things), not zebras (rare things)."
Purple Stuff contains 1-Hydroxyethylidene-1, 1-diphosphonic Acid.

 

[Patrick_B]

In medicine, it is said that "When you hear hoofbeats, think of horses (common things), not zebras (rare things)."

This is a good description of our basic tenants. Normal, average, simple stuff first. Horses appear far more often around here than Zebras.

 

[Marcion333]

Even with the drain change, it's possible that you wouldn't have this one area of algae growth if your phosphate level was low.

 

[duraleigh]

I think more brushing is the answer. My pool has pretty good circulation, but if I either forget, or go out of town on business there will be a green area on the south wall of the pool. When I am diligent with the brushing it does not happen.

Saturn, I think your answer is in pikeman's post. Frequent brushing of the sides of a pool is mandatory if you use the TFP ideas we teach.

Since this thread is supposed to be about phosphates and their potential benefits. I will repeat that phosphates in your pool or not......they are not relevant.

 

[Saturn94]

Thanks for the replies.

Patrick,

Perhaps as you seem to indicate there's not a single issue that caused the appearance of algae, but a combination of things coming together (lucky me! Lol).

Like you, I don't want to jump into phosphate removal without knowing how it will react with the sequestrant. I use to add a phosphate remover at closing (stopped doing this several years ago) and can tell you it turned the pool into a milky mess. The water would be clear when I opened in the spring, but it would take some time to vacuum the mess that settled on the bottom of the pool. There's also the issue of cost; Phos removers aren't cheap.

Out of curiosity, I might order the Taylor test kit for phosphates and see what I come up with. It may not matter, but could be interesting.

I doubt FC ever dipped below target. I test frequently and the SWCG does an excellent job maintaining FC (I run the pump 12hrs during the day). It would be very odd if FC dropped significantly between tests then went back up before the next test. SWCGs are great for maintaining FC, but not so much for quickly raising FC (I use bleach if I want to raise FC).

My pool has always seemed sensitive to algae growth. Maybe it's because we are surrounded by water here at coastal SE VA (we're about 1/4 mile from the Chesapeake Bay) and get a lot of algae spores flying around? I can tell you if I kept FC at the minimum recommended level for a SWCG, 4ppm, the liner would quickly become slick (start of algae breakout?). When I was using the pool store many moons ago, they told me to bump FC to 4-5ppm once water temp reached 80° since the "normal" recommended levels, 1-3ppm, wasn't working (of course I know why after discovering these forums). I quickly learned at that time the absolute minimum I needed for my pool was 5ppm (I was also using an algaecide and borates at this time). Fast forward to after I found the forums and going forward I wouldn't let FC drop below 6, and stopped using an algaecide on a regular basis. Since then I haven't had algae until last season.

I did think about mustard algae. I've not seen mustard algae before, so I'm not sure what it looks like. This algae was green and had a slimy texture (I touched it carefully to see what it felt like). It looked like typical green algae to me. I hope it's not mustard algae....from what I've read it's a PITA to treat.

Btw, I should note I'm not one of those looking to maintain FC at the absolute lowest level possible. I'd rather have some wiggle room rather than maintain my pool on the razor's edge of an algae outbreak. At the other end, I'm also not interested in running FC so high that I'm wasting money unnecessarily.

Marcion,

The change in use of the main drain seems to be the only variable from previous seasons, so perhaps you are correct that it had a negative impact that contributed to the appearance of algae. Perhaps your also correct this would have happened if phosphate level was low. So, do I try to lower phosphates (is this possible with the continued use of HEDP sequestrant?) or just maintain a higher FC level? Or just keep FC where I've been keeping it and just manually brush more (I hate manually brushing..lol)?

Dave,

I appreciate where you're coming from. I'm still not convinced phosphate level isn't a factor at some level. I'd love to read feedback from our chemistry experts here on this subject. I gather such a conversation would be allowed here as long as it doesn't take the form of telling newbies they need to worry about phosphates before getting a handle on the basics first? I hope so. Perhaps we'll all learn something new.

That said, based on the conversation here, I think my next step will be to resume using the main drain normally and add some manual brushing sessions to my pool care regime.

I see tracks, but so far no horses....maybe I do have a zebra?

 

[Patrick_B]

One of the experts has spoken.

Perhaps not the one(s) you might want, or in the way you wish, but one has spoken nonetheless.

:lol:

 

[Saturn94]

One of the experts has spoken.

Perhaps not the one(s) you might want, or in the way you wish, but one has spoken nonetheless.

:lol:

And it's appreciated.

In the interest of learning, I'd love to read the input of more on this subject and the reasons for their positions.

 

[Marcion333]

I am not a pool chemical expert, but an expert did tell me that i should be able to keep my FC/CYA ratio lower than 7.5% in my low-phosphate pool and still avoid algae growth, maybe an FC/CYA ratio as low as 3% but i haven't let it go below 5%. So far, no algae growth, crystal clear water, and lower chlorine usage and expense. Phosphates are relevant to me.

Please note that i do not have a SWG pool. i do not know if you can use any of this information with your SWG pool.

 

[Saturn94]

I am not a pool chemical expert, but an expert did tell me that i should be able to keep my FC/CYA ratio lower than 7.5% in my low-phosphate pool and still avoid algae growth, maybe an FC/CYA ratio as low as 3% but i haven't let it go below 5%. So far, no algae growth, crystal clear water, and lower chlorine usage and expense. Phosphates are relevant to me.

Please note that i do not have a SWG pool. i do not know if you can use any of this information with your SWG pool.

I think the "fly in the ointment" for me is the need to add a sequestrant and its impact on phosphate levels. There are non HEDP sequestrants available (i.e. Jack's Magic Magenta Stuff), but as I understand it they are not compatible with polyquat algacides (I use polyquat for winter closing).

Do you find you can keep phosphate levels low cheaper than maintainin a higher FC/CYA ratio?

 

[Patrick_B]

If I'm not mistaken, Marcion started with Zero phosphates in the pool.

 

[Saturn94]

If I'm not mistaken, Marcion started with Zero phosphates in the pool.

Ah....so just maintaining low phos levels.

If I didn't like the convenience of my SWCG so much I'd switch to manual chlorination (for some reason I only get staining when running the SWCG) so I wouldn't have to use a sequestrant. Then again, I've not tried manual chlorination for any extended time (more than a couple weeks). Perhaps I might still get staining in the long run? That's a different topic though.

 

[duraleigh]

I'm still not convinced phosphate level isn't a factor at some level. I'd love to read feedback from our chemistry experts here on this subject.

The qualifier "at some level" is important. It may be at some level but a level that TFP feels is not important enough to be included in what we teach.

Incidentally, this position is the position of 7-8 people who I consider to have the best minds for chemistry. It was not arrived at willy-nilly but rather talked about and evolved over a long period of time. years, in fact.

I gather such a conversation would be allowed here as long as it doesn't take the form of telling newbies they need to worry about phosphates before getting a handle on the basics first? I hope so. Perhaps we'll all learn something new.

the conversation about newbies is already here on the forum.....you just posted in it more than once. (and NOTHING was "not allowed") Why do you think it is not allowed when you just participated? I am not really sure why you said that.

 

[Marcion333]

I think the "fly in the ointment" for me is the need to add a sequestrant and its impact on phosphate levels. There are non HEDP sequestrants available (i.e. Jack's Magic Magenta Stuff), but as I understand it they are not compatible with polyquat algacides (I use polyquat for winter closing).

Do you find you can keep phosphate levels low cheaper than maintainin a higher FC/CYA ratio?

Why do you use a sequestrant???

Regarding, "Do you find you can keep phosphate levels low cheaper than maintainin a higher FC/CYA ratio?" I now use Orenda PR-10000 phosphate remover. I bought a gallon of it; i don't remember its cost, but a gallon of it wasn't inexpensive. However, an Orenda company person told me that it contains 5 to 6 times the active ingredient compared to Phos Free so I only add about 2 ounces a week. I estimated that my last phosphate reading using an Aquachek one-minute phosphate test was around 10 (color estimate based on the enclosed color chart). 1 gallon at 2 ounces a week will last me 64 weeks.

So this product lasting over a year plus somewhat lower chlorine cost over a year plus algae insurance seems like a good deal to me even if I didn't save money overall.

A special shout-out to the expert who gave me the phosphate tip; thank you very much!!!

Patrick, my initial phosphate reading in November 2015, when building the pool was finished, was around 750 ppb.