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

[Saturn94]

Thanks for the update.

 

[JoyfulNoise]

STARLOG Update 2017:

I've been remiss in reporting this summer, but here's a quick summary:

1. After fresh water change, I did not treat during winter in dome for phosphates due to floccing tendency in high concentrations and inability to use vac to waste in dome conditions.

2. pO4 level is now 25,000 ppb despite a full water change last year and a much "lighter" diet of sequestrant and keeping calcium in the 200 range, which using soft water, has meant adding. So any theories about age of water, swamp recovery, etc. are in fact ruled out now...this reading is from a year of sequestrant use on water that started out at 1,700 ppb po4.

3. My swg cell on annual inspection and cleaning showed no scaling. It is designed to she'd scale, and it does.

4. My swg output indicates it is fully capable of generating its rated 1.45 lbs of chlorine as in 24 hrs.

5. My heater is operating perfectly, though I still get the turquoise scale. Testing this year shows the ratio of scale component to be roughly 10 parts po4 to 3 parts copper to 2.5 parts iron.

6. I've hired a Raypak tech to come out mid-Sept to inspect and clean the cupronickel exchanger and plan to take pics. One part curiosity and one part possible preventative maintenance to ensure no operational failure during winter.

7. I have both alum floc and a gallon of commercial Seaklear lanathum chloride on hand. I've not decided about treatment plan yet before the dome goes up. I may not bother, as I may find that so-doing just removes my sequestrant.

8. It goes without saying for those few hardy souls who've followed this thread, but for posterity, despite the crazy po4 level as tested by Hanna hi range meter, I've never once had even an inkling of algae, or even cloudiness suggesting nascent algae forming. So I think we can safely put to bed any notion that po4 mgmt is required for any reason outside of a desired to run the lowest FC possible experimentally, and possibly that po4 mgmt is near futile for folks on well water who don't want stains.

Even if the exchanger is full of scale and its lifespan reduced, I'm not sure there's an alternative option in my case that would meet my objectives, short of periodic inspection and cleaning of heat exchanger.

Swampwoman and I agree on all points. As for the JoyfulNoise 2017 Update here are my results -

PO4 < 150ppb all season
FC 3-4 ppm all season
SWG 40% all season
Pump run time ~ 6 hours for SWG active --> 2.4 hrs/day FC production or 2.2oz/day of chlorine gas or a 1ppm/day FC loss
CYA ~ 90 ppm all season

Algae .... nada!

I would not feel safe keeping my FC/CYA ratio that low unless I knew my phosphates were low. I also kept my borates up at 60ppm this year. With those two factors, I don't worry about algae at all.

SW,

Your phosphate numbers are consistent with your sequestrant use. Initial doses of HEDP can be as high as 30ppm while maintenance dosing is usually around 10-15ppm HEDP. Without knowing the exact specifics of chlorine oxidation of HEDP, it's hard to know what their dosing would result in in terms of orthophosphate, but it certainly looks like you're getting a pretty hefty input rate of phosphates.

Have you ever measured your nitrate levels? You can get a nitrate test for about $10 at the fish store (ammonia and nitrites should be 0). If we knew your nitrate levels we could calculate your Redfield Ratio and see where your pool water lies on the favorable algae formation chart -

Redfield Ratio - The Free Freshwater and Saltwater Aquarium Encyclopedia Anyone Can Edit - The Aquarium Wiki
Redfield ratio - Wikipedia

 

[needsajet]

This has been very interesting to follow. Thanks for the updates

 

[Swampwoman]

Hey joyful, swamphubby has a nitrate kit for his salt water Aquarium. Maybe I'll see if he'll test it tomorrow. We're kinda compartmentalized around here. I don't touch his kit and he doesn't touch mine

And I might add that I have no algae and he's constantly at war with it

 

[JoyfulNoise]

Hey joyful, swamphubby has a nitrate kit for his salt water Aquarium. Maybe I'll see if he'll test it tomorrow. We're kinda compartmentalized around here. I don't touch his kit and he doesn't touch mine

And I might add that I have no algae and he's constantly at war with it

Sounds like he needs to check his Redfield Ratio and maybe do so phosphate reduction ?

Let me know what your Raypak service call comes up with. Hopefully not too much calcium phosphate scale built up on your heat exchanger (though I doubt you'll find any).

If only the chemical suppliers used PBTC instead of HEDP. PBTC has a much higher chlorine tolerance than HEDP. Although, interestingly enough, bromine turns out to be far more destructive to HEDP, ATMP, etc than chlorine is. So no using any Yellow-Out in your pool [emoji6]

 

[Leebo]

PO4 < 150ppb all season
FC 3-4 ppm all season
SWG 40% all season
Pump run time ~ 6 hours for SWG active --> 2.4 hrs/day FC production or 2.2ppm FC loss
CYA ~ 90 ppm all season

Looking at these numbers two of them stick out, a FC level of 4ppm and a CYA level of 90. Checking PoolMath a FC level of 4 is still within the target area for a CYA level of 90. Couldn’t your lack of algae be due to you maintaining a proper FC level??

 

[JoyfulNoise]

As per the Chlorine/CYA chart -

Note 3: Most saltwater chlorine generator (SWG) pools appear to prevent algae at a minimum FC level of 4.5% of the CYA level as compared with the roughly 7.5% of the CYA level shown in the "Min FC" column for manually dosed pools.

With 90ppm CYA, 4.5% equates to 4ppm FC and remember, that's a minimum recommended level (I'm supposed to stay above that at all times). What I should have said was that my FC was never higher then 3-4ppm. So, at most, I just barely maintained the minimum FC/CYA ratio for an SWG pool. According to TFP Standards, living at the minimum is flirting with an algae bloom. Never happened. Never had an OCLT of >1ppm. Pool remained crystal clear all season. And, if I go through my super-duper-awesome historical data as stored on The PoolMath App (which always makes me want to test a lot more), on June 10th, 2017 (outdoor temp was >101F according to AccuWeather and pool temp was 84F), I had a reading of 2.4ppm FC.

2.4/90 = 2.6% ratio

Hmmmm, pool was clear, no bleach was added, SWG output was bumped up by 5%, FC back up to the 3 range the following test. Where's the algae bloom???

I guess I'm just really, really, really lucky.....darn, I need to hitch a ride to Vegas or buy some lottery tickets....

All kidding aside, I think the take-away from my numbers and my historical flirtations with phosphates is this - careful management and use of secondary sanitation control methods allows me to operate the pool at a point I prefer (ie, lower chlorine levels). For me, that works fine. For others, they may not have the time or desire to fiddle with a pool and tweak things, ie, they just want a bucket of water to swim in. So, pick your operating point and manage your pool accordingly.

What's of interest to me are people that suffer from recurring algae problems even when they try super-hard to maintain TFP standards....I really wonder if those folks would be helped with a reduction in phosphates in order to make their pool water less reactive to algae blooms. If only there were some folks like that who would be willing to maintain proper TFP standards and lower their phosphates.....hmmmm...wish I knew someone like that.......

 

[JamesW]

What we really need is a proper scientific study that uses multiple pools with varying phosphate levels to see if they make any difference.

Random anecdotal reports have limited value.

Are there any cases where reducing phosphates can help? If yes, what would be the criteria to suggest it?

 

[JoyfulNoise]

Sadly, this topic almost always devolves into a discussion that misses the forest (globally lower chlorine levels) for the trees (specific arguments about algae). But, for the sake of completeness, let's deal with trees first -

I think the various water quality studies have already shown that algae is susceptible to environmental manipulation. If you look at those links in my previous posts to the Redfield Ratio, you'll see that water low in phosphorous and nitrogen doesn't favor the formation of green algae. Blue-green algae is more favorable in low N water but that's not even algae, it's Cyanobacteria. Without phosphates, chlorophyll does not form properly and so algae has a very hard time getting started until enough organic matter has built up in the water to provide sufficient concentrations of nitrogen and phosphorous. I have researched several sources on the topic, but this in-depth study of Klamath River Modeling Project has some of the more relevant data and references.

http://www.krisweb.com/krissheepscot/krisdb/html/krisweb/biblio/klamath_ucd_deasorlab_1999_wq.pdf

But here's some quotes from page 56 & 87 regarding phosphates as nutrients -

Generally a phosphate concentration of 0.01 mg/l will support algae species. (Page 56)

And

All models illustrate the importance of phosphate in aquatic systems. For example, equation 4.16a illustrates that each atom of phosphorus (as phosphate) added to an aquatic system can result in the fixation of about 106 atoms of carbon in organic matter. Further, when the organic matter produced from one atom of phosphorus decays, as per equation 4.16b, it has the potential to consume 138 molecules of oxygen (Drever, 1988). (Page 87)

Controlling phosphates is just another way of manipulating the aquatic environment to achieve a desired outcome. Limiting phosphates limits growth and, in the extreme, eliminating phosphates results in no life at all. So the science here really isn't worth chasing down. When you combine a very potent sanitizer (i.e. chlorine) with a reduction in available nutrients, water will remain sterile for long periods of time.

So now back to the forest - lower FC levels. Let's assume you agree with the above that phosphates affect the way algae can grow and let's assume chlorine is a good sanitizer. The bulk of chlorine loss in any given day is from UV exposure. The next biggest loss is from oxidation of bather waste. UV loss will consume about 1 to 2ppm or so of FC per day depending on where you put your CYA level at and bather waste takes about 4 grams of chlorine per person-hour. In a 15k gallon pool with 2 people swimming for an hour, that's about 0.14ppm FC. Algae and bacteria make up the rest of the loss which is to say, not very much. However, once algae starts to grow, it can accelerate rapidly if nutrients are available and then very quickly cause the FC to bottom out. So, by limiting nutrient levels, one removes a possible source of FC depletion and then all one needs to do is worry about UV loss and bather load. This requires lower levels of chlorine to be maintained and thus allows a pool owner to operate at lower target FC levels. If you need only half as much chlorine per day, then that saves money.

In the bigger picture, who is going to benefit and what will those benefits be? It's hard to say a priori. I think it just comes down to pool owners giving it a try. At most it's $40 bottle of chemical (for the good stuff). That's not really a budget buster and, if input sources of phosphates are low, then it could represent a few years worth of treatments. I don't think that's a huge burden on most pool owners if they wish to try it out. The important point is to get the pool balanced and clean first, then reduce phosphates. A phosphate reducer will do nothing for a pool that is already green with algae and this is where the pool stores get it all wrong and lead people astray. The unfortunate casualty in all this is that perfectly sound and banal chemical treatment gets a bad rap because the pool industry decides to use it as a money making ploy.

But again, if all you want is a bucket of water in your backyard m to swim in and you don't particularly mind keeping chlorine levels on the high side, then no need to change. The important thing is to find the pool care method that works best for you and stick with it.

 

[Leebo]

Sadly, this topic almost always devolves into a discussion that misses the forest (globally lower chlorine levels) for the trees (specific arguments about algae). But, for the sake of completeness, let's deal with trees first.

Ya know, I find this comment VERY interesting as for me, globally lower FC levels never were the reason I personally started to look at this subject. It now casts a different light on things somewhat when you change the users “goal.”


Some let’s take a step back and look at a few things here. As you mentioned this topic frequently goes in circles as I’m not sure there is a perfect answer. We all can agree that chlorine is an effective sanitizer, but can we all agree that reducing phosphates is worth the average users time? For starters I think it’s safe to say we all agree that ignoring phosphates and maintaining the FC/CYA ratio will result in a clean pool year round. Additionally I think it’s safe to say using only chlorine and ignoring phosphates will result in a program that is considerably cheaper and easier than the average pool store will have you follow.

 

[JamesW]

In your opinion, is it worthwhile for everyone to test for phosphates?

Is is worthwhile to treat for phosphates?

If yes, what level of phosphates should one try to achieve?

 

[needsajet]

I could try this Matt, and be one data point. Maybe 3 data points if it's easy cause I do three pools. I see it kinda like borates. I don't need it so I don't have it, but very willing to give it a go and compare two prior years as a benchmark. After all, TFPC wouldn't be a thing if not for past pool enthusiasts reporting numbers and gathering empirical evidence!

I ran my numbers and based on $465 for a replacement SWC cell, and if I could use 1 ppm less FC in swim season and 0.5 ppm less in off-season, that's around $30 bucks a year, so would make sense if demonstrated across more data points. If I was on 128 oz jugs of 8.25% at $2.00, it's more like $75, so this certainly seems like a valuable exploration.

 

[Swampwoman]

In your opinion, is it worthwhile for everyone to test for phosphates?

If we adhere to a KISS principle in TFP guidance, I'm not sure we could recommend testing due to the variables that first have to be sorted.

1. Anyone on well using HEDP would not qualify due to test limitations (see below). This does not mean they should stop using HEDP. Plus, if they've been using HEDP and switch to EDTA they could end up with a cloudy mess that we don't know how to help resolve short of complete oxidation, negating any sequestering action and countermanding the do-not-slam anti-stain/tint measures.

2. The inexpensive test strips and kits are limited to 1,000 ppb (Taylor)...with the highest capability 2500 ppb. And yup, the test strips are guess strips. I went to 3 pool stores as an experiment and got guess strip readings ranging from "just under" whatever the limit to one "you're over" (on the 2500 ppb strips.)

Meanwhile, at the time, my po4 was actually 10x higher than any of them guessed.

My test kit was $50. (Hanna Instruments). Its range is 30,000. Its colorimetric and only partway towards pro. Pro gear for po4 costs much more. I do think the Hanna is reasonable accurate as I've cross-corroborated results with distilled water in an aquarium kit.

3. Many municipalities will have po4 in source water from the use of HEDP to protect pipes (a notable exception being Flint Michigan, who felt it too expensive.). My trucked water had 1750 ppb. But at source, the HEDP may still be in phosphonic acid form, which doesn't read until worn down/oxidized by extended exposure to chlorine.

4. Pentair currently claims 500 ppb as "proper water parameters" for its swg warranty. Nobody else considers that a "real world" number. Matt, however, is in compliance

5. While po4 is the most "ready" algae food, organic phosphates - which you cannot test without enzyme reduction, oxidation, and boiling - are also a source of algae food. So situationally, I'm not sure we could say "Your po4 is low so keep your FC at X" with any confidence. I might be wrong about this...we'd need to ferret out role/rate of organic phosphates in algae nutrition.

So, my inclination would be to advocate testing in the following way, if at all:

1. Are you on well/have metals/have ever used HEDP sequestrant. Pass.

2. If not, test your source water first. If reading is above 1,000 ppb, pass.

3. If your source water is less than 1,000, and/or you have a Pentair swg, test your water. If upper limit of test, buy Hanna tester or pass.

4. If you're still here with us, try normal dosing of Seaclear commercial and record difference. Maintain if effective.

5. If you want to control po4 from source water or to Pentair's limit and have higher numbers, know that high doses (eg gallon) of Seaclear or any lanathum chloride product will floc and sink. You must be able to vacuum to waste, and you will need to do so for about 3 days running.

So perhaps a majority of folks would be in category 4 - in which case, it may make sense. But without the firm facts that still seem to elude the industry itself, and even experts in the industry, I'd have a hard time with it myself.

 

[Catanzaro]

My phosphates (when the pool store used to test) were always low. I have even flirted with lower levels than 7.5% of CYA (around 5%) for a chlorine pool, and have never had any issues with passing the OCLT, algae problems or clear water. My pool has great circulation. This is all based on a 12 hour per day run time. There is very little that falls into the pool (beside a few leaves, some worms and dirt). Definitely would not recommend this to anyone.

Then again, I have friends with higher levels than even recommended, poor circulation with algae spots, etc. My neighbor who has had issues for 13 years finally switched over to liquid and his CYA is at 30 vs. 70 now. If his levels drop below the 7.5% minimum for one day, the water becomes cloudy and he has to SLAM for at least 2-3 days before everything is normal. His main drain/skimmer/return combination is limited. We added 2 rotating heads on all the returns and it appears this has been helping.

Now, that I am on an SWG, my CYA is at 70 here in NJ, and next year I will flirt around with lower levels of 2-3 ppm to see how it goes. Now, the time is getting near to close the pool. The weather is lousy, wet and cold.

Great thread and have been following this for a while! Thanks!

 

[needsajet]

Thanks for the great explanations

Thinking of situations where metal and sequestrants are not part of the picture, can a pool owner floc with lanthanum chloride multiple times, until no (or little) precipitate is noticed? Just a thought, but maybe we could brainstorm a simple method, to meet the KISS desire. It could be tested and potentially verified, if that's how it turns out.

The TFPC system would remain simple enough. Newbies (or the less enthusiastic) can stick with the basic recommended levels. Newbies don't need CSI or borates either.

Our predecessors worked through a lot of complexity to challenge the status quo. Imagine the early conversations about FC and CYA!

 

[JoyfulNoise]

The goal is always zero phosphates or as low as possible. So it doesn't really matter how high they are to start with or where the test maxes out at. For the Taylor test ($11 by the way), there's a high limit version that goes up to 2000ppb but it's not necessary, just use water dilution if you max out to get a feel for where you are. Most commercial grades of PO4 removers can handle 10,000ppb per 10,000 gallons of pool water per quart of of product administered. Application/treatment rates vary. SeaKlear and Orenda commercial grade products are the best.

Swampwoman,

On a scientific note, most researchers don't count organic phosphates because most living organisms can't incorporate phosphates from the environment in organic form (bacterial degradation of biomass is required to release inorganic phosphates). Algae especially only uses inorganic phosphate and at one point some would argue that the N ratios should have included both forms. But, since only inorganic phosphates are utilized, one uses that and then measures the cycling rate of the water - how quickly organic phosphates are converted to their inorganic forms. In high cycling water environments you can measure and include both forms. But in low cycling environments, it's only important to know what the orthophosphate levels are (see 3.6.2 and 3.6.3 of the study I linked to).

If a pool owner regularly uses sequestrants (most of which are HEDP), then don't bother with phosphate removal, it's pointless. However, in my pool, my input PO4 source is only environmental (leaves, bugs, etc) and so I have minimal PO4 increase throughout the season (~ 250 to 300ppb per year). In that scenario, a single treatment can last a long time.

 

[Swampwoman]

That makes sense.
I believe I recall reading a few years back that bacteria does/can feed on organic phosphate, but that would be moot due to fast kill times of chlorine, right?

Needajet, re:

can a pool owner floc with lanthanum chloride multiple times, until no (or little) precipitate is noticed?

Yes they can. But in the case of a well-water/sequestrant user, Im not sure it would be cost-effective compared with higher FC usage, though its debatable.

For example, last year I spent $119 plus shipping for the lowest price-per-gallon of Seaclear's commercial strength, which will in theory remove 9,000 ppb per quart per 10,000 gallons.

So the gallon would net me a reduction of about 15,000 ppb in a 24k gal pool.

At the time, that left me with 25,000 ppb, which would have taken another gallon and a half to treat. So at $320, I decided instead to put that toward a water change That amount would also almost get me a new T15 cell

This year, despite lower metal levels and reduced sequestrant use, I've gotten back up to 25,000 ppb from 1750...so a rate of decay of about 2,000 ppb per month I'm guessing. I know by Nov when I installed the dome I was already at 7,000 ppb.

So, in terms of clearing from sequestrant, I'd likely need a little better than half a quart a month, which is about equal to the amount of sequestrant I use cost-wise. I may resort to that if my heat exchanger turns out to have po4 scale when I have it cleaned.

 

[JoyfulNoise]

That makes sense.
I believe I recall reading a few years back that bacteria does/can feed on organic phosphate, but that would be moot due to fast kill times of chlorine, right?

Yes, chlorine would kill the bacteria that would cycle the phosphates through the water......

BUT (you knew there was a "but" coming....)

Your chlorine levels (and SWG) are cycling your phosphates just fine, no bacteria needed You need to contact your spies inside the sequestrant world and see if any of them use PBTC instead of HEDP. PBTC is much more resistant to oxidation by halogens.

I think you may need to consider an NSP and get off the crazy-train of sequestrants use. Or, just go all Zen and accept ugly brown stains on your liner, save your money and buy more beer....beer makes everything better [emoji481]

 

[Saturn94]

What's an "NSP"?

 

[JoyfulNoise]

What's an "NSP"?

Natural Swimming Pool....aka, backyard swimming pond. Complete with lots of [emoji196][emoji217][emoji216][emoji221][emoji887]

I was being cheeky with SW