Phosphates Will Kill Your Chlorine????

mmcwhorter

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Bronze Supporter
Jul 13, 2015
264
Huntingtown, MD
Yesterday.... while getting my water tested for Iron (and trying to find some MA that was actually out of stock)

My local pool store dude reported to me yesterday that my high phosphate level of 179 will tend to reduce and even kill my FC in the pool. I told him it was my understanding that the ONLY issue with phosphates is that its Algae Food...and if there are NO Algae in the water...then who cares?? I explained how I SLAM my pool each season when I open it...and using my a) SWG and b) Nautilus CC Plus...I have pretty much a "Trouble Free Pool" all year with the exception of the most mundane maintenance.... To which he said..."no, Phosphates will reduce or kill the level of FC thus causing algae to bloom or it will make your SWG work too hard"...What??? Say What??? I just smiled and said: "Thanks, have a good day".
 
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IceShadow

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Jun 8, 2019
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There's anecdotal evidence including from members on this forum that a high level of phosphates can reduce the output of some SWCG.

But like...1500-2000ppb high. Not 179.
 

mmcwhorter

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Jul 13, 2015
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Huntingtown, MD
To be clear: the number I reported of 179 ppb for phosphates was my FILL WATER (as I had just completed an Iron Stain Removal using AA and I wanted to test for Iron in the FILL WATER....TO BE more CLEAR: MY POOL WATER AS IT WAS A MONTH AGO reads 1600 ppb for Phosphates at the pool store...i don't see any evidence of a problem with my IC-40 SWG.....and I always thought to ignore it.

As mknauss suggested...read the manual...I found this tidbit from the Pentair IC40 manual:

Nitrates and Phosphates can cause extremely high chlorine demands and will deplete chlorine from your swimming pool. In some cases nitrates may even lower your chlorine levels to zero. Your local pool professional can test for nitrates and phosphates. While a 0 ppm level of nitrates is the ideal, the pool owner should make sure that nitrates DO NOT exceed 10 ppm. Phosphates should not exceed
125 parts per billion (ppb).

SO...SHOULD IT REDUCE MY PHOSPHATES? Again, my pool has no trouble staying at or above 7 ppm (CYA around 70)....and in fact it was staying above 10 ppm FC up till about a month ago when I reduced run time and % on the IC-40.

And if the fill water is 179...I wonder where are the Phosphates coming from?

Thanks
MM
 

IceShadow

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To be clear: the number I reported of 179 ppb for phosphates was my FILL WATER (as I had just completed an Iron Stain Removal using AA and I wanted to test for Iron in the FILL WATER....TO BE more CLEAR: MY POOL WATER AS IT WAS A MONTH AGO reads 1600 ppb for Phosphates at the pool store...i don't see any evidence of a problem with my IC-40 SWG.....and I always thought to ignore it.

As mknauss suggested...read the manual...I found this tidbit from the Pentair IC40 manual:

Nitrates and Phosphates can cause extremely high chlorine demands and will deplete chlorine from your swimming pool. In some cases nitrates may even lower your chlorine levels to zero. Your local pool professional can test for nitrates and phosphates. While a 0 ppm level of nitrates is the ideal, the pool owner should make sure that nitrates DO NOT exceed 10 ppm. Phosphates should not exceed
125 parts per billion (ppb).

SO...SHOULD IT REDUCE MY PHOSPHATES? Again, my pool has no trouble staying at or above 7 ppm (CYA around 70)....and in fact it was staying above 10 ppm FC up till about a month ago when I reduced run time and % on the IC-40.

And if the fill water is 179...I wonder where are the Phosphates coming from?

Thanks
MM
From Phosphate Dosing in Drinking Water Distribution Systems Promotes Changes in Biofilm Structure and Functional Genetic Diversity
Water utilities treat drinking water by adding phosphate to prevent metal dissolution from water pipe work systems and particularly lead poisoning.

As far as if you should remove - if the SWG is working fine then probably not something to worry about. If you're curious you could remove them from the pool and see if your efficiency goes up on the SWCG. If you do, use a quality remover like Orenda or SeaKlear. See:


Personally - I do treat once a year for phosphates, before I go on vacation. It's just a little insurance in case my FC dips too low, and I get a lot of organic stuff in my pool over the winter because my safety cover is a mesh cover. But that's a choice I make and is an optional thing in my mind.
 

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jark87

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Jun 5, 2011
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Flower Mound, TX
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Chlorine
Salt Water Generator
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Jandy Aquapure 1400
Personally - I do treat once a year for phosphates, before I go on vacation. It's just a little insurance in case my FC dips too low, and I get a lot of organic stuff in my pool over the winter because my safety cover is a mesh cover. But that's a choice I make and is an optional thing in my mind.
I do the exact same thing and am in a very similar situation - lots of organic material due to pool being surrounded by trees and a mesh winter cover. The only 2 times in 15 years that I’ve had algae blooms were when I wasn’t controlling phosphates. Both times I had FC levels of 5+, so I went back to phosphate control. The Orenda product is inexpensive and easy to use. However, the presence of phosphates never impacted my SWCG production.
 

Mdragger88

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Jun 1, 2018
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Fwiw- I dunno if I have any phosphates/nitrates or not - never ever tested for them. But I know I have plenty of fc so I sleep pretty well at night 😁
P.S. - Pentair also says to keep cya 30-50ppm & fc 2-4ppm max - this is an algae bloom waiting to happen with one high uv or heavy bather load day. Definitely Without adequate fc levels algae food becomes a factor because algae can be present. But nitrates/phosphates don’t directly consume fc. That’s a secondary consequence because there’s algae present.
Some manufacturer recommendations are based on outdated info just like the pool store. My spa manual also tells me to dump acidic chems in my skimmer 🚫
I don’t follow that advice either.
There’s some good info in this thread about the subject as well👇
 
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mmcwhorter

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Jul 13, 2015
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Huntingtown, MD
As to CYA metioned above, and this is what just works for me.....I put about 2 pounds CYA in 5-gallon bucket of water, and let it sit overnight. By morning...80% of the CYA it is dissolved into a milky liquid when I stir it up with a long-handled brush.... That pure liquid solution is what I pour into the skimmer....never have globs...there is some powdered residue at the bottom, I fill the bucket up a second time, stir and pour....and of course, I wait 2-3 days at least before a backwash. When I try the "sock in the skimmer" method, it seems to take literally weeks.
 

Sunnydaze

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Mar 8, 2021
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AZ
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As to CYA metioned above, and this is what just works for me.....I put about 2 pounds CYA in 5-gallon bucket of water, and let it sit overnight. By morning...80% of the CYA it is dissolved into a milky liquid when I stir it up with a long-handled brush.... That pure liquid solution is what I pour into the skimmer....never have globs...there is some powdered residue at the bottom, I fill the bucket up a second time, stir and pour....and of course, I wait 2-3 days at least before a backwash. When I try the "sock in the skimmer" method, it seems to take literally weeks.


All CYA must not be created equal. I can put 2 pounds in a sock and it will be gone within an hour if i squeeze it every 15-20 minutes. Perhaps warmer water helps.
 

mmcwhorter

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Jul 13, 2015
264
Huntingtown, MD
I have the same "lots of trees/mesh cover problem"...and never once have opened the pool in March to ANY algae...of course, the water gets down to 45-55 degrees most of the winter....and I also SLAM before the cover is installed.
 

IceShadow

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Count your blessings. I close after water is down to 60 F or less, raise to SLAM level, verify with OCLT that nothing is in the pool, let it come back down to normal, clean the pool so it is spotless, add Polyquat 60 for startup levels, put cover on, open before water hits 60 F - last two openings (when I was the one who closed) still had some algae in the spring. It cleaned up very quickly but I'm pretty sure there's not much else I could do.

For CYA, I dissolve in a mesh laundry bag in front of a return. It might take a day or so, with a little squeezing now and then, but it dissolves.
 

jark87

Silver Supporter
Jun 5, 2011
945
Flower Mound, TX
Pool Size
25500
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Jandy Aquapure 1400
All CYA must not be created equal. I can put 2 pounds in a sock and it will be gone within an hour if i squeeze it every 15-20 minutes. Perhaps warmer water helps.
I agree. I have the same issue as @mmcwhorter in that I can’t get it to dissolve using the sock method. I’ve been stirring in a bucket of hot water, but will try letting it sit overnight.

In terms of opening, I also SLAM prior to putting the cover on and I keep FC up all winter, but because I don’t brush at all during the winter due to the cover, my opening day results in a cloudy mess. Water chemistry will be fine and I don’t have algae, but lots of fine debris that sifted through the mesh cover will be on the bottom and it gets stirred up as I brush for the first time. I can usually have the water cleared up within 24 hours.
 

Mdragger88

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Jun 1, 2018
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I haven’t had any trouble with cya dissolving- I usually use the clorox brand from Walmart & recently got this one from the local ps - it did fine as well 👇
D1F70CF1-712E-4320-9B24-9F7F5D3339A5.jpeg
Takes me a couple hours for 2#’s or so.
Perhaps I’m an aggressive squeezer 🤷‍♀️

I close at slam level when the water is in the very low 60’s (late October) & open before it rises above the low 60’s (early April) - there’s always a bit of fc left (15ppm this year). For insurance I check it for temp & fc a couple times during the winter because we get crazy random heat waves sometimes. The Christmas day check fc was 17.5ppm.
I don’t use polyquat. I have a solid cover. Always been tfp clear upon opening.
 

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