High Phosphate Levels

by Jennifer

My pool guy is treating my pool for high levels of phosphate and beginning black algae (YUCK).

My pool guy has treated the pool for the phosphates but will treat the black/brown algae wednesday. He is not around today (sunday 7/24)

My question... do we clean the filter now or do we wait until it is treated for the algae and clean it then?

Thanks for your help

Jen :)

Thanks for the question Jennifer

First I'd like your to read these posts before your "pool guy" puts any more phosphate remover:

Swimming Pool Phosphate Level Over 1000

High Phosphate Levels And Low Chlorine Issue...

And especially this one:

High Phosphates Over 1000 & Cloudy Water

Be sure the pool guy has determined that you do in fact have black algae. Put a chlorine tab in a sock and place it on the spot. If it fades, it's algae.

Black Algae

If it doesn't fade, put ascorbic acid (Vitamin C) in a sock and place that on the spot. If it fades it's a mineral stain and should be treated as such, with an ascorbic acid treatment.

I'm not sure what is meant by "clean the filter". What kind of filter is it? By the tone of the question I would assume it's either DE or cartridge. You always want to have a clean filter regardless of what's going on.

Be sure he does the tests above so you're not wasting time and money. Look over the above posts about phosphate removers so you'll know what they do and don't do.

Hope this helps and have a great Summer. Let me know how it turns out for you.


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Phosphate Question. What Range Should It Be?

by Rosa

The phosphate on my pool is 95 and the Leslie's pool shop lady told me that has to be around 300.

My question is what is the right range?

Thanks for the question Rosa

First we need to establish what phosphates are. Phosphates are nutrients to help increase algae growth. The makers of phosphate remover products say the maximum level should be 125 ppb (parts per billion).

Most of the time pool owners get phosphates in scale and stain removal products. They're used for lifting stains, pool startups, and scale control. Many of these products contain phosphonic acid.

I have seen no evidence to support an increase in algae growth rates in swimming pool water that have phosphates below 1000 ppb. And I had a pool route in Arizona for years and was the pool operator for the YMCA in Albany, OR.

If you keep your chlorine between 1.5 - 3.5 ppm and the CYA between 30 - 50 ppm, and everything else in line, there's no need to use a phosphate remover. Phosphates are alright to swim in. The chlorine kills the algae, so if there's no algae, then why worry about phosphates? There is no correct range to keep phosphates. It can be 30 or 1000 ppb. It's not like your normal chemical readings.

Check back to this post for updates or answers.

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Hope this helps and have a great Summer.


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High Pool Phosphates

by Vicki

When they opened my pool, I got a call from the company that phosphates were "over the roof". Recommended a phos remover, bought a product called "Nix" lowered phos to 1/2 (700 ppm) She had us buy another bottle ($40/ea) and put that in and said to add 3# shock-water still not clear and my fiberglass steps are now "yellow-brown" I don't understand??? Pool is 10,000 gal. and don't know where to get advise. Was told that phos will kill chlorine??? HELP

Hi Vicki. I need your complete chemical readings, the actual numbers:

Chlorine, CYA (cyanuric acid/stabilizer), pH, Alkalinity, Calcium Hardness, and Metals (iron and copper) and names of any algaecides you may have used along with clarifiers, and/or flocs. It makes troubleshooting much easier and the process of clearing up your pool will go much faster.

We need to understand what phosphates are. They're food for algae, but not the only source. That can include nitrites and nitrates. Phosphates are fine to swim in, even at high levels such as 1000 or over.

Phosphates DO NOT eat up chlorine. Chlorine is the sanitizer for your pool and it's chemically impossible for phosphates to eat up chlorine. I'll also enclose a YouTube video I did about this very issue.


3 lbs. of chlorine in your water is way too much. 1 lb. of chlorine will increase the FC 10ppm per 10k gallons. That's the baseline. You used 3 lbs. so your FC will probably be close to 30ppm.

You're going to need to keep filtering 24/7 and backwashing until the phosphate remover is gone.

Get back to me with your readings and we can go from there. And don't put any more chemicals in the pool until then. You just might be wasting more money.


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