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Thread: Phosphates & Gunite?

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    Phosphates & Gunite?

    Has anyone else had a Gunite Pool to have high phosphates (Gunite is at least 20yrs old and it's old and chipping away).

    Could the old gunite be CAUSING the phosphates?

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    JasonLion's Avatar
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    Re: Phosphates & Gunite?

    Welcome to TFP!

    Phosphates and gunite have nothing to do with each other. High phosphate readings are neither caused by gunite, nor do they pose any risk to gunite.

    For that matter, phosphates are completely irrelevant if you maintain appropriate FC levels. My phosphate level has been well over 4,000, though it is a bit lower now, and I never have any problems.

    Mostly phosphates are a way for pool stores to sell you expensive chemicals that you don't need.
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    Mod Squad Bama Rambler's Avatar
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    Re: Phosphates & Gunite?

    IIRC Chem Geek has had high phosphate with a plaster pool. Wherever the phosphates came from, they're a non-issue. They're not something you need to worry about, or do anything about.
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    Re: Phosphates & Gunite?

    I run a pool store and we definitely have problems with phosphates and pools here in southeast Georgia having a zero chlorine reading. We have to use Phosphate Remover by sea-klear often. Once the product is used they are able to regain a chlorine reading. I'm not understanding why you would think that the phosphates are a non-issue, that's the most ridiculous thing i've heard. Maybe it is different in different areas?? I'm not sure about that I was just curious to know about the gunite. I have one customer who has 20 year old gunite that's chipping away (whom refuses to get it fixed) and he has a major phosphate problem eating away at his chlorine. We've gotten his level down and he now is getting chlorine in his pool again. Like I said, I am just curious to where it can keep coming from.

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    bobodaclown's Avatar
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    Re: Phosphates & Gunite?

    Phosphates feed algae (its the algae that is using the chlorine), chlorine kills algae (sounds like he needs more liquid chlorine), kill the algae - no problem with phosphates. Chlorine is much more cost effective than phosphate remover. (The goal is to kill algae and keep the pool sanitized.) The boards here recommend FC levels being determined by CYA level, but not let CYA level get above 100, CYA is added with pucks, some CYA is recommended, and it is a higher level with a SWCG.

    Here's some reading: pool-school/pool_water_chemistry
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    Re: Phosphates & Gunite?

    There isn't any algae in the pool. It's crystal clear. His PH, Alkalinity, Calcium Hardness, Cyanuric levels are all in perfect range.

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    Re: Phosphates & Gunite?

    And also, he has used plenty of liquid chlorine. NO chlorine reading--- due to PHOSPHATES in his water. The lower the phosphate reading, the higher the chlorine reading

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    Re: Phosphates & Gunite?

    diversified,

    read "The ABC's of Pool Water Chemistry" up in Pool School...particularly about phosphates.....you are operating under a misconception.

    They are completely irrelevant in a properly managed pool.
    Dave S.
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    Re: Phosphates & Gunite?

    Quote Originally Posted by diversifiedservices
    And also, he has used plenty of liquid chlorine. NO chlorine reading--- due to PHOSPHATES in his water. The lower the phosphate reading, the higher the chlorine reading
    When algae is first growing, it may not yet be visible and this creates a chlorine demand with no visible algae. That is what you are seeing. I've had over 3000 ppb phosphates in my pool (there are many others with thousands of ppb phosphates) and we have one pool owner on this forum with over tens of thousands of ppb phosphates yet algae is kept from growing by maintaining a proper Free Chlorine (FC) level relative to the Cyanuric Acid (CYA) level.

    Phosphates and nitrates are food for algae, but algae are also limited in their growth by sunlight and temperature. So even under ideal conditions with plenty of algae nutrients in the pool, algae can only grow so quickly (roughly doubling in population every 3 to 8 hours). If you have a sufficient FC/CYA ratio (for manually dosed pools that's roughly an FC that is a minimum of 7.5% of the CYA level), then the chlorine kills the algae faster than it can grow so the algae nutrients (phosphates and nitrates) are irrelevant.

    In the pools you are talking about, there is already nascent algae growth so one must shock the pool by elevating the FC to a higher level to kill off the algae faster since there is more of it. However, if the CYA level is very high, then it is better to do a partial drain/refill of the pool to lower the CYA level since raising the FC to 40% of the CYA level can be impractical when the CYA level is high. Also, one does not simply dump some chlorine in the pool and hope for the best. To shock the pool, one MAINTAINS a high chlorine level and that means having a proper FAS-DPD chlorine test kit that can measure accurately up to 50 ppm FC. All of this is described in the Pool School.

    Most likely, some of the pools you are talking about are using Trichlor tabs and this increases the CYA level over time making the chlorine less effective unless you proportionally raise the FC level. Otherwise, algae will start to grow and show up as chlorine demand making it harder to maintain a chlorine level. This happened in my own pool 9 years ago when I was using Trichlor -- at some point, I couldn't keep up feeding enough Trichlor pucks to maintain an FC level. The following are chemical facts independent of concentration of product or of pool size:

    For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
    For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
    For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

    If the pool has a saltwater chlorine generator (SWG), then if there is a lot of calcium and phosphate in the water then one can get calcium phosphate scaling in the SWG cell though there are other ways of minimizing that including using 50 ppm Borates as an additional pH buffer. Scaling in the SWG cell can lower its output.

    Phosphate removers are like other pool store products of algaecides, clarifiers, flocculants, enzymes, etc. that are higher margin products that add additional revenue beyond the usually lower margin chlorinating liquid or Trichlor pucks. These extra products are not needed and most of the nearly 50,000 members of this forum and probably many of the over 400,000 visitors to this site during the summer months do not use such products and instead maintain their pools by following the Chlorine / CYA Chart and other practices described in the Pool School.
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    Re: Phosphates & Gunite?

    Quote Originally Posted by diversifiedservices
    Has anyone else had a Gunite Pool to have high phosphates (Gunite is at least 20yrs old and it's old and chipping away).

    Could the old gunite be CAUSING the phosphates?
    My gunite pool is extremely old (1957), and hasn't been replastered since 1989. I have no algae problem. And no, phosphates in Texas are not different than they are in Georgia.

    Are you sure it's not the plaster chipping away, and not the gunite?
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    Re: Phosphates & Gunite?

    Moved to "agree to disagree". I think diversified's mind will not be changed but I will leave the thread open for a while.
    Dave S.
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    JasonLion's Avatar
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    Re: Phosphates & Gunite?

    Quote Originally Posted by diversifiedservices
    I'm not understanding why you would think that the phosphates are a non-issue, that's the most ridiculous thing i've heard.
    My phosphate level is currently around 2,200. Two years ago it was over 4,000. Yet haven't had a problem with algae in many years.
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