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Thread: Sequestrants and Phosphates...Is there a relationship?

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    Sequestrants and Phosphates...Is there a relationship?

    I have posted in the past about phosphates being introduced into a pool by adding sequestrants with phosphonates in them. So recently I've been noticing that some pools after being treated for phosphates, will leave iron stains behind. Usually they are very faint rusty colored areas left behind where the precipitate settled into piles. So I'm wondering if by treating phosphates, I'm getting rid of the sequestrant, and allowing the iron to oxidize and stain the liner. In other words, if I have a problem with iron in a pool, and I add sequestrant, am I working against myself to treat that pool for phosphates?
    TreeFiter

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    JasonLion's Avatar
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    Re: Sequestrants and Phosphates...Is there a relationship?

    Yes and no. Sequestrants are not affected by phosphate remover until they have broken down, long after they stop working as a sequestrant, so phosphate remover will not interfere with sequestrant.

    But the other way around is an issue. All of the effective sequestrants will add phosphates to the water, typically more quickly than they can be removed (without extreme measures). Since removing phosphates is nearly always a waste of time and money, this isn't normally a problem.

    Your iron deposits might be a reaction related to the clarifier in most phosphate removers, which can in some situations cause the sequestrant bound to metals to clump.
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    Mod Squad Bama Rambler's Avatar
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    Re: Sequestrants and Phosphates...Is there a relationship?

    There is no need to treat for phosphates in the first place, but if you want to know the answer why don't you test the sequestrant level before and after?
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    Re: Sequestrants and Phosphates...Is there a relationship?

    +1 what bama said. You are not doing your customers any favors using phosphate remover in the first place.
    Dave S.
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    Re: Sequestrants and Phosphates...Is there a relationship?

    I've been through this on other posts. If a pool has high phosphates, and I'm only there once a week to service the pool, there will be plenty of opportunities for FC levels to dip enough for algae to begin to grow and bloom. Yes, it is possible to keep algae under control in a pool with phosphates, but with service only once a week it is a pretty big gamble to take.

    I've never tested for sequestrant levels. What does this involve? What levels should be expected?
    TreeFiter

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    Re: Sequestrants and Phosphates...Is there a relationship?

    I've been through this on other posts
    Yeah, that's what I remembered. It doesn't seem to me like we would be a good resource for some technical nuance about phosphate removers when we are the ones who don't ever use them.
    Dave S.
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    Re: Sequestrants and Phosphates...Is there a relationship?

    Quote Originally Posted by TreeFiter

    I've never tested for sequestrant levels. What does this involve? What levels should be expected?

    It would depend on what the active is, and I don't know that when it comes to pool sequestrants. It could be easy and accurate, or elaborate and something you might have to go to HACH for. As for the required residuals, you'd have to consult the manufacturer on that. I know that some are phosphate-phosphonic acid based, and there are readily available tests for that, but it may well be something more expensive and time consuming than you want.

    I think Dave said it well. We are likely not your best source on this.
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