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Thread: Backflow into main water supply?

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    Join Date
    Apr 2015
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    Charlotte, NC
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    Question Backflow into main water supply?

    Our pool was finished only a few weeks ago. It's an inground, and because we had an existing irrigation system, the installers hooked an auto-filler into the irrigation system plumbing.

    The irrigation system does have an RPZ (a Febco 860U, I believe) installed.

    Lately, we've all noticed a pretty strong smell of chlorine in our drinking water. You can smell it while taking a shower. This is a new phenomenon in our house.

    Is it possible that pool water is backflowing into our main pipes, into our drinking water?
    10,000-gallon inground pool, Jet Black PebbleTec / plaster
    Hayward S244S Sand Filter
    Hayward Super Pump, 2 HP
    Hayward AquaRite AQR9 / T-CELL-9 ECG
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    JasonLion's Avatar
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    Re: Backflow into main water supply?

    While it is remotely conceivable that pool water could somehow get back into the drinking water, it is extremely unlikely. The RPZ would have to be seriously broken and the household water supply would have to have completely lost pressure. Neither of those is likely, and both happening at the same time is very very unlikely.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Mod Squad YippeeSkippy's Avatar
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    Re: Backflow into main water supply?

    I'd test the tap water with my pool test kit (TF-100) to see what the chlorine amount is. Then I'd call up the public utilities/water department there in Charlotte and talk to them about it. I know the head of the Mathews department if you were there?
    Other wise I don't see how an autofil could do what you're suggesting?
    My Amazon Smile for November12K Fiberglass IG, Infinity 4000 automatic cover, SWCG, Hayward Sand Filter, Hayward 1.5 Pump, Doheny Discovery Robot, Savi Melody LED pool lights, outdoor speakers and other assorted doo-dads. Sundance Altamar Hot Tub.
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    Re: Backflow into main water supply?

    My wife suggested testing the water coming from the tap. I thought that was ridiculous, since I assumed that the chlorine level would have to be sky-high (by potable water standards) to be measurable.

    Well, I decided to give it a try.

    My Clorox test strips told me that the FC in our tap water was at roughly 2 ppm. Two separate tests with my Taylor K-2006 told me 1.5 ppm FC.

    I'm not sure what the maximum chlorine level should be in potable water. Some sources I'm finding say it can be as high as 4 ppm (that sounds really high to me though). I'm really concerned now.

    I think I will visit a neighbor tomorrow and test their water to see if this is just us or if it's a wider issue.
    10,000-gallon inground pool, Jet Black PebbleTec / plaster
    Hayward S244S Sand Filter
    Hayward Super Pump, 2 HP
    Hayward AquaRite AQR9 / T-CELL-9 ECG
    Polaris 360

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    JasonLion's Avatar
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    Re: Backflow into main water supply?

    2 ppm is a very very common FC level for drinking water in the US and is considered safe and reasonable by the EPA.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Backflow into main water supply?

    Quote Originally Posted by JasonLion View Post
    While it is remotely conceivable that pool water could somehow get back into the drinking water, it is extremely unlikely. The RPZ would have to be seriously broken and the household water supply would have to have completely lost pressure. Neither of those is likely, and both happening at the same time is very very unlikely.
    This makes a lot of sense. Thank you. We have not noticed any loss of water pressure.

    Quote Originally Posted by JasonLion View Post
    2 ppm is a very very common FC level for drinking water in the US and is considered safe and reasonable by the EPA.
    Maybe they just tweaked our water supply then?
    10,000-gallon inground pool, Jet Black PebbleTec / plaster
    Hayward S244S Sand Filter
    Hayward Super Pump, 2 HP
    Hayward AquaRite AQR9 / T-CELL-9 ECG
    Polaris 360

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