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Thread: Why is my pH so high?

  1. #1
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    Why is my pH so high?

    We started up our pool last week with a clean fill of water from the mains (pH about 7.5), and the water is nice and clear. But the pH has been over 7.8 for the past three days since I added cal hypo, and doesn't seem to be coming down. We use trichlor tablets in an erosion feeder to chlorinate the pool, which ought to bring down pH. I've also used about 2 kg of dry acid in total added around the edge of the pool (not all at once, but over three days). Should I just keep going with the dry acid, or is something else going on? Probably I'm just being daft, but we had problems with constantly rising pH last year and it worries me.

    Test results this morning:

    FC=1.84
    TC=2.4
    CC=0.56
    pH=8.1
    TA=140
    CH= 280 (guessing based on fill water, will test properly next time)
    CYA=14 (calculated from amount of dichlor and trichlor used)

    Thanks.
    90k litres, outdoor in ground pool, concrete, painted (I hate paint)
    Sta-Rite 5P2R 1.5 Hp pump, undersized sand filter (needs upgrading).

  2. #2
    Senior Member solarboy's Avatar
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    Re: Why is my pH so high?

    Your TA seems high which would cause pH to rise. There's an article in Pool School on how to lower TA.
    pool-school/lowering%20total%20alkalinity
    Self built 5500 gallon bare concrete (temporarily) pool with limestone coping, Pentair Swimmey 1/2 HP pump, Triton sand filter with DE, Simpool peristaltic muriatic acid pump with pH sensor and Monarch SWG. Home made solar heater with Pentair Compool control panel and 3 way valve. 1 skimmer, 1 main drain, 2 returns, 2" plumbing, Hayward auto fill valve.

  3. #3
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    Re: Why is my pH so high?

    I don't see anything in your numbers or the info you posted that would cause your pH to go up.

    Meanwhile, what's FAR more important is that you get it down and start to control it. Use muriatic acid and bring it down to the mid 7's. Today is not too soon.

    You also need FC and CYA in your pool ASAP or your pool will not be nice and clear for too much longer.
    Dave S.
    Site Owner
    TFTestkits owner
    TFTestkits , PoolMath , Pool School

  4. #4
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    Re: Why is my pH so high?

    Thanks. So, it sounds like I should keep going with the dry acid then - muriatic acid is hard to get hold of in the UK. Actually most pool things seem to be hard to get hold of here. It's very frustrating.

    I did think my FC level was OK, a little on the low side, but not desperate. Pool calculator says aim for between 1 and 4 with this CYA level. Today is cloudy and nobody is swimming, so the chlorine shouldn't be going anywhere in a hurry.
    90k litres, outdoor in ground pool, concrete, painted (I hate paint)
    Sta-Rite 5P2R 1.5 Hp pump, undersized sand filter (needs upgrading).

  5. #5
    Senior Member ivyleager's Avatar
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    Re: Why is my pH so high?

    Quote Originally Posted by loop_pea
    Thanks. So, it sounds like I should keep going with the dry acid then - muriatic acid is hard to get hold of in the UK. Actually most pool things seem to be hard to get hold of here. It's very frustrating.

    I did think my FC level was OK, a little on the low side, but not desperate. Pool calculator says aim for between 1 and 4 with this CYA level. Today is cloudy and nobody is swimming, so the chlorine shouldn't be going anywhere in a hurry.
    True, but your CC (TC - FC = CC) is above 0.5, which generally is cause for shocking. Moreover, low FC AND high pH AND something possibly brewing = something will definitely brew. My experience anyway.
    CaryB
    36 x 18 IG vinyl, 25K, 1 HP pump, sand filter
    1 skimmer, 2 returns, no main drain
    Old school: PoolSolutions test kit

  6. #6
    Senior Member solarboy's Avatar
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    Re: Why is my pH so high?

    Quote Originally Posted by loop_pea
    Thanks. So, it sounds like I should keep going with the dry acid then - muriatic acid is hard to get hold of in the UK..
    You could try looking for Hydrochloric Acid, it's the same thing. Often used to clean up concrete mess from tiles etc, but make sure it doesn't have anything else in it.
    Self built 5500 gallon bare concrete (temporarily) pool with limestone coping, Pentair Swimmey 1/2 HP pump, Triton sand filter with DE, Simpool peristaltic muriatic acid pump with pH sensor and Monarch SWG. Home made solar heater with Pentair Compool control panel and 3 way valve. 1 skimmer, 1 main drain, 2 returns, 2" plumbing, Hayward auto fill valve.

  7. #7
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    Re: Why is my pH so high?

    Tested this lunchtime and the pH had come down to 7.9. I threw in the rest of the dry acid today, probably another 1kg, half at lunchtime, and the rest this evening, but the pool is still at 7.9. Hmm.

    I asked a pool guy to have a go at "scabbling" a small area of paint - probably about 1 m2. Instead he took a sander to it, exposing bare plaster. Could that have something to do with the pH going up?

    The pool is developing a sort of brown scum line - is this the result of the pH being high?

    I'd like to put something in the water to up the chlorine without increasing my CYA (or we won't make it to the end of the season), but from experience I think both bleach and cal hypo will send the pH skyrocketing again.
    90k litres, outdoor in ground pool, concrete, painted (I hate paint)
    Sta-Rite 5P2R 1.5 Hp pump, undersized sand filter (needs upgrading).

  8. #8
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    Re: Why is my pH so high?

    The pool is developing a sort of brown scum line - is this the result of the pH being high?
    It's probably from your lack of chlorine

    Once more, your CYA is too low. You should be at least at 30-40ppm.

    Your FC is too low. You should be up around 3-4ppm. Bleach will not permanently raise your pH.

    Get your pH down....further
    Get chlorine in your pool
    get CYA in your pool
    Dave S.
    Site Owner
    TFTestkits owner
    TFTestkits , PoolMath , Pool School

  9. #9
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    Re: Why is my pH so high?

    Well, I have brushed the walls, added more acid, FC is up to 3 and CYA is going in with the tablets. The weather forecast for the rest of the week is really poor, so I don't think the low CYA is going to be a problem.

    Looks like I need a lot more acid though.
    90k litres, outdoor in ground pool, concrete, painted (I hate paint)
    Sta-Rite 5P2R 1.5 Hp pump, undersized sand filter (needs upgrading).

  10. #10
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    Re: Why is my pH so high?

    I'm a couple of days further on. My FC this morning was 4.5 but my pH is still 7.9 and has not budged despite continuing acid additions.

    The only positive thing is that the brown scum line is fainter - I am wondering if that is due to metals as we have rusty handrail brackets putting iron in the water.
    90k litres, outdoor in ground pool, concrete, painted (I hate paint)
    Sta-Rite 5P2R 1.5 Hp pump, undersized sand filter (needs upgrading).

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