Pool water PH unstable + Not holding chrloine!

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Terribly Inept

Pool water PH unstable + Not holding chrloine!

Postby Terribly Inept » Sun 24 Sep, 2017 02:18

Hi all, hopefully someone can help me as I am utterly bemused by what is going on with my pool chemistry.
My pool is 10,000 galleons. I use a palintest Pooltest 3 to read my pools levels, I use the manufacturer supplied reagents.

Around a month ago my pool had a free chlorine level of around 6ppm, way too high for an indoor pool. I left it open to the sun for a few days without any chlorine treatment and have had on going problems since then.

My pool no longer holds free chlorine. I've been using a multifuncation chlorine tablet that also contains an algaecide and a flocculant (200g, contains Trichloroisocyanuric Acid).
My chlorine level has been 'stable' at about 0.28 ppm. I have tried adding stabilized chlorine granules, in addition to the tablets and also Sodium Hypochlorite 14/15% (Liquid Chlorine). None of these have had any effect at raising the free chlorine levels in the pool. It stays at an avarage .20 ppm - .40ppm.

The pools Ph was low at 7.0. Over the last week I had been slowly raising raising the pH. Yesterday night it was a 7.5

Went to test the free chlorine and Ph levels today. My meter is reading a free chlorine level of 0.28ppm and a PH of less than 6.5. (just reads (<6.5).

How the heck did my pH level go from 7.5 to <6.5 OVERNIGHT? and why is my pool not holding free chlorine?

I last shocked the pool around 2 weeks ago.

Please help I have absolutely no idea what the problem is here.

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Re: Pool water PH unstable + Not holding chrloine!

Postby maiphuonganh » Wed 21 Feb, 2018 23:26

To increase the pH you need to stop adding chlorine tablets (trichloroisocyanuric acid)
Decreasing the free chlorine level is normal, the amount of free chlorine used to kill bacteria in addition to it can be lost in the sun.
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Re: Pool water PH unstable + Not holding chrloine!

Postby Denniswiseman » Thu 22 Feb, 2018 03:00

Do You test for CYA, when you have excessive CYA it makes your chlorine ineffective and increases your acid use thus reducing your pH
To reduce your CYA partial drain and refill, an indoor pool needs only 20ppm CYA
Aerate your water to raise pH
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

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