Vanishing Chlorine

Chlorinating, maintaining the right chlorine levels,
chlorine problems. Dichlor, trichlor, cal hypo, bleach,
granules, chlorine pucks and chlorine sticks.
Witzend
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Posts: 1
Joined: Tue 27 Apr, 2021 11:11
My Pool: 11 x 5 metre mosaic tiled pool, sand filter

Vanishing Chlorine

Postby Witzend » Tue 27 Apr, 2021 11:41

Hi, hoping someone can give me an idea on what the problem(s) might be.
I inherited a pool, 11 x 5 metre mosaic tiled, sand filter etc.
It was extremely green, this was last summer, the pump had packed up, and, as it is surrounded by olive trees, was full of olives, olive leaves and other debris.
Managed to clear the water over a week or so and fish out a fair few kilo's of olives!!
Struggled last summer to keep water crystal clear and to hold chlorine.
Maintained it over this winter so no massive build up of olives etc but, still cannot get it to hold / show chlorine.
It was also beginning to go green end of last week.
Put in an anti algae product, waited 48 hours then shocked, water now nice and clear.
I had been using multi function blocs up till recently, have now switched to liquid chlor, same results, no / very low chlor.
Yesterday I decided to try a super shock on it, that included shock granules and a dose of 3 litres liquid chlor.
pH has dropped from 7.5 to 7.1 and free chlor was showing 0.2. Around the same as before. T/C had been 0.5 before the shock.
I know the Cya is high at 80 but surprised it is having such an impact?
Thinking only solution is to start again, change filter sand and water. Pump was brand new last year and flow is good. Not sure how old sand is.
Pool is in the South of France.
Any thoughts on this??
Many thanks in anticipation


Denniswiseman
Pool Industry Leader
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Posts: 2592
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Vanishing Chlorine

Postby Denniswiseman » Tue 27 Apr, 2021 15:27

You will need to Slam (Shock Level and Maintain)
Let's have your numbers (CYA is very important)
FC:
TC:
pH:
TA:
CH:
CYA:
Chlorine / CYA Chart

Use these common products to balance your pool
Liquid chlorine (sodium hypochlorite or plain bleach)
Muriatic acid (hydrochloric acid) to lower pH and TA
Bicarbonate of soda to raise TA
Aeration will raise pH only
Soda ash will raise pH and TA

Test strips are commonly called guess strips
You really need to get yourself a decent FAS/DPD test kit (Taylor K2006c or TF Testkits TF100 in the states) to get accurate results as maintaining an appropiate shock level means testing quite often during the day
Teapot
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Posts: 1337
Joined: Tue 17 Oct, 2017 10:52
My Pool: 12 x 24 (45m3) liner pool, Triton TR60 filter with AFM glass media (Activate) and variable speed pump running 0.08HP
Location: UK

Re: Vanishing Chlorine

Postby Teapot » Tue 27 Apr, 2021 15:55

Witzend wrote:
I know the Cya is high at 80 but surprised it is having such an impact?
Thinking only solution is to start again, change filter sand and water. Pump was brand new last year and flow is good. Not sure how old sand is.
Pool is in the South of France.
Any thoughts on this??
Many thanks in anticipation

I am not surprised the CYA is having such an impact it is the most important chemical in your pool. No point in changing the filter sand as the "new sand" will be at least 65million years old. That doesn't mean it should should not give it a really good clean. Domestic filters do not backwash well so silt will build up over time.
Far better to ask you how you are measuring CYA and to use a phosphate remover. This can cloud the water for a bit but is all good long term.

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