Green Pool

[Simon]

We have got a green pool.

Cyuranic Acid = 62pmm

Chlor = 7ppm

pH is low but we are adding pH+ to get it to 7.2.

Any ideas?  It looks like it's getting better but if it doesn't clear at pH 7.2 what should we do?

Many Thanks

[Théière]

Hi Simon,

Thanks for posting your figures, with CYA at 62 you need to achieve a much higher choc figure.  Don't purchase choc as it will add even more CYA which you don't need, use unscented Javel from a brico €18 for 20 litres and either some PH- or Hydrochloric acid from a Brico (careful of the fumes).

You need to raise the free chlorine to around 20ppm and hold that figure with regular javel additions until the green algae turns blue/grey. If you let us know size of your pool in m3 then I can give you an idea of quantities to add.

I would also stop adding PH+ as chlorine is more powerful at lower PH and th PH will rise when you add javel.

 

[Poolguy]

[quote user="Simon"]

We have got a green pool.

Cyuranic Acid = 62pmm

Chlor = 7ppm

pH is low but we are adding pH+ to get it to 7.2.

Any ideas?  It looks like it's getting better but if it doesn't clear at pH 7.2 what should we do?

Many Thanks

[/quote]

 

And so  what is the TAC....(if its not over 100 then its that which is to blame for the green and the low pH)  it rained a lot last night and so a lot of pools will start turning this morning.

Andrew

 

[Simon]

Hi

Latest readings (Monday) are

Chlor = 6ppm

TA = 110

pH = 7.2

CYS = 54

Pool is now almost clear and no green at all.

Should TA be higher?

Many Thanks

 

[Théière]

Hi Simon, Is your pool vinyl liner or concrete, plaster/tile?

If your PH stays pretty stable then that is the right amount for your pool figures are only a guide.

 

[Simon]

Theiere

The pool is a vinyl liner pool - 3 years old.

BR

[Théière]

Simon that level should be fine then, PH fluctuations are usually the clue to incorrect TA. On some forums people add PH+ to their salt systems which is weird as producing chlorine and off gassing of Co2 will raise the PH anyway so PH- would be the correct call if their TA was correct.

With your level of CYA you need to run your pool at 4ppm free chlorine to ensure you stay clean and clear of algae etc. Don't panic as the bulk of your free chlorine is bound to the CYA so you only have 1-1.5 ppm of free active chlorine in reality.

[chem geek]

6 ppm Free Chlorine (FC) with 54 ppm Cyanuric Acid (CYA) has the same active chlorine (hypochlorous acid) concentration as a pool with 0.1 ppm FC and no CYA, not 1-1.5 ppm FC.  In this pool, over 98% of the chlorine is bound to CYA.  This not only comes from the core science known since at least 1974 in the [url=http://richardfalk.home.comcast.net/~richardfalk/pool/OBrien.htm]O'Brien paper[/url] that determined the equilibrium constants, but it's also consistent with the lowering of kill times for bacteria, inactivation of viruses and protozoan oocysts, rate of oxidation of organics, and lowering of ORP levels as well as algae inhibition rates (from the experience of tens of thousands of pool owners; not from the one scientific paper on this).  This is all documented in [url=http://www.troublefreepool.com/certified-pool-operator-cpo-training-what-is-not-taught-t18432.html]this post[/url] in the "Chlorine/CYA Relationship" section.  Fortunately, it takes very low levels of active chlorine to kill most pathogens and somewhat more to prevent algae growth (such levels being in the [url=http://www.troublefreepool.com/pool-school/chlorine_cya_chart_shock]Chlorine / CYA Chart[/url]).

Richard

[Théière]

Thanks Richard,

I was using your 7.5% of CYA figure which seems to work for pools around here. We don't seem to need to go as high as you guys in the states in most cases. I have been maintaining my pool on 0.2ppm (with obvious fluctuations during the day) without CYA (using ACO) very satisfactorily so far. When I mentioned 1-1.5ppm this was made an assumption of 75% of the chlorine being bound to CYA hence 1ppm of chlorine available I did not bother as I do not have a copy of the graph allowing me to note the exact hypochlorous acid figure for equivalent amounts.

Note to Simon:

I would be interested to know your chlorine consumption (test in the morning and evening) per day in strong sunlight to compare with my own, preferably on a day without bathers in your pool if that is possible.

[Simon]

I will not be able to test as I am currently in the UK, but will test and keep a record when I am there again in August.

Many thanks for all your help.  According to the Pool Cleaner the Chlor is still quite high and he didn't get a proper reading as he didn't dilute the sample, but the pool is now clear and clean.

BR 

[Théière]

Thanks Simon.