A few cholorine questions

[osie]

Hi All

I was wondering... which is what I do when it is too cold to do anything else.

1) What is the point of chlor choc... or what can it do that javel can not do.

I ask because I am going to open up the pool soon and wondered if adding choc will have any advantages or can I just go with  the javel.

edit: I should mention that no one will use the pool for several months and so I do not need to see any immediate changes.

2) As I understand CYA stops the chlorine being used up quickly... and CYA is in the gallets but not in javel.

So, is it the CYA in the gallets which stops the gallets being used up quickly or it is the CYA in the pool which stops chlorine being used up quickly.

or put another way, if I have CYA in the pool and add javel to the pool, will the CYA already in the pool stop the chlorine being used up quickly.

3)

My idea for this year is to add a few gallets each month to aid chlorine and provide CYA and add javel regularly to control the cl level.  Does this make sense.

Thanks

Osie

[chem geek]

1) Chlor choc is Trichlor and adds Cyanuric Acid (CYA) aka stabilizer or conditioner to the water.  For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases CYA by 6 ppm.  Chlor choc is quite acidic so needs pH Up or equivalent chemicals and it also lowers Total Alkalinity (TA) over time, though pH Up will raise that (i.e. compensate) as well.  Chlor choc dissolves slowly, usually a large puck lasting around 5 days or so in a floating feeder, so it's main advantage is dosing convenience.  It's disadvantage is primarily the buildup of CYA over time.

2) If you have CYA in the pool and add javel (chlorinating liquid or bleach) to the pool, the CYA already in the pool will help protect the chlorine from breakdown from the UV in sunlight.  So as you have surmised, you don't need to use Chlor choc and can use separate CYA and javel instead.  Since the CYA doesn't go away except by water dilution, once you are at the proper level then javel is the best choice though must be added regularly (usually every day or two in the summer).  To keep the pH more stable, when using javel you want a lower TA, usually no higher than 80 ppm.  TA is a source of pH rise due to carbon dioxide outgassing -- it essentially is a measure of the over-carbonation of the pool.

3) If you have some water dilution, such as from backwashing a sand filter, then you may not get too much CYA rise from using a few gallets each month.  Also, you can always increase your FC target level as the CYA level rises to keep the FC/CYA ratio constant.  If you keep the FC at least as high as 7.5% of the CYA level, then you should be able to prevent algae growth regardless of phosphate level and without the need for any additional algaecides.

[halfblind]

I am a little confused by your answer chem geek - not unusual.

You talk about chlor choc lasting about 5 days in a dispenser but I thought that the large gallets were slow release and that chlor choc came in either powder form or small quick dissolving tabs.

You can get slow release chlor without the "stabilizer" part - no little blue bits - would these still contain cyanuric acid ?

[osie]

Just to say thanks  for the great explanation... I may even get a trouble free pool this year (fingers crossed)

[Théière]

You are correct, our chlore Choc is granules or 20g pastilles usually put in the Skimmer for 24h dissolving. Larger galets are slow release all contain some CYA. The non CYA that you mentioned are calcium hypochlorite which just turn into mush so are not slow release either.

These will add to your already high calcium level so would be a bad move as a lot of France has hard water to start with

[halfblind]

[quote user="Théière"]You are correct, our chlore Choc is granules or 20g pastilles usually put in the Skimmer for 24h dissolving. Larger galets are slow release all contain some CYA. The non CYA that you mentioned are calcium hypochlorite which just turn into mush so are not slow release either.

These will add to your already high calcium level so would be a bad move as a lot of France has hard water to start with[/quote]

Thanks for that, so just stick to brico javel then ;)

[Théière]

I do [:)]

[chem geek]

I should have said that a "large puck" was about 200 grams and about 7-1/2 centimeters in diameter.  Sorry about that.  Also, if you see "little blue bits" in pucks, then that is not CYA.  It's probably something else like copper or some other additive.  Standard Trichlor is a white solid and the chlorine and CYA are not separate -- they are combined in a single chemical (i.e. the chlorine is attached to the CYA).