Superchlorination

[Pko]

A question regarding Superchlorination.

I want to get rid of the combined chlorine in my pool ,30 M2, and I have read that I can do this by adding

10 times more chlorine than the amount of combined chlorine.

So my free chlorine was 1.0 and the total chorine was 1.5 ppm, giving a combined chlorine of 0.5 ppm

I added 2 liters of bleach 9.6% which is a total of 6 ppm chlorine if my calculations are correct.

But the day after my free chorine was 4.3 ppm and the total 5.2 ppm, so the combined chlorine was increased

to 0.9 ppm !

Did the same again, adding 3 liters of bleach, but again my combined chlorine has increased.

Am I doing something wrong, or can you not superchlorinate with bleach, or have I still added

too little perhaps ?

Would very much appreciate some guidance, thanks in advance,

paul&carin

[Théière]

Super chlorination (choc) is not the application of a dose of chlorine (any form) it is raising the free chlorine level and holding it at that level by regular additions. Although your figures were not bad (any amount of combined chlorine between 0-0.5ppm is ok) the reason the combined figures rise is that so much chlorine is in the pool it is oxidising everything out of the water even some cyanuric acid (CYA). You need to continue with regular additions for a bit longer until the combined chlorine level falls, if it rains your figures will go heywire for a while. Using bleach is fine as it mixes faster than granulated so gets to work quicker.

Do you have any other figures eg CYA T/A

 

[Poolguy]

Adding to my erstwhile colleague - your pool is a 'public pool' under the definition of the Direction de la Santé Public (formally DDASS) as I am sure you know. Your max level of  Combined Chlor may be no more than 0.6ppm to get through Control Sanitaire des Eaux de Piscine without a mention.

So Chocking once is really not the fix you need, as the problem will return after a time. As you know one of the great troubles in pool water is the existence of Ammonia which, when combining with Chlor produces Mono-chloramines and the rest hence raising the Combine Clhor level.

So if you change your sand to Zeolite it will go a long way to eliminate the Ammonia along with just about everything else bigger than 1 micron in the pool to alleviate this problem on continuing basis. It’s only the Conductivity that you will have to worry about after that.

Regards

Andrew

[Pko]

Thank you Théière,

because I use an electrolysolateur My CYA is very low, only 6 ppm.

My T/A is low, below mesuring range.

But My pH is good, 7.33, and very stable, it has not fluctuated more then a tenth in two months.

[Théière]

Although the official line is T/A 70-90 it is used to buffer the PH so if yours is stable that's fine. It maybe because your chlorine is actually being burned off by the sun's U.V. that the chlorine isn't around long enough to actually effect the PH overall.

Your CYA is not doing anything to protect your precious chlorine from the sunlight so that means your chlorine generator is running longer than normal to try and keep up. That is consuming more electricity than needed and as the actual cell with the titanium plates has a finite life cycle that too will have its life shortened by producing more and more chlorine and replacement cells are not cheap. Increasing your CYA to 30-50 will protect your chlorine for very little money although you would need to run the free chlorine slightly higher at 2.25ppm (30ppm CYA) to 3.75ppm (50ppm). You won't use anymore chlorine, you should use less, just having the level higher but will protect the chlorine from the sun's U.V.

 

[Pko]

yes, I have started this week using the chlorinetablets which contain the stabiliser to get some CYA in my pool, that's why my CYA is now 6 ppm where as a week ago it was zero. Will keep this up intill I reach 30 ppm.

But to get rid of the combined chlorine I need to keep on adding more chlorine extra, maybe even 3-5 lters of javel 9.6% in one go, is this correct ?

Must say that I'm a bit sorry I started with the superchlorination, because the combined level was only 0.5 ppm after having the pool in use for two months and the water has been christalclear, and still is, all that time. Just wanted to do it right and avoid problems later.

Thanks again for your input, Théière

[Théière]

Assuming you have about 4ppm free chlorine then 2 litres addition will take you to around 10ppm. As you have very little CYA then you have a very large amount of sodium hypochrite ion which is the really active portion of chlorine so it should not take very long to oxidise everything out. Adding chlorine after the sun has gone down in the evening will prevent losses to U.V.

It's all part of the learning curve [:)]

Let the level return to normal and you should be fine to re-test.

[Pko]

Thanks again for the info, Théière, after adding the javel once more and waiting for two days my combined chlorine is now back to 0.2 ppm.

[Théière]

Good stuff, makes a change to have some one who measures their pool properly.