Too much cyanuric acid

[Mik from LA]

This is my third summer with a 50 cu m pool. The water is clear and ph, chlorine and alkalinity are in the normal range. However the cyanuric acid is reading high at 150 ppm. Should I be replacing a percentage of the water now or will the high level reduce over time?

[Chas]

My understanding with cyanuric acid is that once it's there it's there for good and the only way to reduce it is to dilute.  We change about 30% of the water at the end of each season and that seems to keep it in bounds.

[chrish]

Yes you need to cahange 30-50% of the water

chrish

[Mik from LA]

Thanks for the clear answers. Was hoping otherwise. Will get on with it right away so as not to waste this fantastic weather we are having.

 

[Poolguy]

The correct range for isocyanuric acid (stabiliser) in a pool water is 30-50ppm above that you will start to experience 'chlorine lock' whereas the chlorine may be at normal or even high levels but It cannot apply its effect on contaminants due to the Higher level of Cyanuric acid. Above about 150ppm then you virtually have no chlorineation at all.

Curiously, a similar effect can be shown below 10ppm as the effect of Cyanuric actually enhanced the presents of chlorine in the water, by making the molicules heavier. This also helps to spread the chlorine evenly thoughout the pool. So too little Cyanuric and the the more chlor you add it seems to leave just as quick.

I concur with Chris, empty half your pool and refill, but do that twice:- 150ppm /2 = 75ppm, 75/2 is 32.5ppm, I presume that you  are going to continue to dose with Acid Dichlorocynurate so you need som more room for the next round of gallets.

Alternatively you could change your water with a tarpoulin over the old water with a siphon  and add the new water above - that could be too much science however.

Andrew

[Mik from LA]

Thanks Andrew - the idea with the tarpaulin is brilliant. (except i have nearly completed the first half change :(   ). I understand the maths. I am not sure where the Acid Dichlorocynurate comes in. Is that the stabiliser in the slow chlorine tablets? If so then you mean when I add more tablets I add to the 32.5 ppm that I will be starting off with taking me into the correct range.

I normally adjust ph, then use shock chlorine to start with then, when the chlorine level comes down, put in the slow (stabilised) chlorine tablets to maintain the correct chlorine level. This has worked for me in the past. Is this correct?

[Poolguy]

correct

 

A+

[Jonzjob]

As Andrew knows when I changed the water in our pool I made up a curtain of polly sheet with the top floating on a 4.5 meter plank of wood and the bottom weighed down with a length of plastic tubing. It was anchored at both ends to stop it floating down the pool. The bottom of the sheet was almost touching the bottom of our even depth pool.

I took the water out of the far end of the pool using the cleaner vacuume suction with the curtain at the other end and fed the new water into the space between the curtain and the 'small end of the pool away form where it was being taken out. As the new water went in the curtain was moved slowly up the pool thus stopping the new mixing with the old. (blimey, I wish I had taken photos!!!)

Worked for us ad I even had to put some cyanuric back in because it had taken too much out!!

All 50 tubes now in place and working now Andrew![:D]

[Mik from LA]

Thanks again for all your help.

I only failed two "O" levels at school :- Chemistry and French.

I should have paid more attention