CYA (Cyanuric Acid) build up in SPA water Problem SOLVED

[Magicman71]

We use our SPA every other day and we use Chlorine and keep a close eye on the water health. Noticing our test strips were testing high for Cyanuric acid (CYA) and the PH kept going very acidic (dark brown off the scale, this is a good sign of CYA overdose), we constantly had to add alkaline everyday but only really reducing the alkaline small amounts.

The chlorine remained high even with not adding it for a several days as though the CYA was keeping hold of it in the water.

We discovered the stabiliser part of most of the chlorine tablets/ powders is CYA and the tub was overdosed with it causing all readings to go out. I beleive this is fine in conditions where your hot tub cover is mostly off in sunny areas as this burns off, but in our case where we have to put the cover on after use as it's cold in England generally we found this issue.

 

We replaced half the water and switched our chlorine tablets with a liquid that contains no CYA (this is hard to find, and you MUST read the ingrediants as there's products out there that claim its free of CYA but when reading the ingrediants it not). After using the liquid the levels went back immediately and have been perfect ever since.. we’ve been able to put less chlorine in and hardly adjusted the Ph, and it stays balanced with less foam. 

 we believe that the CYA will burn off if its exposed to UV over time but this case as we have to put the cover on regulaly so there's no way for it to escape or lower.

I hope this helps some people.

[waterbear]

Let me see if I can clear up some of the misinformation in this post

19 hours ago, Magicman71 said:

. Noticing our test strips were testing high for Cyanuric acid (CYA) and the PH kept going very acidic (dark brown off the scale, this is a good sign of CYA overdose), we constantly had to add alkaline everyday but only really reducing the alkaline small amounts.

You have been uusing trichlor in your tub which is not recommended by most manufacturers since it is extremely acidic and it's hard to maintain pH befcause of the small volume of water in the tub. Low pH has nothing to do with high CYA levels. TA should be 100 to 150 ppm IN POOLS that use triclor to help maintain the pH. In tubs it's a recipie for disaster, IMHO.

19 hours ago, Magicman71 said:

The chlorine remained high even with not adding it for a several days as though the CYA was keeping hold of it in the water.

This is the purpose of CYA, it is a chlorine stabilizer and it protects chlorine from UV light. It does not 'burn off in the sun. It prevents the chlorine from burning off.

19 hours ago, Magicman71 said:

We replaced half the water and switched our chlorine tablets with a liquid that contains no CYA (this is hard to find, and you MUST read the ingrediants as there's products out there that claim its free of CYA but when reading the ingrediants it not). After using the liquid the levels went back immediately and have been perfect ever since.. we’ve been able to put less chlorine in and hardly adjusted the Ph, and it stays balanced with less foam.

There are 4 types of chlorine used in pools and tubs. 2 are stabilized (chemicals with the chlorine chemically bound to CYA (cyanuric acid) and are the chlorinated isocyanurates commonly known as trichlor and dichlor. 

Trichlor is an extremely acidic slow dissolving form of chlorine that is used in feeders or floaters in the form of tablets and will add 6 ppm CYA for every 10 ppm of chlorine added. Because of its very low pH it is not normally recommended for tubs because it is very difficult to buffer its effect on pH in the small volume of water.

Dichlor is a fast dissolving powder that is often used in hot tubs. It is mildly acidic but will add 9 ppm CYA for every 10 ppm FC added.

The two unstabilized (inorganic) chlorine sources are calcium hypochlorite and sodum hypochlorite,. Both are basically pH neutral (alkaline on addition, acidic on sanitation). Calcium hypochlorite is a slow dissolving powder that is usually used as a pool shock. It will add 7 ppm calcium hardness for ever 10 ppm FC added. This is only concern when you have very hard fill water. It is also used as a bleaching powder for household use.

Sodium Hypochlorite, also knows as Javelle water, is a liquid that is most often used a a pool and spa chlorine source and shock. It is also used as household laundry bleach. The only thing it adds to the water is a bit of salt when it breaks down and is, IMHO, the least problematic form of chlorine to use.

With that being said, CYA is still needed in a controlled amount since it will prevent the chlorine burning off if the spa is exposed to sunlight (20 to 30 minutes is all it takes to destroy most of the chlorine in a pool or spa with no CYA), it makes the sanitation efficiency of the chlorine less pH dependent, and it acts as a buffer  to make the chlorine less aggressive to swim suits and skin. For pools 30 to 50 ppm is the range, for spas 20 to 30 is sufficient. For salt water chlorine generators most manufacturers recommend somewhere between 50 and 100 ppm with most specifying around 80 ppm .

19 hours ago, Magicman71 said:

we believe that the CYA will burn off if its exposed to UV over time but this case as we have to put the cover on regulaly so there's no way for it to escape or lower.

No, it does not burn off over time nor escape. The only way to lower CYA is to drain some water and replace it with water that does not contain CYA. (There are some other ways to reduce CYA but they are not dependable such as  precipitating it as melamine cyanurate by adding melamine but this will cloud the water and clog the filter and there is bacterial degradation of CYA that occurs under certain condition but it is a slow process that usually occurs in pools that have been closed for the winter.)

I hope this clears up some of the confusion.