Cyanuric Acid Hot Tub

There is much debate on the topic if cyanuric acid needs to be used in hot tubs/spas. There are several studies that strike out the need for Cyanuric Acid in hot tubs. The CDC clearly recommends not using cyanuric acid or chlorine products containing cyanuric acid in hot tubs. However, there are hot tub owners who still widely use the product. This leads to a buildup of the product over time resulting in premature draining and refilling. All this makes the maintenance of the hot tub a hectic task leading to wastage of time and money. In this article let us see more into the details of the same.

Cyanuric Acid/ CYA

First of all, let us see what cyanuric acid is and why it is used. Cyanuric acid (CYA) is a stabilizer or conditioner which is used in pools and spas exposed to the sun so as to reduce the rate of decomposition of available chlorine by the harsh UV rays in the sunlight.

It was in the 1950s when the chemical was first introduced in the pool industry. During those times pools were chlorinated with sodium hypochlorite or calcium hypochlorite. These chlorine compounds came in powdered form. They were used in the form of liquid chlorine to serve the purpose of chlorination.  However, there was a problem associated with the process. UV rays of the sun caused degradation of the chlorine. In about four hours, the entire chlorine added to water can be lost to sunlight.  As a result, the chlorine added to the pools was not sufficient to keep the pool free from germs. This resulted in addition of chlorine to the pool water more than one or two times a day.

What cyanuric acid does is that it can improve the situation by keeping the chlorine in the water for prolonged periods (approximately eight times longer). And thus the situation got better. Pools that needed daily chlorination or even double chlorination in a day can last up to a week before the need for the next chlorination.  There was a boom in the industry with manufacturers combining chlorine with cyanuric acid resulting in the creation of a new set of products such as dichlor and trichlor which are chemically chlorinated isocyanurates. These products invaded the swimming pool industry at a quick pace.

Cyanuric Acid Buildup

So we can see that cyanuric acid was capable of stabilizing the chlorine in the pool water. So does this mean that now the pool can be kept off germs for longer periods? Unfortunately, the answer is no. What happens is that the chlorine in the water quickly binds to available cyanuric acid added to the pool water and hence only a smaller portion of the chlorine is available to serve the purpose of killing germs. So chlorine stays up longer in the pool water but not to kill the bacteria and other microorganisms which can bring in harm to you. The situation can be aggravated as cyanuric acid levels increase depriving the pool of chlorine which can keep a check on the germs. The cyanuric acid buildup can lead to far more complications.

Cyanuric Acid: Accepatble levels

The ideal level of cyanuric acid should be between 30 to 50 ppm. However, the maximum acceptable levels can be between 30 to 100 ppm.

Cyanuric Acid Buildup: Real numbers

Now let us put in some real numbers to see the cyanuric acid buildup in hot tubs.  Dichlor is mostly used in case of hot tubs for disinfection. If you have a 350-gallon tub, on using dichlor every day, about 4ppm free chlorine will be added. In this case, about 25 ppm cyanuric acid will be added to the tub in the first week. In this rate, after the first month, there will be about 100 ppm cyanuric acid.  Hence active chlorine is four times less after the first month compared to the first week.  That is 4 ppm free chlorine is equivalent to 1 ppm. Similarly after the second month, cyanuric acid will be about 200 ppm. Thus 4 ppm free chlorine becomes equivalent to 0.5 ppm. This goes on. Hope you had an idea about the cyanuric acid buildup. If the levels of cyanuric acid go up, the only way to have control over the situation is to partially drain and dilute with fresh water. This involves cost and risk. You need to consult a professional.

Cyanuric Acid Buildup in Hot tub: Negative Effects

Now we know that hot tubs are rarely exposed to direct sunlight for hours. And hence there is no need as such for cyanuric acid to be used as a stabilizer in the hot tub. Now there are people who still use cyanuric acid along with chlorine or who depend on compounds like dichlor and trichlor which have cyanuric acid in them for achieving hot tub disinfection. Cyanuric Acid buildup can deprive the pool of free chlorine needed for disinfection. It is found that the effectiveness of chlorine decreases with an increase in cyanuric acid.  There can be serious implications on the kill time of microorganisms in hot tub.  Let us take the example of pseudomonas aeruginosa, a microorganism causing hot tub rash or itch. With no cyanuric acid, the kill time is about 20 seconds. With 50ppm cyanuric acid, the kill time required is about 1 minute and 30 seconds and it can shoot up to nearly 2 minutes with 100 ppm cyanuric acid in the hot tub.

Some of the other negative effects of cyauric acid buil up are:

• Cloudy water
• Smelly water
• Itchy water leading to rashes
• Trouble in water management
• Shorter life of water with need for replacement
• Corrosion to the bath tub
• Increased maintenance costs
• Unhappy customers

What hot tub owners actually need to do?

Now as already said, there is no need for cyanuric acid to be added in hot tub water. In order to achieve the best possible way to kill germs, what you need to do is maintain proper free chlorine concentration with pH. For this, the CDC recommends the hot tub owners to have a periodic test on the free chlorine concentration and pH of the hot tub water. Chlorine concentration can be affected by many factors like pee, sweat, etc from the swimmer’s body. Free chlorine will break these components resulting in less chlorine to kill the germs. Hence routine test is essential which can throw light into the actual situation of chlorine concentration in the hot tub water. pH can also affect the reaction time of chlorine with the germs hence you need to have a check on that too. Testing can be done with the help of pool test kit and follow the manufacturer’s instruction. You do the test thrice a day or more times when the tub is used often.