Should You Or Should You Not Use CYA In Your Swimming Pool?

In Blog, Chemistry by Aaron Donohue

Every year when summer comes around I start getting the questions about whether CYA or “Stabilizer” is necessary.  For most of my clients I will say no, but there are a few cases where I might say yes.

First, CYA (cyanuric acid) should only be used in outdoor pools where required, it should never be used indoors; it is actually illegal to use indoors in various states, and is outright banned altogether in others.

The purpose of CYA is to prevent chlorine from being broken down by UV rays. This is accomplished by the CYA and the chlorine forming a temporary bond which protects the chlorine from the UV. This results in chlorine residuals that do not drop off as quickly as they otherwise would, thus “stabilizing” the chlorine levels in the water over a given period of time.

It is important to note however, that while the chlorine is still there while bound to the CYA it is less effective at sanitizing the water. This requires a slightly higher total chlorine residual to achieve the same sanitation potential.

Also, CYA is not readily removable, so once added is effectively “permanent” until the water is diluted.

Here’s the thing, if you are talking about a low use pool where the testing is only done once or twice a day at most,(e.g: residential pool, HOA, Camp Grounds, etc.) you’ll probably get a better result by using CYA, just bump the residual up, add the CYA and go on about your day. You don’t want to risk having zero chlorine and not knowing about it.

If, however, you are running a high demand facility (rec. pool, water park, municipal pool, summer camp. Etc.), you do not want your chlorine to be bound up and ineffective; you want it to sanitize the water, and to do it quickly!

In this case, I would consider scrapping the CYA, and just bite the bullet on more chlorine use. You will need to add more chlorine during the daytime, but your chlorine will be more effective.

*(For those with fixed max outputs (e.g. Chlorine generation) this means that supplemental chlorine may be required.)

CYA may also impact chemistry controller operation which is a big factor for commercial facilities who depend on them.

CYA levels should not exceed 25 ppm.

Some sensors can be thrown off a little and will just need a slight adjustment while others will be rendered completely useless in the presence of CYA.

It is important to understand how compatible your controller is with CYA before adding.  Most manufacturers will have a section on CYA that explains how the controller will react to it, be sure to check this out and if you do not find it, call them!

What will you do this summer?