Hot Tubs, Swim Spas, Service, and Maintenance

Stabilizer, CYA, Conditioner...


What happens when I have too much?

It seems that whenever we are explaining pool water chemistry and get to the point about CYA (A.K.A. cyanuric acid, stabilizer, water conditioner), the customer's eyes lose focus and we know that we have lost them.  Too much information has been given and the pool owner will forget what we have told them. Many customers get confused and think that we are talking about muriatic acid. Muriatic acid is the acid that lowers ph and alkalinity. Cyanuric acid and muriatic acid are completely different acids. They are not one and the same and are designed to do two completely different functions.

"The important thing to remember is chlorine and keeping my pH in balance, right?" they inquire hopefully, thinking that their pleadings will make their pool water not need so much attention.

"You need stabilizer too." We remind them, and then go on to explain how an outdoor pool (especially in the St. George desert heat) needs the proper amount of CYA to help keep the chlorine from evaporating.  If they don't put enough in they will keep having to put in a ton of chlorine because it won't stay 'stabilized' in the pool.

But, where does the chlorine go?  What is happening to it? If 20 parts per million of CYA is good, why don't I want to put in more so that my chlorine will last even longer?  Well, if you have ever had any curiosity about CYA, stabilizer or conditioner, here is the rundown on why having the 'right' amount is really important for your pool, and why too much of it is a bad thing.

What is it?

Cyanuric acid is a weak acid that is marketed as a chlorine“stabilizer” for swimming pools.  Other terms used by the pool supply industry are “isocyanurates”, “conditioner” or “CYA”.  When exposed to the ultraviolet rays of the sun, the free chlorine in the pool water will break down and escape.  Cyanuric acid is intended to reduce this loss of chlorine." (Pennsylvania Department of Health)

In our store, the brand we sell calls the cyanuric acid "Primo Powder."  Having a few names is confusing for customers, and this is probably one of the reasons people either don't know that they need it, or are confused about it.  Another reason pool owners seem to be confused about cyanuric acid is that it is a product that you don't have to put in very often because it doesn't leave the pool water unless you drain it or have splashed out and put in fresh water.  Because of this, people tend to forget about it.

How do I get it in the pool?

At Tropical Bullfrog Spas we recommend that you check your cyanuric acid levels regularly for a few reasons.  Chlorine, in the form of dichlor (shock) and trichlor (tablets), is also known as isocyanurates.  They both contain cyanuric acid, so every time you add shock with dichlor or tablets with trichlor, you are adding cyanuric acid (CYA) to your pool.  But, since this level is usually not quite enough to start a pool out, "Water Conditioner" is cyanuric acid sold in a granular form that a pool owner adds to a pool, usually only at the beginning of the swimming season, or when they have added a lot of fresh water. A three-inch tablet of trichlor has about 2 ppm of CYA and a 1 lb. bag of shock (dichlor) has about 1.5 ppm of CYA. 

HELP!! My pool store is telling me to drain my pool!
Can you get too much?

Unfortunately, you can get too much CYA in your swimming pool, and this is something we try to warn customers about from the beginning (which is usually when they are too new to having a pool and they have just been bombarded with too much chemistry information). How does this happen and what can you do about it?  Well, it happens in a few different ways...

  1. Putting too much "Water Conditioner" in in the beginning.  This usually happens because someone puts it in without testing to see how much is in the pool before they put more in.  *Remember*, it doesn’t leave the water, and generally the only time you need to put it in is with a new pool or after a fresh fill. Pool owners with sand filters who can vacuum to waste or who backwash are putting in more freshwater than pool owners with cartridge filters, so they may need to put in more CYA than others.  Always, always, always, get your pool water analyzed at our store before you add more "Water Conditioner/Cyanuric acid" to see what level you are starting with.  Then, if the computer says to add 5 lbs., start with 3.5 and recheck, just to make sure you don't overdo it.  It is much easier to slowly add it than to have to drain your pool. This leads to the second way it gets in your water and the reason you don't want to start out with a high number in the beginning of the season...
  2. Chlorine Tablets made of trichlor have CYA in them and add about 2 ppm (parts per million for those of you who don't speak 'pool water chemistry' yet) and every time you dissolve one to add chlorine you are adding more CYA.  Now, in some climates, maybe you don't go through so much chlorine, but we sure do here, in sunny Southern Utah, when we have weeks of 100+ temperatures and the pool is filled with kids for hours a day.  That is a lot of chlorine to go through, and the levels of CYA go up pretty quickly.  Then, if you add granular shock (and you better add shock if you want your pool to look clean) you will add more CYA because shock is made from dichlor and it has about 1.5 ppm of CYA per pound. Our suggestion is to shock your pool with liquid chlorine so the CYA level doesn't climb as quickly. 

I have too much, big deal?  I still don't see why I have to drain my pool!

The ironic thing about CYA... you need it so the UV rays from the blazing sun don't eat your chlorine up and leave you with an unsanitized dirty, bacteria-infested pool.  But, if you let the levels get too high, the CYA will reduce the overall effectiveness of the chlorine, making your pool unsanitized, dirty, and bacteria-infested...basically the thing you were trying to avoid when you added the CYA in the first place.

So what is the right level?  How do you get the perfect amount without getting too high?

  1. Buy slow dissolving chlorine tablets.  BE WARY OF CHEAP CHLORINE AT BIG BOX OR DISCOUNT STORES.  These tables look like they are a great price compared to what you can get them for at your local professional pool store, but there is a big difference.  The tablets that you get at a big box or discount store (not naming names 🙂 dissolve too fast and therefore are putting too much CYA into your pool too fast.  I see it every summer, customers coming in to get their water tested and can't believe that their CYA levels are so high, and the thing they usually have in common is that they bought cheap chlorine, thinking it would save them money.  In the end, they have to spend more money to drain and refill their pool (not to mention the alkalinity and pH problems it is causing...but that is a whole other article).
  2. If you know your levels are getting high, start to use liquid chlorine because it has no CYA in it.
  3. Drain part of your water on a more regular basis, if you can.  Even a partial drain can help, because the freshwater will dilute the CYA.  Test your levels and when it starts to get on the high side, above 80 ppm, do a 1/3 or 1/2 drain. It is usually easier to dump a little water than the entire amount.  If CYA is above 150 ppm on a pool that is sanitized by chlorine tablets and shock, a complete drain is needed to lower CYA below 30 ppm.  There will most likely be enough residual CYA in the pipes.

How much is too much?

Here are some general guidelines about CYA and the amount that you should have in your pool.

MAXIMUM LEVEL IS 150 PPM, at least according to many states. Health departments generally will not let county pools have more than 30 ppm.  Chlorine really loses its ability to sanitize when CYA reaches 100 PPM or higher because all the CYA is bonding with the chlorine, and the time it takes to kill bacteria lengthens as the concentration of CYA increases. When CYA is too high you will need to have a lot more chlorine in the pool to work, (and then you are probably putting in more CYA at the same time...a vicious cycle)

20-30 ppm is ideal for an outdoor pool that uses three-inch chlorine tablets.

60-80 ppm for a salt system.  The reason you have more CYA with a salt pool is that you are not ever adding any extra CYA to your pool and need to start out with enough to keep the chlorine from evaporating. But, as I said before, check your levels of CYA before adding it.  (If you are not in a real hot climate, you can keep your levels lower too).

If you have over 150 ppm our professional testing equipment will not let the customer have their water analyzed and tell them they need to lower the CYA by draining.  Some customers don't want to drain and keep coming back wanting their water tested, but it gets tricky at that point.  We like to start warning customers when they get close to 100 ppm so that it doesn't come as a complete shock when you need to drain. Draining is best to do in the spring or fall rather than in the middle of the swim season.


Alkalinity keeps your pH in balance.  When it is too high, pH tends to get locked, and when it is too low, pH tends to bounce all around (again, this is a good topic for another article and too much to talk about here). CYA affects the pool's alkalinity levels quite a bit the higher it gets and unless the pool owner realizes what is going on, they can really get their alkalinity messed up.

In short, when CYA gets high, like say a nice number of 120, you take 1/3 of that number and you remember it (40).  Now let’s say you do an alkalinity test with your test drops and you get 12 drops for your blue reagent to turn yellow or red to turn green and you do your math calculations and figure out that your alkalinity is 120.  Well, under normal circumstances this sounds like a great number for your alkalinity, but, your pH keeps bouncing all over the place and is really low.  So, you wonder what is up since alkalinity seems to be fine.

Well, your alkalinity is not fine when your CYA is that high.  You must take 1/3 of your CYA and (do more math) subtract that from the alkalinity to get your adjusted alkalinity.  120-40 = 80, and for our recommendations, that is too low for your alkalinity and could explain your pH problems. Remember low pH is corrosive!


You need CYA in your pool, but just not too much.  If you do get too much, you really are better off draining because you usually have to spend more money adjusting your alkalinity, and once the number is over 150 there is no real way to know how high it is so we are just guessing.