Cyanuric Acid

What it is:

• You might hear it called Cyanuric Acid, Isocyanurate, or Chlorine Stabiliser – they're all the same thing.
• It teams up with your free chlorine to stop the sun's UV rays from zapping it away too quickly. Without it, your chlorine would disappear in just a few hours!
• This means you don't need to add as much chlorine, and your chlorine levels stay more even.

How much you need:

• Generally, you want to keep it between 0 and 60 PPM (that's Parts Per Million), and definitely not over 100 PPM.
• The sweet spot depends on how much sun your pool gets, what kind of equipment you have, and the water temperature.
  • Indoors: If your pool is inside and doesn't get any sun, you probably don't need it at all.
  • Warm weather (24-30°C): Aim for 45-60 PPM.
  • Cooler weather (10-20°C): Around 30 PPM should do the trick.
  • ORP sensors: If you've got one of these fancy chlorine dosers, keep the Cyanuric Acid low, ideally under 30 PPM and for sure under 50 PPM. Keep it pretty consistent too, as ups and downs can mess with the chlorine dosing.

Why it's a big deal:

• Like I said, it protects your chlorine from the sun. Without it, the sun just eats it up super fast.
• Too little? Your chlorine won't stick around long enough to keep the pool clean, you'll be adding tons of chlorine, and the levels will bounce around like crazy.
• Too much? Your chlorine won't work as well or as quickly to kill the nasties in the water. This means poor sanitisation. Plus, it can mess with those ORP readings if you have them.

How to pump up the levels:

• You add products that contain it. The most common way is by chucking in some Chlorine Stabiliser (which is just Cyanuric Acid) into the skimmer box while the pump's running.

How to actually add it:

• First, take out any socks from your filter or skimmer and give the filter a clean.
• Turn on the pump so the water's moving.
• Pour the right amount into the skimmer box. Try to mix it around a bit so it doesn't clump up into hard bits that take ages to dissolve (this is more likely in cold water).
• Keep the pump running until it's all dissolved.

How much do you need to add?

• You'll need to do a little math or just ask your local pool guru.
• You'll need:
  • Your current Cyanuric Acid level (get a test kit!)
  • The level you want it to be at
  • How many litres your pool holds
  • How many grams of the product it takes to raise 10,000 litres by 1 PPM (this should be on the packaging)
• The formula is:

(Ideal Level - Current Level) x Pool Volume / 10,000 x Grams per 10,000L per PPM = grams to add


• Example:
  • Your test says 20 PPM
  • You want 30 PPM
  • Your pool is 20,000 litres
  • The product says 20g raises 10,000L by 1 PPM
  • So it's: (30 - 20) x 20,000 / 10,000 x 20 = 400 grams

How to bring the levels down (it's a pain!):

• Lowering it is a bit of a hassle and can cost some money, so it's best to not let it get too high in the first place.
• You've got a couple of options:
  1. Special stuff that eats it up: There are bioactive products that can break down the Cyanuric Acid. They work fast but can be pricey and not always a sure thing. Chat to your pool shop about this.
  2. Diluting the water: You can drain some water and add fresh water. This will lower the concentration of everything in the pool, including the Cyanuric Acid. You can do it all at once or just let normal water loss do its thing over time (if the levels aren't dangerously high). If you go this route, don't add any stabiliser-containing products for a while.

Keeping it all straight:

• This Stabiliser stuff can be confusing because it goes by different names and is often mixed into other pool chemicals.
• The main names for the pure stuff are: Stabiliser, Chlorine Stabiliser, Isocyanurate, and Cyanuric Acid. You might also see it called UV block-out or Sunblock. Just check the ingredients label for Isocyanurate or Cyanuric Acid.
• Then there are chlorine products that already have stabiliser in them:
  • Dichlor Isocyanurate (or Sodium Dichloroisocyanurate Dihydrate): This is a type of chlorine that's usually around 56% chlorine and up to 44% stabiliser.
  • Trichlor Isocyanurate: Another chlorine type, usually about 90% chlorine and up to 10% stabiliser.
  • Anything labelled "Stabilised Chlorine" is usually either Dichlor or Trichlor. You might see it marketed as a 2-in-1 or 3-in-1 product.