Stabiliser, also known as cyanuric acid (CYA) or isocyanuric acid, protects your chlorine from being destroyed by the sun's ultraviolet (UV) rays.

Without stabiliser, the sun can destroy most of your free chlorine within just a few hours, especially during summer. This leaves your pool with little or no sanitiser, allowing algae and bacteria to grow.

Think of stabiliser as sunscreen for your chlorine. It shields the chlorine from UV light, allowing it to remain in the water for much longer and keeping your pool sanitised more efficiently.

Why is stabiliser important?

Maintaining the correct stabiliser level helps to:

• Protect chlorine from sunlight, reducing chlorine loss throughout the day.

• Reduce chlorine consumption, meaning you'll use fewer chemicals.

• Improve protection against algae and bacteria by helping maintain a more consistent chlorine level.

• Lower running costs, particularly during the warmer months.

What happens if the stabiliser is too low?

If your stabiliser level is too low, chlorine is rapidly broken down by the sun. Even if your chlorinator is working correctly, it may struggle to produce chlorine quickly enough to replace what is being lost.

What happens if the stabiliser is too high?

While stabiliser protects chlorine, too much stabiliser reduces chlorine's sanitising power. As the stabiliser level increases, more of the chlorine becomes temporarily bound to the cyanuric acid, making less of it immediately available to kill algae and bacteria.

Unlike chlorine, stabiliser does not naturally disappear very quickly. Once the level becomes too high, the only practical way to reduce it is by partially draining the pool and replacing some of the water with fresh water.