Water, clarity and algae
Stabiliser and cyanuric acid in pools
In strong sun, unprotected chlorine disappears quickly. Stabiliser slows that down — until there is so much of it that chlorine stops working well.
Cyanuric acid, sold as pool stabiliser or conditioner, binds loosely to chlorine and shields it from ultraviolet light. In an outdoor Dubai pool without it, chlorine can be lost from the water within a single sunny day. With a moderate level, chlorine lasts much longer.
Water guides explain what a reading or a symptom means and the order in which to correct it.
The problem is that stabiliser does not leave the water except by dilution. Stabilised chlorine tablets and granules add more with every dose, so levels creep up over months. At high levels, chlorine becomes slow to act, algae and cloudiness appear despite normal chlorine readings, and the usual fix is to replace part of the water.
The short version
It protects chlorine from sunlight
A moderate level keeps chlorine in an outdoor pool much longer.
It only leaves by dilution
Backwashing, splash-out and part-draining are the only ways it goes down.
Too much weakens chlorine
High stabiliser makes chlorine slow, so algae can grow at normal readings.
Managing stabiliser
Testing it
Stabiliser has its own test; it is not shown on a basic chlorine and pH reading.
Choosing the chlorine type
Liquid chlorine and salt chlorination add no stabiliser, so they help keep levels steady.
Lowering a high level
Partial draining and refilling reduces it; the amount depends on the reading.
Check stabiliser if you see these
Algae despite chlorine readings
Over-stabilised water can grow algae at levels that look adequate.
Long-term tablet use
Months of stabilised tablets almost always raise the level.
Chlorine vanishing on sunny days
Very low stabiliser lets sunlight burn chlorine off.
Common questions
Do indoor pools need stabiliser?
Usually not, because there is little UV to protect against.
Do salt pools need stabiliser?
Outdoor salt pools usually benefit from a moderate level to protect the chlorine the cell produces.
Can stabiliser be removed with chemicals?
Products exist, but dilution is the dependable way to reduce it.
Related pool care guides
- Why a pool smells of chlorineAnother water problem with a related cause.
- Pool water that stings eyes and skinAnother water problem with a related cause.
- Stabilised or unstabilised chlorineA related choice about how the pool is looked after.
- Chlorine shock or non-chlorine shockA related choice about how the pool is looked after.
This guide sits under pool water treatment. Browse all pool care guides. We look after pools at homes and commercial properties across Dubai.
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Next step
Not sure about your stabiliser level?
Tell us how you chlorinate and send a recent test. We will check stabiliser and suggest a plan.