Water, clarity and algae
Partially draining and refilling a pool
Some water problems cannot be fixed with chemicals. Replacing part of the water is sometimes the simplest and cheapest answer.
Stabiliser, calcium hardness and total dissolved solids build up gradually from dosing, evaporation and top-ups. Once they are high, chemical fixes become slow, expensive or impossible — stabiliser and calcium in particular are reduced practically only by dilution. Replacing a calculated share of the water brings them back into range.
Water guides explain what a reading or a symptom means and the order in which to correct it.
Draining is done carefully. Taking a pool completely empty can risk damage to the shell or finishes, particularly where groundwater is high, and exposes surfaces to strong sun. Partial draining, with the level kept above key fittings and refilled promptly, avoids most of those risks.
The short version
Dilution is the fix for build-up
High stabiliser, hardness and dissolved solids come down only by replacing water.
Partial is usually enough
A calculated share of the water corrects the reading without emptying the pool.
Rebalance after refilling
Fresh water brings its own alkalinity and hardness.
How it is done safely
Working out how much
The current and target readings decide what share of the water to replace.
Draining under control
Using the filter waste setting or a submersible pump to an appropriate discharge point, with equipment switched off when the level falls.
Refilling and balancing
The pool is refilled promptly, then tested and rebalanced before normal use.
Before draining any water
Confirm dilution is the answer
Retest; some problems that look like build-up are caused by something else.
Check where water may go
Community and building rules may set where pool water can be discharged.
Protect the pump
Turn equipment off before the level drops below the skimmer.
Common questions
Can I drain the whole pool?
Fully draining carries risks to the shell and finishes. Take advice for your pool before doing it.
How often is part-draining needed?
It depends on the chlorine type and how much water is topped up. Pools using stabilised tablets need it more often.
Does part-draining waste water?
It uses water, which is why it is done only when testing shows it is needed.
Related pool care guides
- Removing scale from pool tilesAnother water problem with a related cause.
- When pool pH is too highAnother water problem with a related cause.
- Liquid chlorine or chlorine tabletsA related choice about how the pool is looked after.
- Test strips or a liquid test kitA 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
Considering draining the pool?
Send your latest test results. We will tell you whether part-draining is needed and how much.