Pool & hot tub water help

Straightforward answers to the questions we hear most from pool and hot tub owners across the UK.

Whether your pH is high, your chlorine keeps disappearing or the water has turned cloudy or green, these guides explain what is going on and how to put it right safely, step by step. Not sure what the problem is? Test your water first - the analyser reads your strip and links you to the right guide.

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Getting started

How do I use pool test strips properly?How to use Deep Blue 6-in-1 test strips for your pool or hot tub: dip for 2 seconds, wait 30 seconds, then read or photograph the result.

Balancing

Why is my pool pH high?High pH makes chlorine weak and causes cloudy water and scale. What causes it and how to lower pool or hot tub pH safely, step by step.
Why is my pool pH low?Low pH makes water acidic, stings eyes and corrodes metal and heaters. What causes it and how to raise pool or hot tub pH safely.
How do I lower high alkalinity in my pool?High total alkalinity locks pH high and causes cloudy water and scale. How to lower pool or hot tub alkalinity with pH reducer and aeration.
How do I raise low alkalinity in my pool?Low alkalinity makes pH bounce around and water corrosive. How to raise pool or hot tub total alkalinity safely with alkalinity increaser.
What should my pool water hardness be?Water hardness that is too low corrodes, too high causes scale and cloudy water. The right range for UK pools and hot tubs and how to fix it.

Sanitiser

Why is my pool chlorine low?Low free chlorine lets bacteria and algae grow. Why chlorine drops in pools and hot tubs and how to raise it safely, step by step.
What should I do if my pool chlorine is too high?Chlorine too high after shocking or overdosing? How long to wait, how to bring it down safely and when it is OK to swim again.
Why does my pool smell of chlorine?A strong "chlorine" smell usually means too little free chlorine, not too much. What combined chlorine is and how to shock it away.
What is pool stabiliser (cyanuric acid) and how much do I need?Stabiliser stops sunlight destroying your chlorine. The right level for UK pools, how to add it, and what to do if it is too high.

Problems

Why is my pool water cloudy?Cloudy or milky pool water usually means low chlorine, poor filtration or water out of balance. How to find the cause and clear it.
How do I fix a green pool?Green pool water is almost always algae. A step-by-step plan to kill it, clear the water and stop it coming back.

Hot tubs

Why is my hot tub foamy?Hot tub foam comes from soaps, lotions and old water. What causes it, how to get rid of it and how to stop it coming back.
How do I use bromine in my hot tub?Bromine is a popular hot tub sanitiser. How it differs from chlorine, how to read it on a test strip and how to keep it in range.

Looking for a routine to follow? See our seasonal care plans for opening, weekly care and closing your pool, and hot tub routines.