Carefully balanced water is the key to succesful and trouble free pool ownership. Once the water goes out of balance it gives bacteria, algae and viruses ideal conditions to grow. This in turn can lead to infections and sickness in bathers.

Conversly, if the water is out of balance because chemical levels are too high, it will cause bather discomfort, rot clothing and pool equipment.

Pool water testing is carried out with reagents that change colour according to the level of chemicals in the water. The reagents are either tablets or liquid. A normal domestic kit tests for pH and total chlorine levels. Professional test kits work in the same way, but test in more detail.

pH is the relative level of acidity or alkalinity. If the water is too alkali, limescale deposits may build up. Too acid and the grout will be eaten out from between the tiles. The pH needs to be around 7.2, which is safe for our skin. If the readings are out, itchy dry skin can result. The chlorine is also most effective at this level.

The chlorine level needs to be high enough that the water will be sanitized, but not so high that it damages peoples clothing and skin. Chlorine is a very dangerous chemical and in high doses can be a serious health risk.

AT A GLANCE

CHLORINE 1.2 TO 2.5ppm

pH 7.2

If you have water quality problems, test before taking action.

Adding chemicals at random, is dangerous and wasteful.

How to test

manufacturers kit requires different amounts of reagent, some require 3 drops, some 5 and others use tablets.

Turn the vial upside down and then dip in the water, take the sample from 20cm below the water surface. This is because UV light will breakdown the chlorine in the water towards the surface.

Add the drops/ tablets then compare the colour of the sample to the scale.

What action do I take once I have my readings?

LOW pH

Add pH plus to raise the level. Do not do this rapidly, little by little is best, around 1kg per day till the level reads correct.

If pH is too low, this means the pool water is acidic and will corrode stainless steel, eat away the grout and be generally unpleasant to swim in.

HIGH pH

Add acid or pH minus. If using acid be very careful as this is very corrosive and will burn skin and clothes. For domestic applications, a powdered dry acid is best.

High pH may result in scale build up.

LOW CHLORINE

As chlorine disinfects the water, a low level leaves the water vulnerable and it will quickly go cloudy then green.

Add stabalised chlorine if there is a reading but just low. If there is no reading of chlorine and the pool is in use, then it needs to be shocked, by adding unstabalised chlorine. This will sanitise the water, but not leave a high residue that would be uncomfortable for swimmers.