Water testing is vital when running a pool or spa. We can perform a series of chemical tests as part of our Monthly Service Visit but it is important that certain tests are performed at least once on a daily basis. This section will help guide you through all the necessary testing procedures.

Water Sample

The main thing to consider when taking a water sample is to obtain a fair representation of the water in the pool. To achieve this, always make sure the sample is taken from the same place in the pool, ensuring this is away from the point where fresh water enters the pool. To collect the water sample rinse a plastic bottle out with pool water and submerge it 300mm below the surface.

Testing Methods

Comparator Test

The operator visually compares the colours on a comparator disc to the colour produced when a reagent is added to the water. Once the closest colour match possible has been determined the number on the disc corresponds to the level in the water.

Make sure the operator can interpret the colours correctly.

Always rinse the test tubes out with tap water before performing any tests. This removes any traces of previous tests that could affect the result.
Select the correct disc for the test and ensure all numbers are clearly visible.
When analysing the sample hold the unit up against a good light source and rotate the disc until the closest colour match possible.

Photometer Test

The operator inserts the sample into to the photometer which then analyses the sample and produces the results on a digital display.

Photometers vary depending on the manufacturer so make sure you follow the manufacturer's guidance.
Make sure the photometer unit is kept clean and dry at all times. Pay special attention to the compartments where the test tubes are placed.
Always use photometer grade tablets when using a photometer.
If a blank reagent is needed, use a clean sample of pool water.
Ensure the outside of the test tube is completely dry and free from finger marks.
The test tablet must be completely dissolved using a crushing rod.

Testing Parameters

Free Chlorine

Testing Reagent: DPD 1 Tablets
Recommended Level: 1.0 - 3.0ppm
Frequency: Twice a day (before opening and after closing). Then for manual dosing systems test every two hours and for automatic dosing systems 3 times a day.

One DPD 1 tablet is added to a 10ml sample of pool water and crushed using a crushing rod. When it is fully dissolved the sample is then placed in a comparator or photometer to gain the reading.

Please Beware: If there is a high level of free chlorine in the water (over 5ppm) it may bleach the test sample and produce a false reading. If this occurs dilute the sample 50-50 with tap water before performing the test again. Always remember to multiply the reading by 2 to get the correct level.

Total Chlorine

Testing Reagent: DPD 3 Tablets
Frequency: Twice a day (before opening and after closing). Then for manual dosing systems test every two hours and for automatic dosing systems 3 times a day.

Remove the 'free chlorine' sample from the testing instrument and add one DPD 3 tablet. Crush the tablet up using a crushing rod. When it is fully dissolved the sample is then placed in a comparator or photometer to obtain the reading.

Combined Chlorine

The combined chlorine level is calculated using the following formula;

Combined Chlorine = Total Chlorine - Free Chlorine

Testing Reagent: Phenol Red Tablets
Recommended Level: 7.2 - 7.8
Frequency: Twice a day (before opening and after closing). Then for manual dosing systems test every two hours and for automatic dosing systems 3 times a day.

One Phenol Red tablet is added to a fresh 10ml sample of pool water and crushed using a crushing rod. When it is fully dissolved the sample is then placed in a comparator or photometer to gain the reading.

Total Alkalinity

Testing Reagent: Total Alkalinity Tablets
Recommended Level: 75 - 220 ppm
Frequency: Once a week.

For this test take a 100ml sample of pool water. Add the alkalinity test tablets one-by-one until the sample turns from yellow to bright red. The alkalinity level is then calculated by the following formula;

Total Alkalinity = (Number of tablets x 20) - 10

Calcium Hardness

Testing Reagent: Calcium Hardness Tablets
Recommended Level: 75 - 150 ppm
Frequency: Once a week.

For this test take a 100ml sample of pool water. Add the calcium test tablets one-by-one until the sample turns from pink to bright purple. The calcium hardness level is then calculated by the following formula;

Calcium Hardness = (Number of tablets x 20) - 10

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