1. Work out how much water you need

Before you start, you need to know how many litres or cubic metres (m³) your pool holds. For a rectangular pool: length × width × average depth, in metres. Each m³ is 1,000 litres. If your pool has a different shape, use our calculators by pool shape.

For pH-, it is worth buying large containers, as it is the product you use most. For salt, always choose a good brand and a clean one.

Make a note of the volume in m³: you will need it to work out the product doses in the following steps.

2. Choose how to fill it

You have two options: fill it with a hosepipe, if your municipality allows it, or hire a water tanker.

With a hosepipe: it can take several days and your water bill shoots up.
With a water tanker: each tanker delivers 12,000 litres and the pool is filled in a single day. A 48 m³ pool takes 4 tankers.

3. Test the water

Once the pool is full, test the water levels to see what needs correcting. 6-in-1 test strips are easy to use and inexpensive: they measure total chlorine, free chlorine, pH, alkalinity, hardness and cyanuric acid.

4. Adjust the hardness

Hardness measures the amount of minerals dissolved in the water, mainly calcium and magnesium salts. The ideal value is between 200 and 400 mg/l (20 to 40 French degrees).

If it is low: add a hardness increaser, 1 gram per m³ for every mg/l you want to raise it by, spread over several doses and following the manufacturer’s instructions.
If it is high: add a hardness reducer, 1.5 grams per m³ for every mg/l you want to lower it by. Let the water circulate for about 3 hours, add liquid flocculant (10 ml per m³), leave it to settle for 3 days and finish by cleaning the bottom with the pool cleaner.

5. Adjust the alkalinity

Total alkalinity is closely linked to pH: if you do not keep it under control, you will struggle to keep the pH stable. The recommended value is between 125 and 150 ppm.

If it is below 125 ppm: add an alkalinity increaser, 1.8 grams per m³ for every ppm you want to raise it by.
If it is above 150 ppm: ask your pool shop, because lowering it requires a more delicate treatment.

6. Adjust the pH

pH measures whether the water is acidic or alkaline. In a pool, the ideal is to keep it between 7.2 and 7.6.

Pool water pH scale showing the ideal range between 7.2 and 7.6

To raise it: pH increaser, 20 grams per m³ for every 0.1 you want to raise it by.
To lower it: pH reducer, 20 ml per m³ for every 0.1 you want to lower it by.

7. Chlorine or salt

Chlorine: the level should be between 0.6 and 1.5 mg/l. To start with, add 15 grams per m³ of shock chlorine.
Salt chlorination: add the salt directly to the pool. Check the amount your electrolysis unit requires; the usual range is 4 to 7 kg per m³.

8. Start the filtration

Open the valves for the skimmer, the main drain and the return to the pool, and leave the pool cleaner and drain valves closed. Set the filter valve to the filtration position and switch the pump on in manual mode from the electrical panel. If all is well, the water will pass through the pump and come out of the return jets.

To find out how many hours a day the system should filter, divide the water temperature by 2. For example, with the water at 24 °C: 24 ÷ 2 = 12 hours.