Acids & Alkalis

pH Reducer

Sodium Bisulphate - supplied here as dry acid - is used to reduce the pH of pool water. Chlorine works most effectively as a bactericide when the pH of the water is in the range 7.2 to 7.6. Where the pH rises above 7.6 it needs to be reduced and this can be done by adding an acid such as this.

Dry Acid can be added by mixing 1.0kg of Sodium Bisulphate per 100 cubic metres of water (equivalent to 1lb. to 10,000 gallons) into a clean bucket of warm water, stirring to dissolve the granules. Then pour this liquid into the pool by the inlets, to help it to disperse thoroughly.

Allow sufficient time for thorough mixing - a few hours - then re-test and dose accordingly.

pH Increaser

This is pH Increaser - or Sodium Carbonate - also known as Soda Ash. For chlorine to work most effectively as a bactericide in water, the pH needs to be kept in the range 7.2 to 7.8, and ideally 7.4 to 7.6. ,

Where the water in a swimming pool has a low pH - near to 7.2 - it needs to be raised. This can be done by adding Soda Ash at the rate of 1.0kg to 100m3 of water (equivalent to 2.2lbs per 22,000 gallons).

Dosing arrangements: Take a clean bucket and three-quarters fill it with warm water - these granules dissolve more easily in warm water. Pour in the measured quantity and stir with a stick or spoon to help it to dissolve. Then pour off the liquid , by the inlets with the pump running to help thorough mixing in the pool. Allow 12 to 24 hours for thorough distribution and test the water again, adding more soda ash as required.

Alkalinity Increaser

It is necessary to keep the alkalinity level of swimming pool water within the range 0f 100 to 150 mg/l. or parts per million, to prevent erratic swings in the pH value as pollution and other chemicals are added to it.

Sodium Bicarbonate is added to water to raise its alkalinity level. When the alkalinity level is kept in the range of 100 to 150 mg/litre, it makes water treatment more effective and helps to prevent damage to pool equipment too.

Dose this by adding a measured quantity to a bucket that is three-quarters full of water - warm water works better - and stir to help it to dissolve. Pour off the liquid into the pool by the inlet, with the pump running, and maybe add more water to mix the solids until suspended in solution. Allow 12 to 24 hours for effective distribution (depends on flow rates and pool volume), and then test the water before dosing again.

Water Hardener

Calcium Chloride is added to swimming pool water to make it 'harder' - it increases the level of hardness salts in the water.

Calcium Chloride - when added at to a pool the rate of 1.5kg per 100 cubic metres of water, should raise the Calcium Hardness level by 10ppm. The recommended level for hardness salts in swimming pool water is 75 to 150mg/litre. If your mains water has less than 40 mg/l of calcium hardness salts it is very aggressive - hungry for calcium, and is likely to attack exposed concrete and grouting.

Dose with calcium chloride by adding a measured quantity to a bucket containing warm water. Stir well as this is slow to dissolve, then pour off the liquid into the pool by the inlet, adding more warm water to the bucket and stirring until the solids have been dissolved and added to the pool.

Calcium chloride is not expensive to add to a pool, but in soft water areas it is advisable to check hardness levels weekly and add to keep it in the range 75 to 150ppm or mg/l, as the long term cost can be high. Water that is 'calcium hungry' will attack grouting and other exposed concrete surfaces, which can cause expensive damage over the years!