Disinfecting your pool this summer

Balanced water is the term applied to pool water which is neither corrosive nor scale forming. Corrosive water may cause damage to the concrete pool shell, cement based grouts and mortars, ceramic tile finish, membranes or to the plumbing pipes and equipment, as well as cause hard deposits on the ceramic tile finish. Balanced water is a combination of calcium hardness, total alkalinity and pH value. Checking the water balance regularly and taking corrective action will avoid damage and costly repair work.
The first step in selecting grouts and sealants is to evaluate the proposed disinfection system and water source for the pool and identify factors that could result in imbalanced water.
There are several types of pool water disinfection and purification systems in use today which are; Chlorine (Sodium or calcium hypoclorite) Chlorine gas and Ozone.
Hypochlorite based systems are in-pool chemical disinfectants. They impose a high alkalinity to pool water, which typically requires adjustment of total alkalinity and then neutralisation with acid chemicals.
Neutralisation can be achieved with dry acids such as sodium bisulfate. This system is not recommended for pools with cement based grouts and mortars because sulfate levels greater than 300ppm, including high levels found in hard source water can deteriorate cement.
Latex cement grouts are more impervious to attack, although surface deterioration can still occur but at a comparatively slower rate. Epoxy grouts are immune to aggressive pool water conditions, however they will not fully protect the underlying cement based materials from deterioration.
Chlorine gas systems which have been used extensively in the past, are costly and require special equipment. However, they have great advantages in water balance which is achieved by the addition of alkaline materials to neutralise the acidifying effect of chlorine. These systems do not have problems with high total dissolved solids and acidic sulfate based chemicals.
pH Value
The term pH is used to measure the balance between acidity and alkalinity of water on a scale of 0-14, with 7 indicating a balanced or neutral state.
Swimming pool water needs to be maintained between a pH of 7,2 & 7,4.
If pH is too high (alkaline), mineral deposits will form on tiles and grout, especially at the waterline. Mineral deposits may also form beneath the surface of ceramic tiles and exert pressure resulting in decreased bond strength or delamination.
If pH is too low (acidic), etching and deterioration of cement based materials will occur. If this condition persists, grout may become rough or completely deteriorated, leading to further deterioration of adhesive mortar and levelling mortars beneath the tile.
Total alkalinity
 This measures the amount of carbonates in the pool water, which are buffering agents that control pH.
Metal content — iron and copper are common metals occurring in source water. At low pH, acidic below 7,2 metals are in solution. At normal pH, (7,2-7,8), metals are out of solution and can be deposited as a stain on ceramic tile, grout and pool fittings/fixtures.
Mineral Content — water hardness or the amount of calcium is defined as the quantity of dissolved minerals (calcium) in water. If the level of calcium is too low (below 200-250ppm), pool water will use the free calcium present in cement grout, leading to deterioration and etching. Balancing minerals (calcium) will also reduce mineral deposits on ceramic tiles, grouts, as well as prevents deposits and corrosion of pool plumbing.
Initial filling of pool — its important to monitor pool water balance during the initial filling of a pool. The pH and calcium hardness will initially rise due to the alkaline content of water soluble calcium hydroxide (free lime) of cement grouts and mortars. Free calcium hydroxide is a natural by-product of the hydration of cement.
ENJOY YOUR SUMMER!!!
– Vincent Munyeza is a Certified Pool Operator and a director of Jackson Munyeza Pools. He can be contacted on the following address: splash@jacksonmunyezapools.com