By Terry Arko
Why is it important to routinely test pool water? The answer is simple: the state of water in a pool can be unpredictable and chaotic when it is not properly managed. The water itself is an unruly element. This liquid comes with a whole list of demands from the very day the tap is turned on. When water is added to a constructed hole in the ground, it will enter with either the need to consume or unpack. Immediate action is required to control the potential chaos coming from the very existence of water.
Calcium (Ca) is the primary ingredient water has a hankering for. When water is hungry due to lack of sufficient calcium, it goes on the hunt to find it. In a plaster or aggregate pool, it will seek its food in the material of the surface. Plaster and other cementitious surfaces have plenty of calcium. To keep the integrity of the surface, a minimum amount of a calcium additive, such as calcium chloride (CaCl2), must be added. The minimum calcium to start must be 150 parts per million (ppm). To ensure this, a calcium hardness test is required.
Before adding any water to a newly surfaced pool, the source should be tested for calcium. One should never wait until the pool is filled before testing for calcium levels as it could lead to aggressive fill water taking calcium from the surface while the pool is being filled. There are startup systems which allow owners to add calcium as their pool fills to prevent any of it from being taken from the surface.
The ideal level of calcium for plaster pools is 350 ppm. For vinyl liner and fibreglass, it is 250 ppm. If the pool is in a hard water area, the source should be tested first as well. Hard water contains high amounts of calcium. This will unpack what it cannot hold in the form of a calcium carbonate (CaCO₃) scale, this makes it even more important to perform a calcium hardness test of source water before filling a pool.
