Several products are available for descaling watercoolers. These are based on acids with optionally other components, such as wetting agents and colours. The choice of product depends on the preferred method employed to descale coolers. If the spring water is very high in salts based on calcium and magnesium, you will see hard water residues in the cooler reservoir. These residues are fairly easy to remove with acids.
The speed of removal depends on the concentration of the acid and the temperature of the water. Some operators prefer to use concentrated acid to obtain removal in seconds. This is OK but requires careful rinsing of the reservoir, best checked with pH indicator paper. An alternative is to use diluted acid (safer) and leave for a short soak in warm water.
The heater coils from the hot tank require a stronger acid because build-up is much worse in his part of the cooler. Never use oxidising acids such as nitric acid or chlorinated acids, such as hydrochloric, otherwise there is considerable danger of corrosion on stainless steel parts. The most cost-effective acids are based on phosphoric. Wetting agents may help with penetrating thick residues, but beware of foaming during use. Colours added to acids can act as a trace to reveal unremoved scale. However, the best all-round product is a simple acid.