Since the water is heated to around 85-95 °C
, this actually helps in killing any microorganisms that may be present in the water. And since the water you are using comes from your local water district, it is potable and safe to use for human consumption. There is no problem with this. You are right, in doing so, you will be able to save up to 20 centavos per cup. The reason why your supplier may void your warranty if you use tap water is because of the issue of water hardness. (For detailed discussion of “hard water or water hardness”, you may Google search the topic). All tap water supplied by local water districts in almost every municipalities in the whole Philippines come from underground. For Metro Manila, the water supply comes from dams that store water from rain. Rain water is nature’s supply of distilled water. Distilled water are “soft” water, which is the opposite of “hard water”. For water coming from underground, it contains a lot of minerals (i.e. Calcium and Magnesium). As water flows and passes through embedded rocks underground, it comes into contact with them and carries with it significant amounts of calcium and magnesium salts. Water that contains a lot of calcium and magnesium salts is called “hard water”. This “hard water” causes no harm to humans, but the presence of calcium and magnesium minerals causes a whitish substance called “scale” to deposit on boiling utensils like kettle and with the case of vending machine, its boiler’s heating element. Long term boiling or heating of “hard- water” results to accumulated “scale” deposit on the heating element of the vending machine’s boiler, thus reducing its heating efficiency, eventually leading to its failure. It is this failure of the boiler caused by the use of tap water that voids the warranty. It is a choice yours to make. Save on water cost but pay for the boiler once it breaks down. You can do the math and compare which method will help you save more money with the operation of the vending machine. Please see Pictures 1 and 2 below for comparison between water kettle without and with hard water scale deposit. Picture 3 is an example of highly scaled coffee machine boiler that broke down due to using tap water (hard water) supplied by local water district.