Wash out’

Mains water due to fact the many of the pipes might be old collect residue along
the way. The tank has to be washed out to prevent buildup of dangerous
organisms in the tank.
Rain water still has an issue of scaling which is a chemical reaction and as water is
heated to high temperatures it leaves residue as well that needs to be washed out
at least once a year. If you believe the water source in your area is not safe, the
cleaning can be doubled per Annum. Important to note that once water is washed
out and replaced with clean cold water, it would take a day or two to have hot
water.