I was working on a project that involved changing out the customer’s inadequate hot water tank. The home was on well and septic in an area of high mineral content. An initial step was to drain the old tank for removal. The old tank was only 6 years old so I was very surprised how much mineral sludge was present. If you have high mineral content water I would advise draining your hot water tank yearly to extend its life. See photos below.

The white area is the mineral sludge.
Take a look at all of the calcium deposits. Remember that a lot of the mineral sludge ran down the drain.