Back around 1993-4 I was living in Naples. Hot water to the bath was provided by a "scaldabagno" electric immersion heater above the bath. Water in Naples is very hard and soon after we moved into the house the immersion heater stopped working. The workman who arrived to repair the fault tried to drain it, but the calcium had blocked the drain tap. He then removed the heater element (with some difficulty) which was on the base of the cylinder and then started to drill out the built up calcium using a mains powered drill. He ignored my protestations and survived - at least for that day.