It usually happens when you have just 15 minutes left before you have to run out the door to work. What a shocking way to start the day.

Hot water is a household essential most people take for granted until it isn’t there.

Both electric and gas systems require a specialist technician to maintain and repair.

“Electric hot water systems draw a potentially lethal amount of current and only a specialist should work on them,” says Sharpe Group spokesman David Sharpe. “The same goes for gas hot water systems but having said that there are basic steps householders can take to ensure peak efficiency.”

First keep a simple maintenance log of regular visual inspections, for leaks and whether the storage water cylinder’s overflow is excessive.

“It is quite normal for a small amount of water and condensation to drip during the heating cycle but anything more should be investigated by an expert,” says Mr Sharpe.

The problem could be as simple as a worn-out pressure relief valve, which is easily replaced, or an indication of an impending major failure within the tank unit.

Compare your power bills season by season. A spike in water heating costs could indicate a leak within your household plumbing network. This could be as simple as a leaking washer in a hot water tap that isn’t used much.

“It is surprising how much water can be lost this way,” says Mr Sharpe.

 Every year a licensed specialist should service the whole system. This may take up to an hour and involve draining the water heater to flush any sediment build-up.

 Most storage based electric systems contain a sacrificial anode attracting minerals and impurities that would otherwise corrode the tank’s internals. The anode slowly deteriorates, being sacrificed to protect the system. It should be replaced at least every five years.

 “This is one of the most important maintenance tasks,” says Mr Sharpe, “and can add many years to the life of a hot water system.”

  So the main message is: Don’t wait for your hot water system to break down before you start thinking about it.