How to make sure you always have hot water on tap

All you need to know about that kilowatt-hungry kettle in the hot press — the immersion tank

Water heated in a traditional immersion linked to a wet central heating system run on kerosene, for instance, is old technology, but it remains very clever. File pictures

Now that autumn's on the horizon, we need to talk about the immersion tank. With the latest advances in central heating and domestic hot water technology, the grand old, unsupported Irish immersion tank is something of an antique. Electricity is an infamously expensive way to heat water. Still, an estimated 700,000 of us are not able to claw our way over to the natural gas network, are still using oil, and are consequently still stuck with that great steel or copper kettle in the hot press. There are things we can do to optimise our immersion tank’s thermal efficiency. Let’s put some manners on the old dear.

Before we start, how is the water heated in a traditional immersion linked to a wet central heating system run on kerosene, for instance? This is old technology, but it remains very clever. Most have two sources of energy — the CH boiler and electricity. In what is termed, indirect-hot-water heating, when the CH boiler is either set to heat domestic water, or the entire central heating is up and running, a copper coil acting as a heat exchanger, indirectly warms water in the immersion tank. The tank can be vented or unvented depending on your system set-up.