How an immersion heater works
An immersion heater is an electric element screwed into the top or side of your hot water cylinder, with a thermostat controlling how hot the water gets. Many homes use it as a backup to the boiler; in properties without gas, it may be the only source of hot water.
Because it heats water directly with electricity, an immersion is simple and reliable — but the element and thermostat are both wearing parts, and in hard-water areas like ours they work harder still.
Common faults
The usual symptoms are no hot water at all, water that is lukewarm, or a fuse or breaker that trips when the immersion is switched on. A failed element is the most common cause, followed by a faulty thermostat that either cuts out too early or stops cutting out at all.
Limescale is the enemy here. Scale coats the element like a blanket, making it work harder to heat the same water until it eventually burns out. If your element has failed and the water in your area is hard, fitting a scale reducer or choosing a scale-resistant element is worth discussing.
Repair or replace?
Replacing just the element or thermostat is often all that is needed, and we will always check that first rather than assuming the worst. The wider question is the condition of the cylinder itself: if it is old, scaled up or showing signs of corrosion, a new element may only be a short-term answer.
We will give you an honest view. If the cylinder has plenty of life left, a new element is money well spent; if the cylinder is on its way out, we would rather tell you than fit parts into something that fails next year.
What affects the cost
The cost of an immersion heater repair or replacement depends on a handful of things: whether it is the element, the thermostat or both; the type and size of element your cylinder takes; how accessible the cylinder is; and whether the wiring and switch need attention too. Draining and refilling the cylinder adds time on some systems.
We check the fault first, explain what has failed and agree the price with you before any work starts — so the figure never comes as a surprise. For wider hot water problems, our heating and boilers page covers the rest of the system.
Areas we cover
We repair and replace immersion heaters across Harpenden, St Albans, Wheathampstead, Redbourn, Luton and Hemel Hempstead. Our areas we cover page lists the rest.