Immersion Heater Replacement
When the tank stops heating, or only ever gets as far as lukewarm, a worn out immersion element is usually behind it. We isolate the electrics, drain the cylinder, fit a new element and seal, and get the hot water working properly again.
What's involved
An immersion heater fault is part electrical and part plumbing, and these are the pieces of it we deal with.
Element Replacement
Removing the failed heater and fitting a new element of the correct length and rating, on a fresh gasket, without straining the cylinder boss.
Cylinder Thermostat Replacement
Renewing the thermostat where it is sticking, running cold or overheating, so the new element is not switched by a worn out control.
Seized Element Removal
Freeing elements that have corroded into the boss, working steadily with the right spanner rather than forcing and splitting the cylinder.
Drain Down, Refill And Test
Draining to below the boss, refilling, bleeding the air through and checking the joint holds before the power goes anywhere near it.
Why the hot water has gone
An immersion heater is a simple thing: an electric element screwed into the side or top of your hot water cylinder, switched by a thermostat. Simple does not mean immortal. Elements scale up, corrode and eventually burn out, and in a hard water area they do it sooner.
The symptoms tend to be familiar. No hot water at all is usually a failed element or a tripped supply. Water that gets warm but never hot often points at the thermostat rather than the heater. A tank that heats at the top and stays cold lower down can mean a twin element cylinder where only one of the two is still working. Before we change anything, we test rather than assume, because fitting a new element into a fault that lives in the wiring or the thermostat solves nothing.
Most of the diagnosis is done before a spanner comes out of the bag.
The order the job has to be done in
This is electrics and plumbing in the same small space, so sequence matters more than speed.
We isolate the supply at the switched spur and the consumer unit, then prove it dead with a tester rather than trusting a switch. The cold feed is turned off next, and the cylinder drained down to below the level of the boss, which on a top entry element means draining a good deal of it.
The cover comes off and the wiring is noted before anything is disconnected. Then the old element comes out. This is the part that can be slow: an element that has sat in a cylinder for years is often seized, and it needs steady, correctly applied force with an immersion spanner. Rushing it distorts the boss or splits the cylinder, and then a straightforward job has turned into a new cylinder.
With the old one out we clean the sealing face, fit the new element on a fresh gasket, and start the thread by hand so it cannot cross. It is tightened enough to seal and no further. The wiring goes back exactly as it came off, the earth included, and the cylinder is refilled with a hot tap open so the air can get out.
More information
What we check before we leave
- The joint at the boss, watched under full pressure once the cylinder is full
- That the cylinder is genuinely full, with air bled through and no airlock left in the pipework
- Wiring connections remade tight, with the earth continuity intact
- The thermostat calling for heat and switching off at the set temperature
- The element drawing current and actually heating the water
- The cylinder jacket or insulation put back properly, not left off
- Any redundant or damaged switch or flex flagged to you
One thing worth knowing: hot water does not come back the moment the power does. A full cylinder takes a few hours to reach temperature from cold, which is normal and not a sign the new element has failed.
If the thermostat is as tired as the element, changing one and leaving the other just brings us back.
Where it fits with everything else
An immersion fault is sometimes a symptom of a cylinder that is nearing the end of its life, and we will tell you if that is what we are looking at rather than keep replacing parts on it. We work on cylinders, boilers, central heating and general plumbing, so if it turns into a bigger conversation we can have that one too.
We are based in Woodingdean and cover Brighton, Hove, Worthing, Lewes, Shoreham-by-Sea, Haywards Heath, Seaford, Burgess Hill and surrounding Sussex towns.
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The questions that come up most often when the hot water stops.
How do I know it is the immersion heater and not something else?
Can I change an immersion heater myself?
Will you need to drain the whole tank?
How soon will I have hot water again?
Should the thermostat be replaced at the same time?
My immersion heater keeps tripping the electrics. What does that mean?
How do I get a price for replacing an immersion heater?
Which areas do you cover?
Let's get your hot water back
Tell us what the cylinder is doing and we will come and put it right.
Call 01273 911551