The immersion heater is inside the hot water cylinder and involves heating the water using an electric heating element housed inside the hot water cylinder. The immersion heater works similarly to a kettle, relying on a metal coil that heats the water surrounding it. The immersion heater is electric, powered to electricity and can be operated through a timer to heat water at specific times of day. Some cylinders may have two immersion heaters, a top and bottom heater. The top immersion heater works when you press the Booster button to heat water quickly in a few minutes rather than needing 1 or more hours.
A good indication that the heating element in your immersion heater may not be working correctly is if you turn on the hot tap and you are not getting much hot water, or you are waiting a very long time for the hot water to heat up.
Common issues with an immersion heater can be;
Circuit breaker may have tripped
If the power supply to the immersion heater has been interrupted, this would stop the immersion heater from working. Check the circuit breaker to see if any switches have tripped, if so, push it back up and hopefully it will work. If it keeps tripping the electrics, call an electrician!
Faulty thermostat
The fix could be as easy as pressing the reset button on the thermostat. Or you may need to replace the thermostat for the immersion heater to work.
Damaged heating element
Due to age, the element may have corroded and simply need replacing.
Limescale
Limescale can cause numerous issues with a system, including damaging the heating element.
Lack of insulation
If the cylinder ‘jacket’ is no longer seated correctly around the cylinder, this could cause the cylinder to lose heat or result in the water taking longer to heat up. A quick fix of replacing the insulation might solve the issue.
A plumber or gas heating engineer can replace your immersion heater. It does make more sense to call out a gas engineer so that if the fault extends beyond the immersion heater, the engineer can repair the boiler as well while still on site.
When replacing your immersion heater, try replacing it with the same size. There should be a label at the top of the immersion heater with the specifications written on it. If you cannot see this, the heating engineer replacing the immersion heater should be able to advise you on which size heater to fit. The cost of replacing a hot water immersion heater will be dependant on a few factors;
Type of immersion heater
Copper is a more budget friendly immersion heater to fit than a titanium immersion heater material wise. Although the labour time needed to fit is the same time regardless of the material chosen.
Length of time fitting
This depends on accessibility of the hot water cylinder and the immersion heater. Hopefully the hot water cylinder is housed in an airing cupboard with space around it to access. The tank needs to be drained so the size of the tank will determine the labour time draining and refilling the tank.
Number of Heating Elements
Immersion heaters can have numerous heating elements and of course a single heating element will be cheaper but a dual heating element will save you money in the long run being more energy efficient. If you are replacing just one element on a multi element cylinder, the top element will be far quicker to replace as the water will only have to be drained just past the element. However, it may be worth getting all of the heating elements changed in one go to avoid having to go through this process again. If an element has corroded, chances are the other elements are in a similar condition and it is just a matter of time.
Descale
Removing the lime scale that is built up in the hot water cylinder will prolong the life of any immersion heater. So when changing the immersion heater, before replacing the new parts, consider also descaling the cylinder.
When gathering quotes from various heating engineers to fit the new immersion heater, budget for an engineer to be with you for anywhere from 2 hours to 4 hours of labour time.
Cost to replace an immersion heater |
Per |
Average total labour cost |
Replace a single immersion heater |
Per hour |
£270 |
Replace a dual immersion heater |
Per hour |
£290 |
Descale a hot water cylinder |
Per hour |
£300 |
Replace a top immersion heater on a dual heater |
Per hour |
£240 |
Replacing a thermostat on an immersion heater |
Per hour |
£90 |
The lifespan of an immersion heater will depend on the type of hard water area you live in and how often in a day your immersion heater comes on, heating the water. If you are in a very hard water area, prone to a lot of limescale and do not have a water softener on your system, and like to have the water set to heat numerous times of day, the immersion heater may need to be replaced every 5 years. This life can be prolonged with a descale to keep the limescale from building up around the heating element.
There are different types of immersion heaters that can be fitted to a hot water cylinder. Always be sure to take the advice of the gas engineer who will supply and fit the immersion heater and in most cases they will source like for like when replacing your immersion heater.
Some immersion heater types available for UK hot water cylinders include;
In-line Heaters
Also known as circulation heaters, and comes in a choice of material (e.g.; stainless steel, titanium, and standard steel). These In-line heaters are easy to install and efficient.
Flange Heaters
Flange immersion heaters are compatible with oil, fuel, water, gas, and thermal fluids, coming in shapes including straight or L-shaped. They offer the best resistance against corrosion.
Screw Plug Heaters
Screw plug immersion heaters are low-maintenance options that can heat different fluids, liquids and gases with direct contact.
Over the Side Heaters
These immersion heaters are easy to maintain and take up only a small amount of space as they are installed on the top of a tank. The element directly engages either on the side or bottom of the tank.