If your immersion heater has stopped producing hot water, the fault is almost always one of four things: the thermostat has tripped or failed, the heating element has burned out, the timer or switched spur is not supplying power, or the circuit has tripped at the consumer unit. Start by checking the switch and the fuse board, then press the reset button on the thermostat if the model has one. A replacement element or thermostat in Glasgow costs £120 to £280 fitted, and the job usually takes an hour.
Immersion heaters are the most ignored appliance in the house right up to the morning there is no hot water. Here is how to work out what has failed and what it costs to put right.
How an Immersion Heater Works
An immersion heater is an electric element that sits inside your hot water cylinder, much like a giant kettle element. It is controlled by its own thermostat and usually switched from a fused spur or a timer. Many homes use it as backup to the boiler; some flats and older properties rely on it entirely. Cylinders often have two elements — a short one at the top for a quick boost, a longer one lower down for a full tank.
Common Causes of No Hot Water
Tripped thermostat
Most immersion thermostats include a thermal cut-out that trips if the water overheats. It is the single most common cause. There is a small reset button under the thermostat cover, and pressing it often restores hot water immediately. If it trips again within days, the thermostat itself is failing and should be replaced rather than reset repeatedly.
Burnt-out element
Elements fail with age, and hard water scale accelerates it. Symptoms are no heat at all despite power reaching the unit, or water that heats far more slowly than it used to. A scaled element also uses noticeably more electricity before it dies.
Power supply fault
A tripped RCD, a blown fuse in the spur, or a failed timer will leave a perfectly healthy element doing nothing. Always check the consumer unit before assuming the worst.
Timer or programmer failure
Older mechanical timers stick. If the immersion heats when you override the timer but not on schedule, the timer is the fault.
Wiring and connections
Heat cycling loosens terminals over years. Scorching at the connection block is a genuine fire risk and needs attention immediately, not next month.
Safe Checks You Can Do Yourself
- Check the switch on the wall is on and the neon is lit.
- Check the consumer unit for a tripped breaker or RCD, and reset once.
- Override the timer to constant and wait an hour — if the tank heats, the timer is the problem.
- Feel the cylinder. Warm at the top only usually means the top element is working and the lower one is not.
- Look for the thermostat reset button under the cover cap — but only with the power isolated at the spur.
What to leave alone
Do not remove the element yourself. It is under water pressure, needs the cylinder draining first, and requires a large box spanner and a new gasket. Do not rewire the spur or the thermostat unless you are qualified — this is a high-current circuit. And do not keep resetting a cut-out that keeps tripping, because it is protecting you from a genuine overheat.
Immersion Heater Repair Costs in Glasgow (2026)
| Job | Typical Glasgow price (2026) |
|---|---|
| Diagnostic call-out | £70 – £110 |
| Thermostat replacement | £120 – £190 |
| Element replacement (standard cylinder) | £180 – £280 |
| Both element and thermostat | £220 – £340 |
| New timer or switched spur | £90 – £180 |
| Full cylinder replacement (vented) | £650 – £1,100 |
| Out-of-hours attendance | £110 – £180 on top |
If the cylinder itself is more than twenty years old, or heavily scaled and corroded, replacing it can be better value than fitting a new element into a failing tank. We will tell you which case you are in before spending your money.
Glasgow-Specific Considerations
Glasgow’s water is comparatively soft, which is good news for element life — scale failure is far less common here than in southern England. What we do see is age. A great many cylinders in tenement flats and older Paisley and Southside properties are original to a 1980s or 1990s refit, with foam-lagged vented tanks and elements that have never been touched. Access is the other issue: cylinders sit in cramped airing cupboards with the element facing a wall, so allow time for the engineer to make space.
Newer properties in East Kilbride and other estates usually have unvented cylinders, where the immersion is a backup to the boiler. Those are pressurised systems and legally require a qualified engineer for any work on the cylinder itself, including the immersion boss.
Should You Repair or Replace?
- Repair if the cylinder is sound, under fifteen years old, and it is a single element or thermostat failure.
- Replace if the tank is corroded, weeping at the boss, badly scaled, or if you are already planning a heating upgrade.
- Rethink the system if you rely on the immersion daily because the boiler no longer heats water — that usually points at a boiler repair or a diverter valve rather than the immersion at all.
Electric-only hot water is expensive to run, so if the immersion is doing work the boiler should be doing, fixing the central heating side usually pays back quickly. The Energy Saving Trust publishes current comparisons of electric versus gas water heating costs.
Why Choose a Gas Safe Certified Engineer?
An immersion fault is often tangled up with the boiler, the cylinder controls and the motorised valves, and diagnosing it properly means understanding the whole system rather than just the element. A registered Gas Safe engineer can test the lot in one visit, and can legally work on the boiler side too. Check any card on the Gas Safe Register. Our emergency heating repair cover runs seven days a week for no-hot-water calls.
You may also like our guides on water pressure problems and what to do when you have no heating.
Frequently Asked Questions
Why has my immersion heater stopped working?
Most often a tripped or failed thermostat, a burnt-out element, or no power reaching the unit because of a tripped breaker or failed timer. Checking the switch and consumer unit first rules out the cheapest causes.
How long does an immersion element last?
Typically ten to fifteen years in Glasgow’s soft water, less if the cylinder has heavy sediment or the element has been run constantly.
Can I replace an immersion heater myself?
We would not advise it. The cylinder must be drained, the element needs a specific box spanner and a new gasket, and the circuit is high current. Corroded elements often shear, turning the job into a cylinder replacement.
How much does it cost to replace an immersion heater?
£180 to £280 fitted for a standard element, or £220 to £340 if the thermostat is replaced at the same time. A diagnostic-only visit is £70 to £110.
Is it expensive to run an immersion heater?
Compared with gas water heating, yes. Running one as backup for a day is fine; relying on one permanently because the boiler is faulty usually costs more per month than the repair would.
My water is warm but not hot — what does that mean?
Commonly a failing thermostat set too low, or a top element working while a lower element has failed, so only the upper part of the tank heats.
Ready to Get Started?
Precision Renovators are Gas Safe certified plumbing and heating engineers covering Glasgow, Paisley, East Kilbride and the surrounding towns. We diagnose before we quote, put the price in writing, and tell you honestly when a cylinder is past repairing. Browse our services or see our projects.
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