Symptoms
What it does beforeit stops.
These four behaviours each point at a different part and a different fix.
01
No hot water at all
The water is cold from the first second and at every bathroom, with the breaker up and the heater powered. Usually the element has gone open circuit inside, and the tank sits full of cold water however long you leave it.
02
The safety cut out trips
Many heaters carry a thermal cut out that kills the power when the water goes past its limit. Tripping once is a warning. Tripping again after you reset it means the thermostat is not switching off and the water is running past the set point.
03
Scalding then cold
Water that comes out hot enough to scald, or swings from hot to cold mid shower without anyone touching the mixer. The thermostat is not reading the tank correctly, either because it has failed or because its sensor is buried in scale.
04
The safety valve drips
The safety valve opens when pressure or temperature inside the cylinder climbs past its limit, which is exactly its job. Dripping all the time means something is not switching off, and capping that valve instead of finding the cause is dangerous.
Quick view
The repair, in short.
Service
Central water heater repair after a diagnosis
What we check
Element, thermostat, safety cut out, wiring and the safety valve
Where it applies
Houses, flats, chalets and blocks with a central cylinder
Coverage
All six governorates and every area inside them
Hours
Daily, 6:00 in the morning to 12:00 midnight
The order
The repair, infour steps.
The same order every time, and nobody opens a cover without proving the power is off.
We isolate and prove it dead
The heater breaker goes off and we check the terminals are dead before the cover comes off, because the element sits in water and a live terminal is not something to guess at.
We test the parts
We read the element and check whether it is leaking to earth, then watch the thermostat make and break. That names the failed part instead of swapping both and hoping.
We replace and look inside
With the element out we can see the tank floor and the state of the protection rod. A new element dropped into a tank full of sediment starts wearing from the first day, and we say so.
We fill, then power up
The cylinder is filled and vented first, and only then does the power go back on. Firing an element that is not covered by water destroys it in seconds, and that is the usual mistake after a repair.
Why it fails
Why elements andthermostats fail.
An element is a sealed metal rod with a heating wire inside it and a sheath that passes the heat into the water. Let scale build on that sheath and it becomes an insulating blanket. The heat has nowhere to go, so it collects inside the rod until the wire parts. That is behind most of the burnt elements we pull out, not heavy use.
Once the sheath cracks, current reaches the water directly, and water conducts. That is why the breaker or the earth leakage device drops every time the heater switches on, while the house behaves normally with the heater off. Pushing the switch back up and carrying on sends current into the water the house is using, and it is not something to leave.
The thermostat is a sensor held against the tank wall. It cuts the power when the water reaches its set point and lets it back when the water cools. Put a layer of scale between that sensor and the wall and it reads colder than the tank really is, so the element runs on, the water comes out scalding and the safety valve starts to weep.
That is why we test before changing anything. A new element on a failed thermostat cooks itself again, and a new thermostat on an open element does nothing at all. If the leak turns out to be the body of the tank rather than a part, we tell you repair is the wrong answer here and look at replacement instead.
External links for referenceMinistry of Electricity and Water (electricity and water supply to the building)
Repair questions
Asked about therepair.
With power reaching the heater and no hot water at all, the first candidate is an open element and the second a thermostat that is not passing current. A reading at the terminals separates them. Without it you are guessing, and guessing means changing two parts instead of one.
A thermal cut out does not trip on its own. If it goes again after a reset, the water passed its limit a second time and the thermostat is usually the reason. Leave it off until it is looked at, because nothing is controlling the temperature at that point.
The job mixes water and mains power, and the element comes out of a flange with a gasket that leaks if it goes back wrong. The tank has to be drained and the supply proved dead first. It is work better left to someone who does it daily.
Not an electrical fault. The tank is giving you less because sediment has taken up the space at the bottom. That needs a flush and a descale rather than new parts, which is servicing work. Your description on the call usually tells us which of the two it is.
It depends on the part. A thermostat and its wiring are reached from outside with the tank still full. An element sits inside, so the water level has to come down below it first. We tell you which one it is before the work starts.