Makes we repair
What no hot water usually means
No hot water most often comes down to a boiler fault, Vaillant and Glow-worm both say. A boiler with a fault shows a code on its display. The makers' own checklists start with simpler causes, though:
- the power
- the settings
- the pressure
- the water supply
- the condensate pipe, in a frost
Some of these you can check yourself, safely, and the rest are an engineer's.
The kind of boiler changes what to check. A combi heats water as you run the tap, with no tank or cylinder, so when it stops, the taps run cold. A system or regular boiler heats a cylinder that stores the hot water. With a cylinder, the fault can be in the cylinder's controls as well as the boiler. Every boiler problem, and what each usually means.
Sources: Vaillant's and Glow-worm's pages on no hot water, Viessmann's and Alpha's checklists, Vaillant's page on the diverter valve, and Ideal's boiler FAQs.
The other causes, by what else is happening
The other causes of no hot water show in what else the boiler is doing. Three things point the way:
- whether the heating still works
- whether the boiler is a combi
- whether the water runs hot and cold
The makers' own pages name each cause.
Sources: Vaillant's pages on no hot water and the diverter valve, Glow-worm's page on no hot water, Ideal's boiler FAQs, Viessmann's advice on no hot water, Alpha's FAQ, and the user guides and manuals of Worcester Bosch, Alpha, Main, Biasi and Vaillant.
Worth knowing
On a combi, hot water that comes when the heating is on, and not when it's off, is a sign of a stuck diverter valve. Vaillant says the fault often shows first in the warmer months, when the heating isn't needed.
What you can safely check
The safe checks for no hot water are the ones the makers' own guides give a householder. Never take the boiler's casing off, and never touch anything that carries gas.
1. Is the boiler on, and is there a code?
A blank display can mean the power is off. Check the boiler's switch, and the fuse box for a tripped fuse. After a power cut the boiler restarts by itself, but its timer and controls may need setting again. A code on the display says what the boiler found. Pick "Fault checker" under "I need help with" at the top of this page, then your make and the code.
2. Is the hot water switched on?
The programmer or timer should be in an "on" period for hot water. Check its time, its date and its batteries too. A power cut can reset a timer, and a clock not changed when the hours go forward or back comes on at the wrong times. Some boilers switch the hot water on and off at the boiler itself, as a Greenstar's hot water button does. The hot water temperature should be turned up too.
3. What does the pressure gauge read?
Pressure that is too low, or too high, makes the boiler switch itself off, and then the hot water stops. Most user guides ask for about 1 to 1.5 bar with the boiler cold. Below that, top up as your guide shows. The F22 fault code page covers Vaillant and Glow-worm, and the E119 fault code page covers Baxi and Potterton. Pressure that won't hold is a fault to ring about.
4. Is water reaching the taps?
No water from any tap, hot or cold, points to the supply, not the boiler. Ask your water provider, or wait for the supply to come back. See that the cold water main is turned on, too. A combi needs that supply to make hot water at all.
5. Is it freezing outside?
A frozen condensate pipe shuts the boiler down in a frost. Follow the white plastic pipe from the boiler to where it leaves the house. If it's frozen where you can reach it at ground level, thaw it with warm water, never boiling. Then reset the boiler as your guide shows. When a boiler won't fire up, and frozen condensate pipes.
If these checks don't bring the hot water back, stop there and ring a Gas Safe registered engineer. Calls to us are answered 24 hours a day.
Sources: the no hot water pages of Vaillant, Glow-worm and Viessmann, Alpha's FAQ, and the user guides of Worcester Bosch, Alpha and Ideal.
When it needs an engineer
No hot water needs an engineer once the checks above haven't brought it back, or as soon as you see any of these:
- A code on the display that comes back after the resets your guide allows.
- Lukewarm taps with warm radiators, or hot water that comes when the heating is on and not otherwise. The makers give both as signs of a stuck diverter valve.
- Hot water that isn't as hot as it was. Biasi's guides point to limescale or dirt in the hot-water heat exchanger.
- A cylinder that stays cold with the hot water on and its thermostat set right. Ideal points to a zone valve.
- Pressure that keeps falling, so the boiler keeps stopping. A boiler that keeps losing pressure has a leak or a failed part to find.
- Anything further would mean taking the casing off.
If you smell gas, leave the boiler alone and open the gold "Smell gas?" bar on this page, which gives the free emergency number. Otherwise, ring us, as finding why the hot water has stopped is our Gas Safe registered engineers' job.
Sources: Vaillant's and Glow-worm's pages on no hot water and the diverter valve, Biasi's Dina and Basica Cond manuals, Ideal's boiler FAQs, and Vaillant's page on losing pressure.
What changes the price of the fix?
The cost of getting the hot water back depends on its cause. A setting put right or a frozen condensate pipe may need no part at all. A diverter valve or a hot-water heat exchanger is a part to fit. Before an engineer comes out, the rate is agreed on the call. No work is done until you say yes. What changes the price is set out in how our rates work.
Do you cover my part of London?
Yes: we fix hot water faults all over Greater London, day and night, in every borough north and south of the Thames. Pick your side of the river to see the areas.
North of the river
Every borough north of the Thames: Barnet and Enfield at the top, Hillingdon in the west, Havering in the east, and central London in between.
South of the river
Every borough south of the Thames: Richmond and Kingston in the west, Bexley in the east, and down through Croydon to Sutton and Bromley.
Questions about losing hot water
Is losing hot water an emergency?
Losing hot water is a reason to ring us now. No heating or hot water is on our list of boiler emergencies to ring about straight away. You don't have to work out how urgent it is. When you ring, say what the boiler is doing, and we decide with you how soon an engineer needs to come.
Why is there hot water but no heating?
Hot water with no heating is the opposite fault. Once the heating's switch, timer and thermostat are checked, Vaillant names a diverter valve stuck on the taps as a cause on a combi. Our page on boiler repairs sets out the signs of each fault, this one included.
Could it be the cylinder, not the boiler?
Yes, a hot water cylinder can be the cause. A cylinder heated by the boiler depends on its own valve and thermostat, and either can fail while the boiler is fine. Our engineers repair the whole system, cylinders included. The valves and controls are explained on our page on heating repairs.
How much does it cost to fix?
Fixing no hot water costs more or less depending on its cause, and on any part it needs. The rate is agreed on the call before an engineer comes out. See how our rates work.
Don't know what has failed? You don't have to.Ring and say what you can see or hear. Finding the fault is our job.
Calls answered 24 hours a day
A real person answers and gives you the rate on the call. No work starts until you say yes, and repairs are guaranteed for 12 months: parts, labour and any return visit.
