Boiler fault — London
No hot water in London?
Gas Safe registered engineers diagnose and repair no hot water faults across all London boroughs. Diverter valve faults, boiler ignition failures and pressure issues resolved — often same day.
Diagnosing the fault
Common causes of no hot water in London
No hot water, heating works
Moderate- Faulty diverter valve on combi boiler — stuck on heating
- Plate heat exchanger failure or blockage
- DHW thermistor (sensor) fault
- Flow rate sensor fault
No hot water and no heating
High- Boiler pressure too low — check gauge (should be 1–1.5 bar)
- Ignition lockout — boiler attempting but failing to fire
- Overheat thermostat tripped
- Gas supply interruption — check meter and other appliances
Hot water cold then warm intermittently
Moderate- Partially blocked diverter valve
- Scale on plate heat exchanger restricting flow
- Intermittent fault on temperature sensor
- Thermostatic mixing valve (TMV) fault
Hot water lukewarm but not hot enough
Low-moderate- Boiler temperature set too low — check boiler controls
- Scale build-up on heat exchanger reducing efficiency
- Failing boiler — reduced output due to age
- TMV set too conservative — legal minimum is 50°C at tap for Legionella control
London landlords
Legal duty to restore hot water in rental properties
Under Section 11 of the Landlord and Tenant Act 1985, landlords must maintain installations for the supply of water and heating. Loss of hot water is a breach of this obligation. We attend no-hot-water callouts at rental properties as a priority — same-day in most London boroughs.
Your boiler brand
We repair all major London boiler brands
Common questions
No hot water London: frequently asked
Why do I have no hot water but my heating works in London?
If your central heating works but you have no hot water, the most likely cause is a faulty diverter valve on your combi boiler. The diverter valve routes water to heating or hot water — when it sticks open on the heating side, hot water stops. Other causes include a failed plate heat exchanger or DHW sensor fault. A Gas Safe engineer can diagnose this in a single visit.
Why do I have no hot water and no heating in London?
Loss of both heating and hot water usually indicates a boiler fault — common causes include low boiler pressure (check the gauge, should be 1–1.5 bar), ignition failure (boiler attempting to fire but failing), a tripped overheat thermostat, or a gas supply interruption. Check if your gas meter has credit and if other gas appliances are working. Then contact a Gas Safe engineer.
How quickly can you fix no hot water in London?
We aim to attend no-hot-water callouts in London within the day. Loss of hot water is treated as a priority fault, particularly for rental properties where landlords have a legal obligation to provide hot water under Section 11 of the Landlord and Tenant Act 1985.
As a landlord, how quickly do I need to fix no hot water for my tenants?
Under Section 11 of the Landlord and Tenant Act 1985, landlords must maintain heating and hot water systems in working order. There is no specific time limit in statute, but case law and best practice suggests repairs should be made within 24 hours for loss of hot water. For vulnerable tenants, elderly occupants or young children, the obligation to act quickly is stronger.