Hot water problems
Hot Water Problems
First decide whether the fault is the whole house or one outlet. No hot water anywhere, with the radiators still warm, usually points to the combi boiler’s diverter valve or hot water sensor. One cold shower or tap is a local fault. A cylinder that has gone cold points to the immersion, the programmer or the motorised valve.
No hot water from a combi boiler
Run the hot tap fully open for a minute. A combi only fires when it senses water flowing, so a trickle from a furred tap may not start it. Then check the display for a code and the gauge for roughly 1 to 1.5 bar, because low pressure stops hot water as well as heating.
If the radiators work but the taps run cold, read heating on but no hot water. The usual culprit is the diverter valve, which switches the boiler between heating and taps. Brand guides cover Worcester, Vaillant and Baxi boilers, where the controls and common faults differ.
Hot water that turns cold after a minute, or only ever lukewarm, is its own set of faults. Start with hot water runs cold after a minute.
One tap or the shower only
If the kitchen tap is hot and the shower is not, the boiler is fine. Thermostatic mixer showers often fail at the cartridge, and a partly closed isolation valve on one pipe gives weak or cold flow. See no hot water in the shower only and low hot water pressure at one tap.
Cylinder and immersion heater faults
Homes with a hot water tank rather than a combi often have two ways to heat it: the boiler and an electric immersion. If the boiler side has failed and an immersion is fitted, it is your backup tonight. If the immersion has stopped, check its wall switch is on and its breaker at the consumer unit has not tripped, then read immersion heater stopped working.
Water dripping from a cylinder or pouring from a tundish on an unvented system needs attention the same day. Switch off the boiler and the immersion and see hot water tank dripping.
Never cap or block a tundish or relief pipe that is discharging water. It is releasing pressure for a reason.
Getting no hot water fixed tonight
A no hot water repair visit is the £60 call-out at any hour. The engineer confirms whether it is the diverter valve, a sensor, the flow switch or a controls fault, and the repair price is agreed with you on site before any work starts. Gas work is carried out by Gas Safe registered engineers.
Renting? The fix is your landlord’s to arrange, and tenant rights with no hot water covers what to ask for and how fast.
Emergency repairs
Guides
- Baxi Boiler No Hot Water
- Boiler Not Heating Water: What to Check First
- Combi Boiler Hot Water Not Working
- Heating On but No Hot Water: Combi Boiler Causes
- Heat Interface Unit Not Working: No Heating or Hot Water in Your Flat
- Hot Water but No Central Heating
- Hot Water Only Lukewarm From a Combi
- Low Pressure on the Hot Tap Only
- Hot Water Runs Cold After a Minute
- Hot Water Smells of Rotten Eggs
- Hot Water Tank Dripping: Is It Failing?
- Hot Water Tank Replacement Cost
- How to Drain a Hot Water Tank
- How to Reset an Immersion Heater
- How to Test an Immersion Heater Element
- How to Turn Off the Hot Water Supply From a Cylinder
- Immersion On but Still No Hot Water
- Immersion Heater Replacement Cost
- How Much Does an Immersion Heater Cost to Run?
- Immersion Heater Stopped Working: Fuse, Stat or Element?
- No Hot Water Coming Out of the Taps
- No Hot Water to the Shower Only
- No Hot Water From a Worcester Boiler
- Temperature and Pressure Relief Valve Explained
- No Hot Water in a Rented Home: Your Rights and Timescales
- Water Running Into the Tundish: Emergency or Not?
- Vaillant Boiler: Heating Works, No Hot Water
- Water Heater Working but No Hot Water
- What Does an Immersion Heater Do?
- Why Have I Got No Hot Water? A Quick Diagnosis
Questions people ask
Why have I got heating but no hot water on a combi?
The diverter valve is usually stuck in the heating position, or the flow sensor is not detecting the tap opening. Both are inside the casing, so they need an engineer.
I rent. How quickly should my landlord fix no hot water?
In England, landlords must keep the installations for heating water in repair under section 11 of the Landlord and Tenant Act 1985, so a total loss of hot water should be reported in writing and treated as urgent.