No Hot Water Coming From Your Taps?

The symptom can show up in different ways, and the difference is a useful clue. Some people turn on the hot tap and get no water at all. Others get a strong flow that simply stays cold. Some find the hot tap works in the kitchen but not in the bathroom, or that water runs warm for a few seconds before turning cold. Before you start checking anything, note which of these you have, whether the heating still works, and whether the cold taps are running normally.

If the cold taps are also weak or dry, the problem is probably the mains water supply rather than your boiler or cylinder. If only one hot tap is affected, the fault is likely in that tap or its section of pipe. If every hot tap is cold but water flows freely, the heat source or the controls that direct heat to your hot water are the most likely culprits.

A combi boiler heats water on demand as it passes through, so there is no tank to run out. When a combi gives no hot water, the first thing to look at is the boiler display. A fault code or flashing light means the boiler has locked out for safety, often because of low pressure, an ignition problem or a blocked condensate pipe in cold weather. Your manual explains what the code means and whether a reset is safe.

The diverter valve is the next common cause. It switches the boiler between heating the radiators and heating the taps. If it sticks, you may find the radiators get hot while the taps stay cold, or the hot water only comes through lukewarm. A sticking or failed diverter valve needs a Gas Safe engineer to diagnose and replace it, because it sits inside the boiler casing.

Combis also need enough incoming water pressure to fire. If the mains supply has dropped, perhaps because of work in your street, the flow sensor may not detect enough water to start heating. Airlocks in the hot pipework after recent plumbing work can produce spluttering, then no flow at all.

Homes with a hot water cylinder, often in an airing cupboard, store heated water rather than making it on demand. If the stored water is cold, check the cylinder thermostat, a small dial strapped to the side of the tank. If it has been turned down or has failed, the boiler will not be asked to heat the cylinder.

Many cylinders also have an immersion heater as a backup or main heat source. A tripped fuse, a switched-off isolator or a failed element will stop it heating. If the hot taps give no water at all on a vented system, the cold water storage tank in the loft may be empty, or an airlock may be blocking the pipe from the cylinder.

System boilers heat an unvented or vented cylinder through a motorised valve. When the valve motor or its microswitch fails, the valve can stay closed to the hot water circuit, so the cylinder never heats even though the boiler runs for the heating. The cylinder thermostat can cause the same symptom if it does not call for heat. Check the programmer too: a hot water schedule set to “off” or knocked out by a power cut is a surprisingly common cause.

Start with the simple things. Check that the boiler has power and that the programmer or app shows hot water as on. Look at the pressure gauge on the front of the boiler: most sealed systems should read between roughly 1 and 1.5 bar when cold. Note any fault code and look it up in the manual, and only use the reset button once if the manual says it is safe. In freezing weather, a frozen condensate pipe outside is a common cause of lockout on modern boilers.

On a cylinder system, check the cylinder thermostat setting, the immersion switch and its fuse. Run each hot tap in turn to see whether the problem affects one outlet or all of them. Do not open the boiler casing, remove covers from gas appliances or attempt to free a diverter or motorised valve yourself. If you smell gas, leave the property and call the National Gas Emergency number on 0800 111 999 straight away.

Call a Gas Safe registered engineer if the boiler shows a fault code that will not clear, keeps losing pressure, makes unusual noises, or if the radiators heat but the taps stay cold. These symptoms point to internal components, and any work inside a gas boiler must be carried out by a registered engineer by law. An electrician or qualified plumber can deal with immersion heater wiring and element replacement.

When you book, it helps to say what type of system you have, the boiler make and model, any fault code, and whether the heating still works. That lets the engineer bring likely parts and reduces the chance of a second visit.

The cost depends on the cause rather than the symptom. A reset, repressurising or a programmer setting takes minutes, while a diverter valve, motorised valve or immersion element involves parts and more labour. Other factors include the age and make of the boiler, whether parts are in stock, how easy the appliance is to reach, and whether the visit is planned or an emergency out of hours. Ask for the hourly rate and any parts costs to be confirmed before work starts.