A boiler not heating water can turn an ordinary morning into a stressful one. You may still have heating, hear the boiler running, or see no obvious fault at all, yet the taps remain cold. Before assuming the boiler needs replacing, there are a few safe checks you can make – and clear signs that it is time to call a Gas Safe registered engineer.
For households in Maidstone and across Kent, the priority is simple: restore reliable hot water safely, with as little disruption to home life as possible.
Start with the safe, simple checks
Not every hot-water problem is a major boiler fault. Occasionally, the cause is a setting, timer or water supply issue that can be identified without removing a boiler casing or touching any gas components.
First, check whether the boiler has power. Look at the display or indicator lights, check the fused spur near the boiler is switched on, and see whether a tripped circuit breaker has affected it. If the display is blank and the electrical supply appears to be on, do not attempt to open the appliance. An engineer can establish whether the issue is with the boiler, its controls or the electrical connection.
Next, look at the boiler pressure gauge if your system has one. Most sealed systems operate at around 1 to 1.5 bar when cold, although the correct range varies by boiler. Pressure that is very low can stop some boilers from operating properly. Your boiler manual may explain how to repressurise the system, but if pressure repeatedly drops, there may be a leak or a faulty component that needs professional attention.
It is also worth checking the controls. Make sure the hot-water setting is enabled, the programmer is set correctly and any room thermostat or smart control is not preventing operation. If you have recently had a power cut or changed the clocks, timer settings can sometimes be the answer.
Boiler not heating water but radiators are hot
When your radiators are warming up but the taps are cold, the fault is often within the boiler’s hot-water function rather than the whole heating system. This is common with combi boilers, which heat water on demand whenever you open a hot tap.
A diverter valve is one possible cause. This component directs heated water either to the radiators or to the hot-water supply. If it becomes stuck or fails, the boiler may continue to heat the central heating while failing to provide hot water. This is not a safe DIY repair and usually requires diagnosis and replacement by a qualified engineer.
Another possibility is a faulty flow sensor, thermistor or heat exchanger issue. These parts help the boiler recognise that a tap has been opened, monitor water temperature and transfer heat effectively. Limescale can contribute to problems in hard-water areas, particularly where hot-water performance has gradually worsened rather than stopped suddenly.
If your boiler makes unusual banging, whistling or kettling noises, switches itself off, or produces water that alternates between hot and cold, arrange an engineer visit. Continuing to reset the boiler may not solve the underlying fault and can delay a proper repair.
No heating and no hot water
If neither the heating nor hot water is working, begin with the basic checks above, then look for an error code on the boiler display. Write the code down, along with the boiler make and model, before contacting an engineer. This information can help make the first visit more efficient.
A loss of pressure, frozen condensate pipe during cold weather, faulty pump, ignition fault or problem with the gas supply can all affect both services. Some boilers can be reset once using the manufacturer’s instructions. If the fault returns, avoid repeated resets and arrange a professional inspection.
Check whether other gas appliances, such as a gas hob, are working as expected. If you suspect a gas supply issue, smell gas, notice a damaged gas pipe or feel unwell with symptoms such as headaches, dizziness or nausea, turn off the gas supply only if it is safe to do so, open doors and windows, leave the property and seek urgent advice from the gas emergency service. Do not operate electrical switches, smoke or use a naked flame.
Why hot water may be weak, lukewarm or inconsistent
A boiler fault is not always an all-or-nothing problem. Lukewarm water, poor flow or temperature changes during a shower can point to several different causes.
With a combi boiler, opening more than one hot tap at once can reduce flow and affect temperature. Combi boilers have a stated hot-water flow rate, so a busy household with two bathrooms may find that demand exceeds what the appliance can comfortably deliver. This is not necessarily a fault, but it may mean the system is no longer the best match for the home.
Low mains water pressure, a partially closed stopcock, blocked tap aerators or a shower valve problem can also make hot water seem unreliable. If hot water is poor at one outlet only, the issue may be local to that tap or shower rather than the boiler. If every hot outlet is affected, a boiler or wider plumbing inspection is more likely to be needed.
For homes with a conventional or system boiler and hot-water cylinder, check that the cylinder thermostat and programmer are set correctly. A failed motorised valve, immersion heater fault or cylinder thermostat problem may prevent the stored water from heating even if the boiler itself is operational.
What not to do when hot water stops
It is understandable to want a quick fix, particularly with children in the house or during colder weather. However, boilers contain gas, combustion components, electrical connections and pressurised water. Removing the casing, adjusting internal valves or attempting to repair components without the right qualifications can be dangerous and may invalidate warranties.
Avoid using the boiler if you see signs of a leak around the appliance, smell gas, notice soot or staining, or receive a carbon monoxide alarm warning. A carbon monoxide alarm should never be ignored, even if you feel well. Leave the property, get help and do not re-enter until it is safe.
You should also avoid relying on temporary workarounds for too long. A small leak or intermittent fault can become more disruptive, and a boiler that is losing pressure repeatedly needs a proper investigation rather than continual topping up.
When to call a Gas Safe registered engineer
Call an engineer promptly if you have no hot water, the boiler is showing a persistent fault code, pressure keeps falling, or the appliance is making unfamiliar noises. You should also arrange help where hot water is inconsistent, the boiler is leaking, or your heating works but hot water does not.
A professional visit should begin with clear diagnosis rather than guesswork. The engineer can check the boiler, controls, system pressure, safety devices and relevant plumbing connections, then explain the problem in plain English. From there, you can make an informed decision about repair, servicing or replacement.
At Dacey Heating Engineers, our approach is to assess what your household actually needs, explain the available options clearly and carry out work with care for your home. With more than 25 years of hands-on experience, we know that dependable hot water is not a luxury – it is part of everyday comfort.
Preventing future hot-water problems
Annual boiler servicing is one of the most practical ways to reduce the chance of an unexpected loss of hot water. A service helps identify worn components, pressure concerns, combustion issues and developing faults before they leave you without heating or hot water.
It also helps to pay attention to early warning signs. A boiler that takes longer to heat water, needs frequent repressurising, makes new noises or delivers fluctuating shower temperatures is worth checking before a complete breakdown occurs. Keeping the boiler manual accessible and noting the make, model and installation date can also save time if you need support.
If your boiler is older, frequently repaired or struggling to meet household demand, replacement may be more economical over time. That decision depends on the appliance’s condition, repair cost, energy efficiency and how your family uses hot water. A local heating engineer can talk through the trade-offs without pushing a one-size-fits-all answer.
Cold taps do not always mean a major emergency, but they do deserve the right response. Make the safe checks, avoid opening the boiler yourself, and arrange experienced help if the problem persists – so your home can get back to feeling comfortable and cared for.
