No Hot Water From Your Boiler? What It Might Be May 27, 2026 Standing at the sink with cold water coming from the hot tap is never a good start to the day. Whether you have a combi boiler or a system boiler with a hot water cylinder, there are a few simple checks you can carry out yourself before calling an engineer. These quick steps might save you time and money. However, it’s also important to recognise clear signs when it’s best to get professional help straight away to avoid further damage or safety risks. In this guide, we’ll walk you through what to look for and what actions to take. First checks when there is no hot water Before assuming the boiler itself has failed, it is worth ruling out a few basic issues. These quick checks are safe for most homeowners and can save time when you do speak to an engineer. Start by trying more than one hot tap or shower, ideally on different floors. If one outlet is cold but others are hot, the problem may be with that tap or mixer rather than the boiler or cylinder. Check other hot taps and showers to see if all are affected Look at the boiler display for warning lights or error codes Confirm the gas supply is on and other gas appliances work Make sure the programmer or timer is set to provide hot water If you have a hot water cylinder, feel the side of the cylinder near the middle using the back of your hand. It should feel warm if it has been heating recently. Take care not to touch any bare metal pipes that might be very hot. Programmer and thermostat settings Incorrect settings are one of the most common reasons for no hot water, especially after a power cut or when clocks change. On combi boilers, the hot water is usually on demand, but there may still be a hot water mode that can be turned off accidentally. On a system boiler with a cylinder, check the programmer or wall-mounted controller. Ensure the hot water channel is set to "on" or "timed" and that you are actually within an on period. Try pressing the boost or advance button to see if the boiler starts. The cylinder thermostat should normally be set around 60 °C. If it is turned too low or has failed, the boiler may not be told to heat the water. Do not open the wiring cover or attempt electrical work yourself; simply note the setting and mention it to your engineer. Low pressure on combi and system boilers Most sealed systems rely on the correct water pressure to operate. If the pressure is too low, the boiler may lock out and provide neither heating nor hot water. Look at the pressure gauge, usually on the front of the boiler or just underneath. When the system is cold, many domestic boilers are designed to run around 1.0 to 1.5 bar. If the needle is near zero or flashing low, that is likely to be your problem. Some homeowners are comfortable using the filling loop to top up pressure, following the manufacturer’s instructions. If you are unsure, it is safer to leave it and call a professional, especially if the pressure keeps dropping, which can point to a leak. Heating works, but hot taps are cold If your radiators get hot but the taps and shower stay cold, that is often a sign of an issue with a diverter valve on a combi boiler. The diverter valve switches heat between the central heating and the hot water demand. Typical symptoms include hot radiators whenever you run a hot tap, or the boiler firing briefly for hot water, then cutting out. The fix usually involves repair or replacement of the valve, which needs a Gas Safe registered engineer. On a system with motorised valves near the cylinder, a stuck or failed valve can cause similar behaviour. You might hear the boiler running, but find the cylinder never heats properly. Frozen condensate pipe in cold weather In freezing conditions, a blocked or frozen condensate pipe can stop a modern boiler from working. The condensate pipe is often a small white or grey plastic pipe running from the boiler to outside. If this pipe is frozen, the boiler will usually lock out with an error code and may make a gurgling noise. You can gently warm the external pipe using warm (never boiling) water from a jug or by applying a warm cloth, then try one reset once the ice has cleared. Do not use kettles of boiling water, open flames or tools to chip off the ice. If you are at all unsure that you have identified the correct pipe, leave it to an engineer. Ignition, flame failure and lockouts If your boiler tries to start, clicks several times and cuts out, or shows a flame failure error, there may be an ignition issue. Causes range from a blocked burner to a faulty sensor. First, check that the gas supply is on and that any gas hob or other appliance is working normally. If everything else seems fine, you can try a single reset according to your boiler manual. If the boiler locks out again or repeatedly needs resetting, stop trying to restart it. Repeated lockouts are a clear sign that a professional needs to diagnose the underlying fault. Scale and sludge reducing hot water performance In hard water areas around Hampton, Twickenham and Walton on Thames, limescale can build up inside a combi boiler’s plate heat exchanger. This restricts water flow and heat transfer, so you may get lukewarm water that runs hot then cold. Sludge from corrosion in radiators can also affect system boilers and cylinders. It settles in pipework and heat exchangers, so the boiler works harder but less heat reaches your hot water. Signs include noisy operation, kettling sounds, slow-to-heat radiators and inconsistent hot water temperatures. Solutions often involve descaling, powerflushing or fitting filters, which are jobs for a trained engineer. Red flags that mean call an engineer now Some situations should never be ignored or treated as DIY projects. If you notice any of the following, turn the boiler off and seek help from a Gas Safe engineer immediately. Smell of gas around the boiler or meter Repeated lockouts or a constant need to reset the boiler Visible leaks from the boiler, pipes or cylinder Loud banging, knocking or kettling noises from the boiler Error codes that remain even after a single reset Always put safety first. If you suspect a gas leak, turn off the gas at the meter if safe to do so, ventilate the property and follow official emergency advice. FAQ: common questions about no hot water Can I reset my boiler to get hot water back? You can usually attempt one reset using the button or control shown in your manual. If the boiler trips again or shows the same error, do not keep resetting it. This points to a fault that needs professional attention. Should I turn the boiler off if I have no hot water? If the boiler is displaying an error code, making unusual noises, or you can see leaks, it is sensible to turn it off until an engineer has checked it. If it is simply not firing at all and there are no warning signs, you can leave the power on while you wait for a visit. Is it safe to use the heating if there is no hot water? Sometimes a fault only affects the hot water side, for example, with a diverter valve. If the boiler is otherwise running normally with no error messages, it may be safe to use the heating. If you are unsure, an engineer can advise after inspection. Arrange boiler help in Hampton and nearby areas If you still have no hot water after these checks, it is time to bring in a professional. A trained engineer can test gas pressures, sensors, valves and controls to pinpoint the fault safely. Solve Heating Services Ltd provides Gas Safe registered boiler diagnostics, repairs and servicing across Hampton, Twickenham and Walton on Thames. We take care to work cleanly in your home, protect your flooring and tidy up properly when the job is done. To get your hot water back on and keep your boiler running reliably, contact Solve Heating Services Ltd on 07919959893 to arrange a convenient appointment.
