No hot water and no heating? Check these first
When you have no hot water and no heating at the same time, the fault almost always sits at the boiler end of the system, because the boiler is the one thing both jobs share. Several of the most common causes take a few minutes to put right without tools or an engineer, and working through them in order costs you nothing. If you reach the end of this list without success, you will at least be able to tell whoever you call exactly what the boiler is and is not doing, which makes the diagnosis quicker.
Start at the pressure gauge
Look at the gauge on the front or underside of the boiler. On most sealed systems the needle should sit between 1 and 1.5 bar when the system is cold. If it has dropped to zero or close to it, the boiler has locked itself out to protect the pump, and no amount of pressing reset will bring it back until the pressure is restored. Topping up is a safe job: open the two small valves on the braided filling loop under the boiler, watch the needle climb to about 1.2 bar, close both valves, then reset. If the pressure falls again within days, that is a separate problem worth investigating.
Rule out the controls
A boiler cannot fire if nothing is asking it to. Check the room thermostat first: turn it well above the current room temperature and listen for a click, then for the boiler starting up. Dead batteries in a wireless thermostat are a classic cause of a silent boiler, and so is a smart thermostat that lost its connection after a router change. Then check the programmer or timer. A power cut can wipe its schedule or knock it back to a default, so the boiler may simply believe it is the middle of the night. Set everything to constant or manual while you test.
In freezing weather, check the condensate pipe
Modern condensing boilers drain a small amount of water through a plastic pipe, often out through an outside wall. In a hard frost that pipe can freeze solid, the boiler shuts down, and you will usually see an error code and sometimes hear a gurgle. The safe thaw method: pour warm water, never boiling, along the frozen section of the external pipe, or hold a hot water bottle against it. Only do this if the pipe is reachable from the ground. Do not climb ladders in icy weather for a boiler. Once thawed, reset the boiler. If it happens every winter, an engineer can insulate or reroute the pipe so it stops.
Check the boiler has power
A completely blank display means no electricity, not a broken boiler. Check the fused spur switch next to the boiler, which gets switched off by decorators and cleaners, then check the consumer unit for a tripped breaker or RCD. If a fuse trips again immediately after you reset it, leave it off and call an engineer, because something is failing electrically.
When it is not the boiler at all
If you have a gas hob, try it. If no gas appliance in the home works, the problem may be the supply: a prepayment meter out of credit, or an outage in the street. If you smell gas at any point, stop and call the National Gas Emergency Service on 0800 111 999 first, before anything else, and only then arrange the repair with a Gas Safe registered engineer. And if you live in a block with communal heating, the fault may be in the plant room rather than your flat, so it is worth asking a neighbour before booking anyone.
Emergency call out or a booked visit
Call for an emergency visit if there are young children, elderly or unwell people in a cold home, if the failure comes with a leak, or if the weather is below freezing and nothing on this list has worked. Our office answers around the clock, 365 days a year, and gives you an arrival window. If the house is safe and merely inconvenienced, a booked repair visit is the better value: the first hour covers the call out and finding the fault, and after that the visit is charged by the hour, with any return visit or further work quoted first.
The short version
No hot water and no heating together usually means low pressure, a control that is not calling for heat, a frozen condensate pipe or a tripped switch, and all four are safe to check yourself. Anything involving gas, repeated electrical trips or a boiler that still will not fire belongs with an engineer.
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