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The taps run cold, the shower is freezing, and the boiler looks innocent on the wall. Most no-hot-water calls trace back to a handful of small causes — work the clock below before anyone is called out.
The one-line answer: if you smell gas, leave the house and call 0800 111 999 — that comes before everything. Otherwise check the boiler pressure (around 1 to 1.5 bar cold), the thermostat and timer, and the fuse board, then ring 020 4577 2888 to be connected with a local plumber, any hour.
Stand at the boiler and smell. Any hint of gas, and this stops being a hot water problem: leave the property, touch no switches or flames, and call the National Gas Emergency Service on 0800 111 999 from outside. No gas smell? Then look for the dull explanations first — a boiler display that has gone completely dark usually means a tripped switch or fuse at the consumer unit, not a dead boiler, and flipping the circuit back on has ended plenty of cold showers.
Nothing here is dangerous yet — it is just cold water. Carry on down the clock.
Now collect the easy facts. The pressure gauge should sit around 1 to 1.5 bar with the system cold; a needle well below that means the system has lost water, and topping up once through the filling loop — following your manual, closing the loop properly afterwards — may bring everything back. Then the controls: a thermostat nudged down, a timer or smart schedule scrambled by a power cut, a clock still on the wrong hour after the change. It is unglamorous, but a boiler waiting politely for its schedule looks exactly like a broken one.
On a frosty central-Scotland morning, add one more check: the condensate pipe, the small plastic pipe running outside. If it has frozen, the boiler shuts down with a fault code, and pouring warm — never boiling — water along a reachable section at ground level, then resetting once, often clears it.
The next clue is what kind of hot water your house makes. If you have a combi and the radiators heat up while the taps run cold, that split points at the diverter valve inside the boiler — a known fault, and strictly an engineer's job. If you have a hot water cylinder, you carry a spare: the immersion heater, an electric element with its own switch, can heat a tank of water while the boiler sulks. And if one tap splutters and coughs while others run fine, suspect an airlock in that run rather than the boiler at all.
What you do not do, at any point, is open the boiler casing. Everything behind it belongs to a Gas Safe registered engineer, and nothing behind it will get your shower hot sooner tonight.
Ring with the pressure reading, any fault code written down exactly, and what you tried. That is most of the diagnosis done before the van moves. You will get an honest sense of arrival time based on workload and distance, an honest opinion on whether this is a tonight job or a tomorrow job, and you can ask about the call-out fee and hourly rate before agreeing to anything. While you wait, an immersion heater or electric shower may still give you hot water by another route — a cold evening is uncomfortable, not unsafe.
Once the hot water is back, note what failed and when — a boiler that needs topping up weekly or resetting daily is telling you something is wrong underneath, and the pattern sells the diagnosis. Label the filling loop and the immersion switch while you remember where they are, and if the condensate pipe froze, ask about insulating or rerouting it before the next cold snap.
That split — heating fine, taps running cold — is the classic sign of a sticking diverter valve, the part inside a combi that switches between heating and hot water. It sits behind the casing, so it is a job for a registered engineer, not a homeowner. Mention the exact symptom when you phone; it tells the plumber most of the story before they arrive.
Usually yes, once. Most sealed systems have a filling loop underneath the boiler, and your manual shows the steps for your model. Aim for roughly 1 to 1.5 bar with the system cold and close the loop fully afterwards. If the needle keeps sliding back down over the following days, stop topping up and have the leak traced instead.
No. Everything behind the casing is for a Gas Safe registered engineer, and nothing behind it will bring your hot water back sooner tonight. The safe householder moves all happen outside the casing: the pressure gauge, the filling loop, the thermostat and timer, the reset button and the fuse board. If you smell gas at any point, leave the property and call 0800 111 999 from outside.
It is an electric backup element inside the cylinder, usually with its own labelled switch nearby. If the boiler is down, switching the immersion on can give you a tank of hot water within an hour or so while you wait for the repair. If it does nothing, check its switch and the fuse board — a tripped circuit is a common quiet culprit.
The main page — the whole first hour on one clock, plus areas covered.
Go to home →Pressure, lockouts, frozen condensate pipes — and gas safety first.
Start the clock →Stopcock in the first minute — the timed plan for water everywhere.
Start the clock →Gentle heat from the tap end — and the lagging that stops the next one.
Start the clock →Damp patches and dropping pressure — the honest stopcock test.
Start the clock →One plughole or the whole house — how to tell, and what to try.
Start the clock →Honest ballparks and the questions to ask before work starts.
Read the guide →Ring any hour with the pressure reading and what you tried, and be connected with a local plumber covering Dunfermline and west Fife.
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