Is No Hot Water an Emergency? When to Call Tonight, and When It Can Wait

The quick test: emergency, same day, or book normally

Most people ask this question at night, standing next to a cold tap, trying to decide whether to pay for an out of hours visit. The honest split looks like this:

• Call now: the cylinder or boiler is leaking, the tundish is running hot water or steam, the hot taps have gone scalding, you can smell gas, or there is water near electrics.
• Call now: no hot water and no heating in cold weather, with a baby, an elderly person, someone unwell or someone with a medical need for washing or warmth in the property.
• Same day: no hot water at all, with no leak and nobody at risk. It is miserable, but nothing is getting worse by the hour.
• Book normally: hot water that is lukewarm, runs out quickly or takes longer to heat than it used to. These are real faults and worth fixing properly, but they are not urgent.

If you smell gas, do not use the phone call to us as your first step. Turn off the gas at the meter if you can, open windows, do not operate switches, and call the National Gas Emergency number on 0800 111 999.

When no hot water really is an emergency

The hot water itself is rarely the emergency. What matters is what else is happening. A cylinder that has stopped heating is an inconvenience. A cylinder that is overheating, leaking or discharging is a safety problem, and the fact that the taps have also gone cold is secondary.

Watch for hot water or steam coming from the tundish, the small funnel in the pipe below the cylinder valves. That means the temperature relief valve has opened, and the controls meant to stop the heating have failed. Switch the immersion and the boiler off, leave the valves alone, and call. Our guide to a hot water cylinder overheating explains what is happening and how to make it safe while you wait.

The other real emergencies are water escaping, from the cylinder, a pipe or the boiler, especially if it is heading for a ceiling below or anything electrical, and a loss of both heating and hot water in cold weather in a home where somebody vulnerable lives. A total loss of heating and hot water in cold weather is commonly treated as a twenty four hour matter by councils and letting agents, and for a family with a newborn that is exactly right.

Five checks worth doing before you call anyone

These cost nothing and take ten minutes. They are the same checks an engineer does first on arrival, so doing them yourself can save a visit altogether. Our full no hot water checklist before you call goes into each one.

• The programmer or timer. After a power cut, or when the clocks change, it can be sitting at the wrong time or with hot water set to off. Put it on constant or boost and wait half an hour.
• The boiler display. A fault code or a flashing light usually means a lockout. Note the code, then try the reset once. If it locks out again, stop and call.
• The boiler pressure, on a combi or system boiler. Below about 1 bar on the gauge and many boilers will refuse to fire.
• The immersion switch and its fuse or breaker, if the cylinder has one. A switch with no neon lit means no power is reaching it.
• In a freeze, the condensate pipe. A frozen plastic condensate pipe outside is a common reason a boiler locks out on the first cold mornings of the season.

How to get hot water tonight while you wait

If you have a hot water cylinder and the boiler has failed, the immersion heater is your backup. Switch it on at the wall switch next to the cylinder, and a full cylinder will be hot in a couple of hours. That is the main reason cylinders have one, as our page on what is an immersion heater explains. It costs more to run than gas, but for a night or two it is the obvious answer.

The reverse also works: if the immersion has failed and you have a boiler heated cylinder, set the programmer to heat the hot water. If the hot water has gone but the radiators still work, the fault is usually on the cylinder side, a motorised valve, a cylinder thermostat or a tripped cut-out, and our page on no hot water but heating works walks through it.

With a combi boiler there is no stored water and no backup, so if the boiler is down the hot water is down too. An electric shower, if you have one, runs independently of the boiler and will still work. Beyond that it is the kettle until the engineer arrives. Our page on no hot water from a combi boiler covers the usual causes, several of which you can clear yourself.

Tenants and landlords: who has to act, and how fast

If you rent, hot water is the landlord's repair, not yours. Report it in writing, by email or text, the same day, so there is a record of when they knew. Then let them or their agent arrange the engineer, unless the problem is dangerous and cannot wait.

If you are the landlord, treat a tenant with no hot water as urgent even when it is not an emergency. A few working days is reasonable for a partial fault, but a household with no hot water and no heating in winter should not be left waiting. Our page on landlord hot water responsibilities sets out what is required and how quickly. We can deal with the tenant directly for access and report back to you.

Why the first cold weeks bring the most calls

Every autumn, the week the heating goes back on is one of our busiest for no hot water calls. A boiler that has only been heating water all summer is suddenly asked to run the heating too, pumps and valves that have sat in one position for months stick, and expansion vessels and relief valves that were marginal start to show it. A motorised valve that seized over the summer is a classic reason the hot water only works when heating is on, or does not work at all. When both go at once, our guide to no heating or hot water narrows down what has failed.

If your hot water has been slow, noisy or temperamental over the summer, it is worth having it looked at before the first cold snap rather than after. It is cheaper to fix a fault in daylight with the right part on the van than on a freezing night when every engineer in London is busy.

Calling us out

When you call, tell us whether you have a combi boiler or a cylinder, what the boiler display shows, whether the heating works, and the make on the front of the boiler or the label on the cylinder. That is what lets the engineer arrive with the right part rather than coming back tomorrow. Our emergency plumber in London page explains how a call goes from there.

Our rate is fixed before we attend and does not rise for an evening visit or an awkward property; the pricing page sets it out in writing. We are 20 engineers across London working on hot water, heating and general plumbing. Call 020 4652 5111 or send an enquiry, and say whether anyone in the property is vulnerable so we can prioritise it.