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Boiler Leaking Water: Is It Dangerous? What To Do First (London) | ARA Services

Boiler leaking water —
is it actually dangerous?

This is usually how it goes: you open the cupboard, see a wet patch, and your brain instantly starts doing maths. “Is that a tiny drip… or is this about to soak the floor?” Some boiler leaks are manageable for an hour while you organise help. Others need you to switch off and stop guessing. I’ll tell you the difference in plain English — no scare stories, no waffle.

Emergency boiler guidance Call 07727 154746 Start the safety steps

If your leak comes with no heating or no hot water, use this quick checklist first: what to do when the boiler stops giving heat.

Written by Abdul — Gas Safe Engineer (ID: 626557)
ARA Services Ltd (Plumbing and Electrical Services) • Open 24 hours • London and nearby areas
Gas Safe Registered Emergency call-outs East & North London 5.0★ (34 Google reviews)
NAP: Durning Hall, Suite 14, Hyat Hub 14, Earlham Grove, London E7 9AB • +44 7727 154746
If water is near electrics, treat it as urgent. If you can see water running onto plugs, a fused spur, wiring, or the floor is getting properly wet under the boiler — don’t “test it one more time”. Switch the boiler off (only if safe), keep hands dry, and call. If you want a clear triage route, use: the emergency decision checklist.

Is a boiler leak dangerous? The honest answer

It can be — but danger usually comes from what the water is touching, not the water itself. A boiler has hot water, pressure, gas components and electrics all packed together. Water in the wrong place can trip electrics, corrode connections, or cause a short. (And yeah… sometimes it also wrecks the kitchen unit underneath. Seen that more times than I can count.)

Proper “London reality” detail: lots of flats have boilers squeezed into hallway cupboards. When it leaks, it doesn’t drip into an empty plant room — it drips onto shoes, laminate, and whatever’s stored under there. People wipe it, hope it behaves, go to bed… then wake up to a lockout and wet flooring. That’s the pattern.

Lower-risk leak (still needs fixing, but you’re not in a sprint)

A slow drip from an external joint, a visible pipe connection, or a small damp patch that isn’t spreading fast.

What I usually advise: turn it off if you’re unsure, protect the area, take photos, then book a repair before it worsens.

Higher-risk leak (treat as urgent)

Water appearing from inside the boiler casing, water near wiring/electrics, or rapid dripping/pooling.

If you can’t tell whether it’s coming from inside the unit, assume worst-case and follow the urgent route.

The sneaky signs of a “hidden leak”

Pressure dropping repeatedly, damp cupboard backs, swollen skirting, a musty smell near the boiler, or random lockouts.

If pressure keeps falling, don’t keep topping up forever — read: why boiler pressure keeps dropping.

What to do in the first 5 minutes

I’m not going to tell you to “stay calm” — you’ll calm down after you’ve stopped the risk. Do this in order. It’s boring, but it works.

  • Look first: is the water outside the casing (pipes/joints), or does it look internal?
  • Keep hands dry: if water is near electrics, do not touch anything with wet hands.
  • Switch the boiler off: use the boiler power button or fused spur if safe to reach.
  • Contain the mess: tray/towel down, move anything that can get ruined.
  • Take 3 photos: leak area, pressure gauge, any error code.
  • Don’t remove covers: internal leaks are a qualified engineer job.
What NOT to do (common mistakes)
  • Don’t keep re-pressurising “to see if it holds”.
  • Don’t keep pressing reset if it starts failing — it’s not solving the leak.
  • Don’t wrap a towel around a hot joint and walk away — it hides the leak and soaks everything behind.
  • Don’t ignore damp “because it’s only a bit”. That’s how cupboards rot.
If you need a simple decision rule
  • Water near electrics = urgent.
  • Rapid dripping/pooling = urgent.
  • Slow external drip = book repair, but don’t ignore.
  • Not sure? Use a structured triage page.

Here’s the quick route: emergency boiler advice and next steps.

Why leaks show up at the worst times

Nine times out of ten, the leak shows itself when the boiler is working hard — first heating cycle of the morning, or the evening shower rush. Heat expands things. Pressure moves things. A joint that’s “barely holding” suddenly isn’t.

If your leak seems linked to pressure behaviour (fine cold, weird when hot), it’s worth reading this: what pressure loss usually points to.

Spotted water near the boiler? Let’s not let it turn into a flood.

If you’re in London and you’re unsure whether it’s safe to keep the boiler running, call us and describe what you’re seeing. We’ll tell you straight.

Scenario: if you’re in Forest Gate (E7) and the cupboard floor is wet under the boiler, call 07727 154746 and tell us whether the water is inside the casing or from a visible pipe joint.

What we do when we attend a leak (no mystery process)

A lot of people expect us to just tighten something and leave. Sometimes it genuinely is a joint — but we still check why it started leaking, whether pressure has been doing something odd, and whether the boiler is about to lock out again the moment it heats up.

  • Confirm whether the leak is external (pipework/joint) or internal (component inside the case).
  • Check pressure behaviour and look for signs of safety discharge events.
  • Inspect visible joints, pump area, condensate route, and staining that points to seepage.
  • Explain what failed in normal language and give options based on safety and value.

If the boiler is switching off and throwing codes, use this separate page: why boilers lock out (error codes explained).

If you want pricing ranges before you commit, see: typical boiler repair costs in London. And if you’re comparing engineers, this helps people avoid cowboys: how to choose a legit Gas Safe engineer.

Want a straight answer on whether it’s safe to keep it running?

Tell us where the water is, how fast it’s dripping, and what the pressure gauge shows. We’ll advise whether to shut it down immediately or book a repair.

If you’re near Stratford and the leak is actively pooling, call 07727 154746 and tell us if it’s coming from inside the casing or a pipe joint. That changes the urgency instantly.

Boiler leaking water — FAQs

Can I keep using the boiler if it’s leaking a little bit?

Sometimes — but only if it’s a small external drip and it’s nowhere near electrics. If you’re unsure whether the water is internal, switch it off and call.

What if the leak only happens when the heating is on?

That often points to pressure/temperature changes opening up a weakness. Check cold vs hot pressure. If pressure keeps dropping, it usually needs diagnosis — see why pressure loss keeps happening.

Should I top up the boiler pressure if it’s leaking?

Only as a short-term emergency to restore heat if you must and it’s safe. Repeated top-ups can worsen the situation. If you’re topping up often, book a repair.

My boiler keeps cutting out after I noticed damp — is that related?

It can be. Water and electrics don’t mix, and some boilers lock out for safety. If you’re seeing faults, read: lockouts and error code reasons.

How quickly can you attend a leaking boiler?

It depends on where you are and what’s already booked in, but we’re open 24 hours and we prioritise genuine urgent cases (water near electrics, rapid leaks, vulnerable households). If you’re unsure, call and describe it.