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No Heating or No Hot Water? What To Do First (London) | ARA Services

No Heating or No Hot Water?
A calm checklist to get you routed properly

This page is for the moment you realise you’ve got no heating, no hot water, or both. We’ll keep it simple: quick safety checks first, then the most common “what it might be”, then the correct next step.

Book a Gas Safe diagnosis Call +44 7727 154746 Emergency boiler guide
Boiler not firing? No hot water only? Boiler error codes

If you’re searching “boiler repair near me” in London — this page gets you to the right route fast without guessing.

Safety first (30 seconds) If you smell gas, a carbon monoxide alarm is sounding, you see soot/black marks around the boiler or flue, or anyone feels dizzy/sick in the property (especially if it improves outside), stop and use: boiler emergencies.

Step by step: what to check (in order)

We’re not doing DIY repairs here — just the safest checks that help confirm the likely cause and avoid wasted callouts.

STEP 1 Confirm what’s actually missing

Choose the closest match:

  • No hot water but heating works
  • No heating but hot water works
  • Both heating and hot water are out
If one of these matches exactly what you're seeing

These guides explain the likely cause in plain English and what normally fixes it.

Boiler pressure keeps dropping Radiator cold at the bottom Boiler making kettling / banging noises Radiators not heating upstairs

STEP 2 Check the boiler display for a fault code

A fault code helps diagnosis. If you see one, note it down. If the boiler repeatedly locks out, that’s a “stop guessing and book a diagnosis” situation.

STEP 3 Check pressure (only if you have a combi/system gauge)

Low pressure can cause lockout. If it drops again after topping up, that points to an underlying fault that needs a Gas Safe diagnosis.

STEP 4 Thermostat / timer sanity check

Make sure heating is being called for (timer on, thermostat above room temperature). If controls look wrong, don’t keep resetting the boiler repeatedly.

STEP 5 Look for visible leaks or damp near the boiler

If there’s any water around electrics, stop and treat it as an emergency route. If there’s no danger sign, it’s still a repair route — book diagnosis.

WHEN THIS BECOMES AN EMERGENCY

Escalate to emergency if you smell gas/burning, see soot marks, the CO alarm sounds, anyone feels dizzy/sick indoors, or there’s any sign of leaking near electrics. Use the emergency route above immediately.

District proof: Newham flats & terraces In Newham we often see older radiators, mixed pipework, and controls that have been changed over time. In flats, access and shared flues can also make breakdowns feel urgent — the key is checking for safety signs first, then booking a Gas Safe diagnosis rather than repeatedly resetting the boiler.
Stop DIY and call a Gas Safe engineer if: you smell gas/burning, see soot marks, the boiler repeatedly locks out, or there’s any sign of leaking near electrics.

Want a proper diagnosis (no guessing)?

If you’ve checked the basics and still have no heating or no hot water, a Gas Safe diagnostic visit is the fastest path to a real fix. London hard water can also accelerate sludge and scale issues, so repeated lockouts should be diagnosed properly.

FAQ

Is no heating and no hot water always an emergency?

Not automatically. It’s urgent, but usually a standard repair unless you also have gas/CO warning signs, soot marks, or water near electrics. If you’re unsure, use the emergency route.

Should I keep resetting the boiler?

A single reset can be reasonable, but repeated lockouts usually indicate an underlying fault that needs diagnosis. If the boiler repeatedly locks out, stop and book a Gas Safe repair visit.

What if I have hot water but no heating?

That often points to controls, diverter/valve behaviour, or circulation issues. Use the crisis sibling guides above or book a diagnosis for a proper fix.

What if I have no hot water only on a combi boiler?

Use: no hot water from a combi boiler for the fastest routing and next step.

Back to ARA Services If you want to see all services and routes, use: ARA Services homepage.

Written by Abdul (Gas Safe Engineer, 626557). For safety-critical boiler faults, always use a registered engineer.