Quick answer
Repeated boiler pressure loss, damp around radiators or pipe routes, corrosion and unexplained water are possible signs of a central-heating leak. Pressure loss can have other causes, so do not keep repressurising without finding out why it is happening.
Check for visible clues
Inspect accessible radiator valves, joints, boiler connections and pipework for drips, green or brown staining, corrosion or damaged flooring. A leak may be small or hidden under floors. Never remove the boiler casing; internal boiler work should be handled by a Gas Safe registered engineer where gas appliances are involved.
Understand pressure changes
A sealed heating system may need occasional pressure adjustment according to its instructions, but pressure that repeatedly falls needs investigation. Possible causes include a water leak, an expansion vessel issue or a pressure-relief component. Record the pressure when cold and any visible water, and follow the appliance manual rather than repeatedly topping up.
Take sensible precautions
- Switch off the heating if water is leaking onto equipment or causing damage, provided it is safe to do so.
- Keep away from wet electrical fittings and isolate the relevant circuit at the consumer unit only if safe.
- Do not touch hot leaking components or dismantle pipework.
- Arrange assessment by a suitably qualified heating professional.
When to call a plumber
- The boiler pressure keeps dropping.
- Water is visible around a radiator, boiler or heating pipe.
- A damp patch appears along a heating pipe route.
- The boiler shows a fault or you are unsure how to make it safe.