Boiler frequently loses pressure, requiring regular top-ups via the filling loop.

Safety first: Do not repeatedly overfill the system above the recommended pressure. Excessive pressure can cause leaks and damage.

Step-by-step checks:

• 1. Visual leak inspection: Check all visible pipework, radiators, valves, and the boiler underside for signs of dampness or staining.
• 2. Safety valve check: Inspect the discharge pipe from the safety valve (usually routed outside). If it is wet or dripping, the valve may be passing water.
• 3. Expansion vessel test: With the system cold and pressure at zero, briefly press the Schrader valve on the expansion vessel. If water emerges, the vessel has failed and must be replaced.
• 4. Monitor pressure: After topping up to 1.2 bar, note how quickly pressure drops. Rapid loss indicates a significant leak that must be located and repaired by a professional.

When to stop: If you cannot find a visible leak or if the expansion vessel is faulty, contact a heating engineer. Constant topping up introduces fresh oxygen and accelerates corrosion.