E14 displayed, no hot water, expansion vessel may be waterlogged

Safety: Pressurised hot water systems can be dangerous. Only work on the expansion vessel and safety valves if you understand unvented system regulations. Otherwise, call a G3‑qualified engineer.

Checks:

• Visual inspection: Look at the expansion vessel (often red or white, mounted near the cylinder). If it feels heavy and full of water when tapped, the diaphragm may have failed.
• Check air charge: With the system depressurised and cold, measure the air pressure at the Schrader valve on the vessel using a tyre gauge. Compare with the label (commonly around 3 bar for mains‑pressure units). Re‑pressurise with a pump if low.
• Connection check: Ensure the pipe between the vessel and the cylinder is not blocked or isolated by a closed valve.
• PRV inspection: If the pressure relief valve is constantly dripping, it may be passing due to overpressure or contamination. Operate the test lever briefly to flush, but if it continues to leak, replace the valve.

Note: Any work on unvented Gledhill cylinders must comply with local regulations; in many regions, only certified engineers may adjust safety components.