Expansion Vessel Replacement

What expansion vessel replacement covers

A targeted visit to diagnose the fault, replace the vessel (or internal bladder type where applicable), and return the hot water system to safe, stable operating pressure.

• Fault diagnosis to confirm the expansion vessel is the cause, not a pressure reducing valve or safety valve issue
• Isolation and safe depressurisation of the hot water circuit
• Correct sizing and selection of a suitable expansion vessel and fittings
• Replacement of the vessel and any perished hoses, valves, or connection parts needed to complete the job
• Recharge and pressure set-up to the manufacturer specification
• Checks for leaks and correct operation during heat up
• On unvented cylinders, verification of key safety components and discharge behaviour (work carried out by appropriately certified engineers)

When this service is the right fit

This is most relevant if you notice repeated discharge from the tundish, pressure relief valve dripping, rapid pressure changes on the gauge, or banging and water hammer as the system heats. It is also common after a cylinder service highlights a waterlogged vessel or a split diaphragm. Landlords and commercial sites often choose replacement to reduce call-outs and protect fittings from ongoing strain.

What happens during the visit

The system is assessed first, then isolated and depressurised so the vessel can be safely removed. The new vessel is installed, charged to the correct pressure, and the system is refilled and tested while heating to confirm pressures remain stable. If access is limited or the vessel is located remotely from the cylinder, the approach and any alternatives are discussed before work proceeds.

Aftercare and ongoing value

Once replaced and set correctly, you should see steadier pressure and little to no discharge during normal heat up. If your system is unvented, routine servicing helps keep safety devices, pressure settings, and discharge pipework working as intended. Any follow-up recommendations are kept practical, based on what is seen on site.