A short guide to assist with servicing an Expansion Vessel on an Unvented Cylinder.
Perform a visual inspection of the Expansion Vessel looking for any signs of damage or corrosion. Remove the cap covering the schrader valve on the top of the vessel and check to see if air is present in the system (if you have water leaking from this point then the membrane may have failed)
To correctly test an Expansion Vessel you will need to isolate and remove the Expansion Vessel from the system. Isolate the mains incoming to the cylinder and drain water from a hot tap within the system to remove water within the Expansion Vessel
To accurately test the air pressure in the Expansion Vessel it needs to be removed from the live system, once removed you can connect a pressure gauge to the schrader valve. The Expansion Vessel pressure should be set in accordance with the manufacturers settings in their information guide, in most circumstances on a Potable System to the same pressure of the set Reducing Valve on the system
To re-charge an Expansion Vessel simply connect a pump to the schrader valve and inflate to the desired pressure. At this point additional leak tests can be made on the schrader valve and flange plate using a leak detection solution, if no leaks are found then re-test the pressure setting after 15-20 minutes to ensure the Expansion Vessel is holding its charge. If leaks are found at the Schrader valve or flange plate then replace the Expansion Vessel.
Reconnect the Expansion Vessel from the system allowing the system to re fill, at this point check for any system leaks.
Follow the useful links below for replacement Expansion Vessels and Products: