Water heaters and expansion vessel

[joelpeyton]

Silly question coming up.

How does the expansion vessel work when connected to the cold water supply on a unvented water heater.

Surely it would need to be on the hot supply pipework to allow for the rise in temperature and so the expansion of the water?

Or am I just looking at it the wrong way.

 

[adlplumbing]

send a pic

 

[mysteryman]

The water expands back into the expansion vessel via the cold supply between it and the cylinder. That is why you must never fit any valves between them. The expansion vessel is on the cold so it doesn't have to handle hot water or act like a radiator and waste heat.