Can't repressurise expansion vessel

[Jaybee007]

Hi

I've got an expansion vessel which has lost its pre-charge. I've pushed the Schrader valve in and don't get any air out and also don't get any water so I assume the diaphragm is still in tact.

I've tried draining down the system to see if I could re-pressurise. I could hear water leaving the EV but even after the water stopped flowing from the hose I still couldn't re-pressure. When I use my foot pump the guage rose rapidly but as soon as I release the pump the pressure is released and none of the air has actually gone into the EV.

Does this mean the EV is knackered? I've changed the schrader valve but that made no difference.

Any suggestions gratefully received.

 

[simond]

If the diaphragm is intact, how do you think the air got out in the first place?

Wouldn't be a Vaillant boiler with a Zilmet EV by any chance?

 

[manortim]

I've had this before.

I would remove the Schrader valve core and try to recharge it then. Obviously it would hold but there will be nothing restricting the air entering the ev.

If that works, you need a new core.

If it doesn't......then the likely culprit is the hose from the ev to he system is blocked.

This us very common on oil boilers and certain gas boilers.


If clearing the blocked hose.....or if hose not blocked and Schrader core not at fault.....only thing can be is ev complete. Not a common issue.....

Usually when ev is shot....they're full of water.