Vaillant Ecotec expansion vessel question - wont hold pressure but no water in chamber?

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Hi,

I'm 99% sure my vessel is knackered, but wanted to double check.

Vaillant Ecotec Plus 618. Probably 12 to 15 years old.

Symptoms are:
Boiler stops working due to low pressure
It increasingly needs topping up to get pressure back
This morning water was a fast trickle out of the external pipe

I've removed the casing. Checked the pressure on the schrader valve, and there was nothing there. No signs of water. I pumped some air in, to see if adding some pressure would cause a wet splutter, but it didnt.

So I knocked open the bleed valve of the upstairs towel rail (there was no pressure).
Then pumped away at the schradar valve. The pressure went up, but then dropped as lots of water came out of the towel rail.
I was hoping that water was being displaced from the EV, but I'm sure more water came out than could fit in the EV.
So I did up the towel rail bleed valve and pumped some more air into the EV, up to 1bar.
Refilled the system via the refill loop. Noticed that the pressure on the EV went up to 1.2bar.
Fired the heating on and went out for an hour. When I got back the heating was still on, but pressure in the EV very minimal as, as was pressure in rest of the system. I had put a bag over the external vent to see if any water would be lost when out and it didnt look like it had, but given the air that I had pumped into the system there is probably still a lot of air in the system that will be helping it manage the pressure.

A new vessel is £45 on amazon and looks easy to fit, but I dont want to get a new one then still fit / bleed it wrong.

Any advice please!
 
Last edited:
Perhaps obtain the services of a gas safe registered engineer? You should be testing after work on a gas appliance. It could be the vessel, could be the prv or both.
 
Perhaps suggest to your Gas Safe engineer that he / she replace the Schrader valve insert. Not expensive, can be bought from Halfords, but there are two sorts, short and long. Can be tested by inflating vessel, then putting a bubble of spit over the mouth of the valve - if it bubbles up, insert has failed.
 

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