Safe to pressurize expansion vessel on unvented system myself?

[Tanker01]

Hi All,

I have an unvented water tank that makes the vibrating sound when taps are turned on which I read is potentially down to the white expansion vessel pressure being off?

There is no gauge on that one to see if it is at the recommended 3bar. I believe the valve to be under the black cover on the top which is mounted above the system, vertically.

I see posts about safety on unvented systems so is it acceptable if I was to connect a track pump to the vessel and seek to charge it to 3bar?

Can I do it without draining the system?

Should it be done at a specific time, say after the hot water cycle has been on?

Thanks

 

[phatboy]

I've done one myself - turned off the supply to the cylinder, and then ran the hot taps until the water stopped. Then could recharge the expansion vessel. It was hard work though pumping it up. Check the valve is nice and tight afterwards, in case it wasn't before and hence the loss of air pressure.

 

[Agile]

Very strictly any work at all on an unvented cylinder should only be done by someone with the appropriate qualification.

However, recharging the air is probably a pretty low risk job.

If you did decide to try it then it must be done with the cold feed to the tank closed and a hot tap open to reduce the pressure to zero.

It is often difficult to achieve 3 bar pressure from a car foot pump operated by hand.

An unvented cylinder should be professionally serviced every year! An exploding cylinder can demolish a house! A professional should have insurance, Phatboy probably does not!

Tony

 

[Tanker01]

I called a plumber anyway and he suggested it wasn't the expansion vessel but instead the cold water valve that enters the cylinder, I've arranged for him to call down next week to try and diagnose it properly so I don't mess it up. Cheers for the replies.

 

[ianmcd]

you have done the best thing, as already suggested the unit should be serviced every year anyway so will not do any harm to have a professional look at it