Fitting an Expansion Vessel

Standard Toaster

Novice here when it comes to plumbing but consider myself handy enough to DIY most jobs.

Moved into new place and so far I've replaced the boiler thermostat and circulating pump, both died a few days of using the heating.

So far so good. The external expansion vessel I notice is bleeding water from the schrader valve so that's failed too.

The pressure release valve also seems shot as it's leaking water when with the system cold.

I have a replacement vessel and valve ready to go (18ltr)

So I hope to DIY this one too. I figure I might get away without draining the system if it was just the vessel but with the failed PRV too I feel I'd need to drain.

There's no drain on any of the rads so also maybe a good time to fit one on the lowest one and add some inhibitor too while I'm at it. I'll prob add trvs later.

What's the process here for draining and filling/re-pressurizing the system?

I notice there's no filling loop like my old place.

I've yet to find the mains water supply and I expect it's that above in the hot press.

Any advice appreciated. My plumber guy can't get to me soon enough hence trying to DIY this one.

halkar

The one on the top looks like auto refill valve. It will top up the system if pressure goes down if its working. The other one looks like main water supply . I think it also feeds the tank in the attic.

10-10-20

There's not much else to say other than to close off a few rads and then drain off whatever comes out of the pipe at the expansion vessel. That's what I do - just have a few vessels and around 20l of bucket-space available - and let-rip. Don't forget that the 18l of expansion vessel is probably now full of water, so it's now around 25kgs in weight.

Lookup how to fill the expansion vessel as this probably needs to be done on a bench before it's mounted.

Then fill slowly and chase the air out through the rads.