Expansion vessels / air in the system, a fair trade off?

[Polly1]

It occured to me last week that an expansion vessel is simply a container of air allowing physical expansion of hot water in a sealed CH system. My faulty expansion vessel (now seems to be OK after I charged it with a bike pump) resulted in water leaking out of my system when the pressure was as low as 1.4 bar.

So what I believe I have realised and hope you people will confirm, is that if I had just let a little air into one of the radiators, that the system would have expanded there & stopped letting water out.

This leads me to believe that I'm better off not letting every bit of air out of my system, which is what I've been doing every October, so the system has room to expand.

What do you reckon?

 

[ChrisR]

You're suggesting that you increase the volume of air in the system so that the pressure increase in heating isn't enough to make your rotten plumbing leak?

Air in the rads etc will stop them working!
3bar shouldn't cause any leaks.
Just do it properly!

 

[Polly1]

Yes I changed the 5 year old pressure release valve when I saw it letting water out at 1.4 bar, but the brand new one was letting water out at 1.7 bar which isn't what it's rated to.

It seems to me that there is a difference between a pressure build up and physical expansion of the water. If the pressure release valves were really capable of holding anything until 3 bar, that new one wouldn't have let anything out. It seems if there is no air whatsover in the system, that rating is reduced because the physical expansion just has nowehere to go, but out the PRV.

Now that the expansion vessel has been charged with air, no water is leaking out.

But as I said, it seems to me that had I not been so keen to release air from the radiators, my problem might have been very minor to start with anyway.

I don't agree with you that air in a rad stops it working, it just reduces it's output depending on the amount of air in the rad.

And for the amounts that plumbers charge to fix things, I am much better off trying to understand the problem(s) & understanding the alternative solutions.

For this job, my plumber wanted £350 to remove the boiler & change the expansion vessel. A full days work.

Instead, thanks to this forum, a bike pump seems to have done it for now. A little Air in the rads might have prevented the attempt to get £350 off me to start with.

He didn't tell me about generic expansion vessels either, you people did. Thanks for that as well.

 

[nuttynoonoohaha]

is your system still working Polly? If so how do you go about letting air into a rad, have only ever tried letting air out!

Cheers

It occured to me last week that an expansion vessel is simply a container of air allowing physical expansion of hot water in a sealed CH system. My faulty expansion vessel (now seems to be OK after I charged it with a bike pump) resulted in water leaking out of my system when the pressure was as low as 1.4 bar.

So what I believe I have realised and hope you people will confirm, is that if I had just let a little air into one of the radiators, that the system would have expanded there & stopped letting water out.

This leads me to believe that I'm better off not letting every bit of air out of my system, which is what I've been doing every October, so the system has room to expand.

What do you reckon?