Can anyone tell me what this is??

[DIYNewbie1]

Looking at having a boiler installed and looked at a family members recent install where all the work looked really neat and tidy. I spotted this (see pic) and asked what it was. The answer was nobody knows except it is required if you have a combi and a water meter. Anyone help me out as to what it is and is it an essential piece of kit.

Untitled

• DIYNewbie1
• 2 Apr 2010
• 1

 

[heatingman]

it a small mains expansion vessel, often used to stop water hammer.

 

[picasso]

In this case its fitted because the water meter has a check valve that stops the hot water expanding down the mains.

 

[DIYNewbie1]

Thanks! Is it a definite requirement for a combi boiler with a water meter or have i been misinformed?

I was trying to show the image in the post but doesnt work i need to sort my settings out

 

[ChrisR]

The reason you need it is that with a water meter you will probably have a non return valve in the supply. That means the water in the combi may have nowhere to go when it expands on heating.
It usually just pushes past the float valve in a WC cistern, but some have hysteresis so it can't.

 

[twgas]

Its a mini expasion vessel, takes up the expansion of the water in the boiler when the taps are off, it also can prevent water hammer.

 

[ChrisR]

You know what, it's an expansion vessel!!!
Shall we get some more people to tell you ?

 

[dextrous]

So what is it? And what's it for?

 

[glasgowgas]

So what is it? ITS AN EXPANSION VESSEL And what's it for?ITS WHERE THE EXPANDED WATER GOES

 

[dextrous]

So its a vessel to let expanded water, er, expand into

What happens if there's more expanded water than can be held in the aforementioned vessel

 

[JonB]

I have a Combi & a water meter, But havn't got one of those. All seems to work OK.

 

[Servotech]

It's the first one I've ever seen too and I fit lots of combs.
I don't think that they are nessesary.

 

[kevindgas]

It's the first one I've ever seen too and I fit lots of combs.
I don't think that they are nessesary.

on some boilers they are required, on most they are not, never a bad move to fit one though.
it will also stop shuddering in loose tap spindles (the type with a 2 part shaft/washer post)

 

[glasgowgas]

So its a vessel to let expanded water, er, expand into

What happens if there's more expanded water than can be held in the aforementioned vessel

it will build up to such a dramatic pressure that when it blows up, it will, quite litterally take us into another dimension, one where dogs and cats are friends, and where RE teachers stop asking questions they already know the answers to

 

[dextrous]

it will build up to such a dramatic pressure that when it blows up, it will, quite litterally take us into another dimension, one where dogs and cats are friends, and where RE teachers stop asking questions they already know the answers to

That'll be my wife then I "do" rithmetic