Pressure vessel on cold water supply to boiler?

[Wiredcharlie]

A nice man from British Gas serviced my combi-boiler the other day and told me I needed a pressure vessel fitting on the water supply to my house.

He explained that when I turn off the hot tap, the hot boiler would cause the water to expand and thus increase the pressure in the cold water supply. He explained that this happens because there is a one way valve at the water meter and so expansion back down the supply pipe is not possible.

Now that's all very well, but why is this suddenly necessary after all these years. His remarks (and accompanying quote) were not motivated by the need to solve a problem. Nor had he put a pressure gauge on my cold water supply to see if the increase in water volume produced a significant increase in pressure in the volume of water in the length of pipe my side of the meter.

Please could someone fill in the blanks?

 

[ianniann]

This idea does exist but the vessels rarely seem to be used. At least one source says it is only necessary with plastic pipe since copper pipe can take the pressure. I don't know myself.

 

[dextrous]

Please could someone fill in the blanks?

blocks (a phonetic answer)

 

[muggles]

If you've had the boiler a while (presumably you've had it over a year if it's being serviced) and you've not suffered from blown pipes/joints I shouldn't worry about it

 

[Wiredcharlie]

Is anyone fitting pressure vessels on the cold supply when they fit combis, or is this just a British Gas thing?

 

[ianniann]

Is anyone fitting pressure vessels when they put a water meter onto a supply to an existing combi?!?

 

[twgas]

Didn't know BG were fitting them, I haven't done any.

 

[dextrous]

Didn't know BG were fitting them, I haven't done any.

Think an afternoon off "training" may be looming

 

[ChrisR]

Look here :
all the answers

//www.diynot.com/forums/viewtopic.php?t=220726

 

[twgas]

We were told, many months ago, that if the increase in pressure (we no vessel) causes water leaks then a mini vessel might be reqd, but combis are forever leaking anyway, even when there is no NRV on the main.