Pluming makes a loude bang when switching on

[neilsumner]

We've recently moved into a new house, sometimes when the heating switches on there is an almighty bang from the pipes it sounds like someone has just whacked the pipes with a large hammer! I think it's loudest from the airing cupboard which contains the CH pump, 3port valve, timer and HW cylinder. It doesn't always happen though.

Any ideas what is causing this?

Cheers

Neil

 

[werewolf]

How long does the noise last? Do you get dhw and ch? Could be pump sticking. Need more info.

 

[lor]

bet you've got a honeywell 3 port valve and that is the cause of the banging .
(interesting way of spelling plumbing)

 

[neilsumner]

Thanks for your replies.
It's only one bang on first startup but it's difficult to pinpoint because it travels through all the pipes and sounds loud everywhere!
The CH and HW works fine it's a Potterton boiler by the way, about 20 years old but seems to work ok!

The valve has a blue plastic cover on it so looking on the net I think it is a Horstmann.

My fingers don't keep up with my brain half the time when I'm typing.

Cheers

-Neil

 

[gas4you]

Could be a BG drayton valve

 

[shakey1953]

Could be a BG drayton valve

my c/h did that so i drained all the water then let it fill up again then bled it while it was hot now no probs

 

[D_Hailsham]

bet you've got a honeywell 3 port valve and that is the cause of the banging.

Are you saying that only Honeywell 3-port valves have this problem? If so, what causes it?

 

[Agile]

Four year old thread!

 

[Whitespirit66]

Four year old thread!

Same as the TV. Repeats, repeats and more repeats.

 

[D_Hailsham]

Four year old thread!

Didn't see that.

Oh well.