Noisy Valve on Hot Water Cylinder

aliadds

I posted a similar question on the heating board but didn't get much response so I thought I'd try here instead.
My central heating system is 3 years old, and I've been having a problem with what I would describe as a howling noise when I switch the heating off! I've now traced the noise to a Drayton zone valve on the hot water cylinder. There's a small switch on the top which looks like it may be sticking.
Any advice on the nature of this problem, and whether its something I can deal with or need to call a plumber, would be gratefully received!

red40

Howling sound usually comes from the central heating pump and noise can travel through the pipework. Although it maybe the zone valve motor on its way out.

If you suspect its going to fail, which it usually does and its usually over the Christmas period :eek: I would be tempted to get a plumber out to have a look at it, before they all leave the country on their Christmas breaks.