Buzzing Hot Water Tank

[KMB17]

My hot water tank has started emitting a horrible humming/buzzing noise, but it does it through the night (not heard it through the day yet) when both the hot water and heating are off.

It's in my son's bedroom so am a little worried that it could be leading to something dangerous. It's a gravity fed system - cold water tank is in attic, cylinder is in airing cupboard, but the cylinder is about 5 years old and powered by a newer boiler (which was fine about 18 months ago when it had a check up)

Does anybody know what could cause this, and what I can do about it?
Cheers

 

[Burnerman]

Does your copper cylinder have an immersion heater that you leave switched on?
John

 

[KMB17]

Sorry, going to sound really dumb: how can I find out? Not sure what I'm looking for...

 

[Burnerman]

The standard copper cylinder, covered in a coloured insulating foam?
The immersion heater is a cylindrical thing, usually with a black plastic cap, screwed into the top of the cylinder at a slight angle...it has an electric cable going into it which powers up the element of the immersion heater. Is that any clearer, or is yours a different type?
John

 

[KMB17]

Ahh, gotcha. Yep, we have one of those, and yes it is switched on. Just assumed it had to be. Is that what's making the noise?

 

[Burnerman]

It could be.....when the noise starts, turn the thing off and see if the noise stops. Normally you use the immersion heater for just boosting up the hot water supply, but there's nothing to stop you leaving it on continuously as its controlled by its own thermostat.
John

 

[KMB17]

I'll give it a try next time the noise starts.
If I therefore turn it off, I'll still get all my hot water etc, yeah? The thermostat on the side of the cylinder is only set to 35 anyway!

Sorry, I'm useless at this sorta thing. When would I possibly need to boost the system, or can I just leave it off all the time - if it is the cause anyway.

Thanks for all your help!!

 

[Burnerman]

Sure, the boiler should provide all the hot water you need - usually the strap on thermostat on the cylinder is set to 60 deg though. The immersion heater stat is in fact under the black plastic cover on the top.
John

 

[KMB17]

Right, me again.

It made that noise last night so I turned the immersion off, didn't make a difference unfortunately.

Any other ideas?

 

[Burnerman]

Hmmm. Right - when it happens again, just listen to the water tank up in the loft. If there's a little bit of valve flutter there could be some noise transmission down the pipes. Presumably you've felt the cylinder stat for any vibration? Not that it should be making any!
John

 

[KMB17]

Not sure how to explain it, but when the cylinder fires up I hear a...erm...its almost a metallic rattle, but not quite... Its as if two metals spoons are very gently rattling together. I've felt everything and nothing ever seems to be vibrating and the noise never goes away whilst hot water/heating is on, so I always assumed it was a noise coming from within one of the metal blocks - like the one for the immersion heater on the top of the cylinder, but I could never pinpoint where it was coming from.

Probably should have mentioned it sooner! It does that and has been for as long as we've been in the house. This buzzing/humming noise is relatively new, nothing is vibrating because I re-checked. I haven't looked in the loft, although my husband has been up there when heating has been on and never mentioned a noise. I'll double check it when the noise happens again.

Just strikes me as odd that it only does the humming noise when the heating/hot water is off, and only ever through the night, stopping again when the boiler fires up for the morning hot water.

Sigh, I'll keep investigating! Kelly

 

[Burnerman]

OK do you know if there are any motorised valves in or near the cupboard where the tank is? They either have two or three copper pipes going into them, with an aluminium box on top, with an electric cable going to them?
(Sorry, not bright enough to post pictures)
John

 

[KMB17]

Yes there is - no idea what its for though! The cable runs to a plastic...its like a light switch box only flatter and bigger and there's no switches on it.

Kelly

 

[Burnerman]

OK thats a motorised valve, and its connected to its wiring centre...all very jolly and correct there.
Basically this valve takes the hot water from the boiler and directs it for you - either into the hot cylinder for your bathing water or around the central heating pipes.
It could be this making a buzzing - feel it, but it could be hot if the heating is on. There is a small electric motor in there which turns the valve when its told to.When alls quiet, at night, sneak up on it and feel for any vibration.
You know the strapped on stat around the cylinder? If you turn the stat down then up, I think you'll hear a whirring from the valve.
John

 

[KMB17]

Haha, sneak up on it - I like that!

Will give it a try tonight. Heating is definately on at the minute as we have snow!

You said yesterday that most people have their cylinder therms on at around 60; am I causing any harm by having it on at 35? Thats what it was set at when I moved in and I've just never touched it.
Probably a really stupid question but figure I'm asking other stupid questions anyway!

Thank you so much for all your help with this! Kelly