Hot water foghorn noise

[fsa259]

For the past few months, turning on the hot water produces a certain noise. Sometimes it's a low pitched droning hum, at others it's an almighty foghorn and sometimes nothing. It's really hard to pinpoint exactly where it's coming from as it feels like it's from all directions. It isn't a tapping noise, as described by some on some threads...a constant hum. The noise goes away by itself after max 30 secs of running the hot water. Turning on the cold water at the same time reduces or eliminates the sound. Turning off the hot water gets rid of the sound immediately. It happens with all the hot water taps.

Based on threads I've read here and other sites, it's either down to the ball-cock mechanism in the filler tank in the loft or air in the system. Are there any other 'tests' I could do to narrow it down? Are there any other causes I'm over-looking? Is removing the air in the system the same as bleeding the radiators?

Please let me know if there's more information you need to get a better idea.

On a related note, how does it make such a loud noise? At its loudest, it feels like the walls will cave in. Is it just resonance?

Thanks in advance!

 

[oz-plumber]

Do you have mixer taps or taps with washers?

If you have taps with washers, it could be the washers.

Does the noise stop when you open the taps more?

 

[oz-plumber]

Do you have mixer taps or taps with washers?

If you have taps with washers, it could be the washers.

Does the noise stop when you open the taps more?

 

[fsa259]

They are't mixer taps, individual hot and cold. I presume they have washers as they are quite old. The noise doesn't stop when opening the taps more...sometimes it gets louder. I ruled out tap washers as it happens on all 3 hot water taps in the house (unless all the washers conspired against me).

 

[Darren Jackson]

Turn the cold mains off or tie up the float on the ball cock and then run the hot taps if the noise stops it's a good indication the ball cock is the culprit.

 

[townfanjon]

^^^ I was just thinking the same as Darren, possible CWSC ball valve .

 

[fsa259]

Turn the cold mains off or tie up the float on the ball cock and then run the hot taps if the noise stops it's a good indication the ball cock is the culprit.

It's a real mission getting into the loft, so I will try the cold mains off route (by which you mean the main stop valve by the water meter?)

I will try this out a few times, since the noise doesn't always happen, and report back.

Thanks for the tip.

 

[joni os]

The water in radiators is totally separate from hot water to taps. Bleeding radiators as mentioned in OP will have no effect. Bite the bullet, get into loft. That's where your solution will be.

 

[fsa259]

The water in radiators is totally separate from hot water to taps. Bleeding radiators as mentioned in OP will have no effect. Bite the bullet, get into loft. That's where your solution will be.

I now realise that was a stupid thing to say. I only made the association as it seemed like the noise was loudest form the radiator side of the room.


I turned off the cold water mains and ran the hot water till empty: no noise. Although, when I then turned the cold water mains back on, all I could hear was the HWST gradually fill. If the foghorn noise was because of the CWSC ball valve, shouldn't it have come back as the HWST filled from the CWSC after having been emptied?

More importantly, since that I can't seem to get the foghorn noise to come back, so now I really don't know what the issue was.

 

[fsa259]

The water in radiators is totally separate from hot water to taps. Bleeding radiators as mentioned in OP will have no effect. Bite the bullet, get into loft. That's where your solution will be.

I now realise that was a stupid thing to say. I only made the association as it seemed like the noise was loudest form the radiator side of the room.


I turned off the cold water mains and ran the hot water till empty: no noise. Although, when I then turned the cold water mains back on, all I could hear was the HWST gradually fill. If the foghorn noise was because of the CWSC ball valve, shouldn't it have come back as the HWST filled from the CWSC after having been emptied?

More importantly, since that I can't seem to get the foghorn noise to come back, so now I really don't know what the issue was.

 

[Best]

Your hot water cylinder wouldn't have emptied. Just the cold tank would have drained.
The hot tank always stays full of water to the top, even when the supply is off.
The noise is probably the ball valve in the cold tank and it can be intermittent and also only make the noise when ball valve slightly open.