Vibrating/loud banging from pipes when hot water taps are used

[silvaplumb]

Hi all,

Last autumn/winter whenever I used the kitchen or bathroom hot water taps the pipework would gently hum for a few seconds and then disappear. As the weather got warmer the problem went away. This also coincided with me turning the central heating off.

However, now that it's getting colder again, and the central heating has gone on, the problem is back..but far worse than before.

Now whenever I use the hot taps the pipes start to bang and it sounds like someone is taking a pneumatic drill to the wall! This lasts anywhere between 5 and 30 seconds and occurs only when water is running from the taps. If the taps are off, there is no noise.

The noise appears to be coming from the wall where I know the cold water feed pipe from the mains heads up to the hot water storage tank, but is also the same wall where the hot water pipes from hot water tank supplying the bathroom and kitchen (gravity fed) head down - so doesn't help in identifying which set are to blame!

I'm not sure if the central heating is playing any part in this but it seems odd that during the summer when it was off i didn't hear a thing from the pipes - despite still having the hot water on and using hot water taps as normal. The boiler is a conventional one.

Any ideas as to the cause of this (and more importantly a solution!) would be most welcome.

Thanks

 

[Hardy1]

it is probably water hammer, has this ever happened before?, or is this the first time its ever happened this year?

 

[mikeygas]

Also worth checking out the ballcock in the cold water storage tank in your loft (the big tank). If this is shot it will send vibration's back down the rising cold water main (i.e water hammer).

 

[silvaplumb]

Hardy1 - used to get this last winter but not as banging was nowhere near as severe and was sporadic. Now it occurs whenever a hot tap is turned on, so 2/3 times a day!

MikeyGas - what exactly am I checking with regards to the ballcock? If it is shot, will it be immediately obvious to me?

Thanks guys!

 

[WHPES]

First try changing the float valve in the cistern. Then go round and put extra pipe brackets all over the place on the pipework. If there is exposed pipe, set the pipes humming and go round placing your hand on different sections of pipe until you feel it. Basically what's happening is one section of pipe somewhere is resonating like a guitar string. Sometimes rags stuffed behind pipe can dampen the vibrations.

 

[Nat]

Also worth checking out the ballcock in the cold water storage tank in your loft (the big tank). If this is shot it will send vibration's back down the rising cold water main (i.e water hammer).

I'm with mikeygas. Could be the washer in the ballcock though this doesn't explain the sporadic nature of the occurrences. It's a relatively easy job to change the washer so might be worth a go. As you draw off hot water the ballcock is what refills the big cistern in the loft.

 

[WHPES]

The float valve (ballcock) is only setting the vibration off. It's the pipework you need to look at as well. For those who did physics for A level, it's all about harmonics - You get an oscillation in pressure at a natural frequency of a length of pipe and it starts resonating at its set pitch, just like the strings on a musical instrument.

 

[Guest123]

Might be your taps. Are they modern ceramic disc taps? As taps wear, the seating can cause the jumper to osicilate and in some cases can either switch the water off too quickly causing water hammer or cause vibrations through the pipe. Heat from the hot water system can enhance this.

 

[silvaplumb]

This evening I closed the valve from the mains feed in a bid to reduce the pressure of the water heading up to the storage tank and it seemed to bring some success. The pipes still vibrated when the hot water tap was opened but it wasn't as violent as before, this time it was more of distant rumble than the usual jackhammer! And later in the evening when running a bath I didn't hear anything at all..will update on what tomorrow brings.

 

[silvaplumb]

This evening I closed the valve from the mains feed in a bid to reduce the pressure of the water heading up to the storage tank and it seemed to bring some success. The pipes still vibrated when the hot water tap was opened but it wasn't as violent as before, this time it was more of distant rumble than the usual jackhammer! And later in the evening when running a bath I didn't hear anything at all..will update on what tomorrow brings.

The banging was back with a vengeance this morning..