Pipes rattling - water hammer?

pledgeX

I moved house a few months ago and since moving in have had issues with pipes banging/rattling.

I've tried investigating the problem to see when the noise occurs. By far the worst noise comes when I drain a full sink full of hot water from the upstairs basin.

I read up on water hammer but I don't think this is the issue here as from what I've read water hammer is caused when a tap is turned on or off quickly so the water 'bounces' in a sort of shockwave effect. Obviously this is not the case in my example above as the noise doesn't come when I turn my tap off, only when I remove the plug.

I've heard banging from the other taps in the house (one in the bath in the same room as the basin, the other tap is in the kitchen), but it's not as bad as the basin. However, I don't think it's entirely due to drainage as if I put the plug in and run the tap, I can hear some banging, but it's nowhere near as loud or as frequent and is usually only audible if you're really paying attention.

Something that seemed odd to me was the fact that hot water seems to make more noise than cold water. I thought about the hot water coming into contact with the cold pipes may cause expansion/contraction, but the noise just seems too loud for that.

One last piece of info; the banging doesn't stop immediately. It slows down immediatley, but sometimes I can still hear a bang say once every 15 seconds for several minutes after I finished running the tap/draining.

Oh, and we have a gas combi boiler (it's one of the Worcester Bosch Greenstar Junior series if that makes a difference - around 2-3 years old). There is a cold water storage tank in the loft but has no water in and is no longer in use.

Anyone know what my problem could be here? Any idea how to fix it? I'm worried that it is doing some damage to the pipework and one day we're going to get a serious leak.

Thanks.

ariba10

Try turning the main stopcock down until it is only open about half a turn, and then report back with the result.

ormus

if youre draining waste water and getting some banging, then check the waste pipe/s for proper fixing.
sounds like theres no pipe clips installed. the pipe/s should be secure.

bridgend_girl

Reading this I realised i have the water hammer problem. When the downstairs loo is flushed the pipes bang and crash terribly for up to 4 minutes afterwards. Being a bit of an ostrich I took a friends advice and have now turned the stock !!!! half ways closed-problem fixed but have to turn it up temporarily each time I want to run a bath or take a shower! LOL. How can i fix it properly? Any suggestions for a not very DIY skilled mum would be appreciated. Thanks.

DavidFx

This is most likely due to the expansion of the waste pipe when hot water passes through. The knocking is where the pipe is not free to expand (ie where it passes through a wall) and it moves in a series of jumps rather than a smooth continuous movement. Try spraying some silicon spray or furniture polish on the pipe near any pipe brackets and where the pipe passes through a wall or partition. A few applications may be necessary. The reason why the noise may go on for a while is that the same process occurs as the pipe cools down (contraction) and this takes much longer.

ariba10

To elaborate on my first reply. It is known as Water Hammer. Check this site.

http://en.wikipedia.org/wiki/Water_hammer

Chunks

Per the original post, think ormus and DavidFx are on the right track. Water hammer occurs on the filing side of things rather than the waste. Unsecured waste piping flapping about possibly coupled with noises re expansion and contraction 'friction' are where I would start looking.

pledgeX

DavidFx wrote: »

This is most likely due to the expansion of the waste pipe when hot water passes through.

It's a pretty severe expansion to make that much noise though surely? The other thing that makes me think this is not the case is that it still happened on hot summers days where the difference in temperature between the water and the pipe wouldn't have been hugely different. And I'm pretty sure if I run hot water in the pipe for a few mins to heat it up, put the plug in, fill the basin up, remove the plug, I'll still get the rattling, even though the pipe will already be 'warmend up'.

And I can't really get at the pipe apart from the section that runs from the plug to floor in the bathroom. It then goes under the floor and then into the wall that seperates the bedroom and bathroom and runs to the ground within this wall. So getting to the pipe would mean ripping up tile flooring and pulling down half a wall!

ariba10 wrote: »

To elaborate on my first reply. It is known as Water Hammer. Check this site.

http://en.wikipedia.org/wiki/Water_hammer

From the first paragraph of your link:
Water hammer is a pressure surge or wave resulting when a fluid in motion is forced to stop or change direction suddenly.

Surely this isn't the case In what I described as water is not in motion when it is forced to stop/change direction. In fact its the compete opposite!

Chunks

bridgend_girl wrote: »

Any suggestions for a not very DIY skilled mum would be appreciated. Thanks.

MSE experts will be along in due course but have a look at this link:

http://www.simplifydiy.com/plumbing-and-heating/mains-water-systems/water-hammer

Key is to find out where the 'hammer' is located (not the one in your tool box...) and applying a fix - adding pipe clips might be all that's needed.

martinthebandit

To be honest it doesn't sound like its water hammer to me, from what you have described it sounds far more like air is trapped somewhere in your waste system.

If it only happens from one particular sink I would be looking at the waste pipe route from that sink and seeing if I could eliminate anywhere that may be causing air to bubble up back against the water going down by seeing if I could secure, or reroute, it better.

I seriously doubt that there would be enough pressure in a sink waste to cause water hammer.

ariba10

Have you tried turning the stopcock until it is only open half a turn as I suggested earlier?

(Humour me please)