Loud banging in pipe when water is off?

[zenonithus]

Hi all,

I had a stop lever valve fitted in my kitchen to isolate the water in the flat. The mains water comes from an old iron pipe running down the wall that is also running to the flat below so essentially sharing the main water pipe. It tapers off under the floor and connected to copper pipes where my kitchen sink is. This is where I had the lever valve fitted.

About three weeks ago I started getting really loud banging noises from the main iron pipe area just randomly in the evening. Ever since then I sometimes get banging noises in the morning or evening or at night. It sounds like it comes from the main pipe and stops at the stop lever valve.

When I turn the stop lever valve off the banging stops, so I can't help but think it is something to do with this?

Any ideas as to what it can be. I do get water hammer when I turn the taps off, though this has been happening since I moved in. This hammer issue when the water is off is recent.

 

[zenonithus]

Its strange as I just went to check and the banging has suddenly stopped even though my stop lever is on?! Though I will expect it to start up again in the morning or at night. Is it possible it occurs when the flat below run their water? If so how comes it stops when I turn off my stop lever valve?

 

[Madrab]

Banging is usually to do with water hammer. That can be a toilet valve, water cistern valve, washing/dishwasher valve sending shock waves down the pipe when it closes, it can also be down to loose pipework. It could originate in either your own or the neighbours pipework if it's shared.

 

[zenonithus]

Hi Madrab, One thing I did do when it kinda started was loosen the plaster holding the main iron pipe we share so it is pretty much free standing. The plaster was pushed in at the sides fixing it to the wall making it more stable, though I took it all out as renovating the kitchen so this could be making the pipe shake and wobble as you said loose pipework. Is it just that the pipe is now not properly fixed to the wall and loose and needs fixing to the wall? Could any damage have been done to the pipework as a result of this?

 

[Madrab]

When it hammers, hold the pipe, does it stop? If so therein lies your issue and the solution

 

[zenonithus]

Unfortunately it made no difference I had to really lower my lever valve to almost off to dampen down the sound and have very low water pressure as a result now. It almost sounds like the high water pressure is hitting the valve when I touch the pipe below the lever valve I can really feel the "ssshunk!" sound vibrate, touching the pipes beyong the lever valve and it's not as strong. Is it possible it has something to do with my lever valve and the high water pressure going through it? here is a picture of the pipes in my kitchen. The large iron mains supply pipe is to the left on the wall and it runs under the floor, connecting to the copper with the newly installed lever valve.

 

[Madrab]

All you can do really is try a new valve and see if it sorts it. Could be a sympathetic vibration off of the ball valve, though holding the lever usually stops/changes that, so it's then obvious it's a faulty valve. If it sorts it though take the other one back.

 

[zenonithus]

Yeah it could be that, though the valve was brand new and the banging noises were not present when it was installed, they have come on only recently. I did notice at the time I noticed them my water pressure was all over the place. When I turned the tap on in the bathroom relatively low the pressure would be shooting out. The tap was very sensitive and I couldn't get low pressure out of it at one point. Also everything like the bath, sink, toilet all make hammer noises when turned off. Wondering if I need to install a device to relieve the hammer pressure?

 

[Madrab]

I wouldn't say that introducing a full bore stop valve would cause the symptoms you're are describing. If it's all started ever since you cut the wall away from the pipe then it has to be someting to do with that, unless that is just coincidental. That as well as your pic shows that none of the pipework is supported.

That being said if you are getting pressure/flow fluctuations then there could be an issue from your neighbour or the mians if it is shared. Unfortunately it's a difficult one to diagnose without being onsite.

 

[zenonithus]

madrab, the pipe on the wall is still fairly secure to the wall. I even held it firmly to the wall and the hammer noise still came through.

I turned the water pressure down and it has dampened the banging. Its still there but very faint, enough to give me ok pressure and not damage my pipes with heavy hammering.

I also had a look at the flat downstairs. I realised the banging is due to their kitchen cold tap shutting off and also when their shower shuts off. The constant banging is from when their newly installed washing machine is running. Also when the washing machine drains at the end it also hammers.

We did a test and the hammer does not happen if I shut my water off at the lever valve. So all the noises are happening at my end though due to operating the water below. Could the washing machine increased the water pressure somehow?

 

[Madrab]

Could the washing machine increased the water pressure somehow

No, well yes kind of, the washing machine has a solenoid valve in it, when that shuts abruptly it can send a hydraulic shockwave back up the pipework that causes a banging in the pipes especially if any are loose and that can resonate back up to yours.

One solution could be a Washing Machine valve (WMV) with a built in check valve or fit a shock arrestor that sits in between the WMV and the pipe. You could also try an arrestor before your cold mains to try and remove any other outlet that may be causing it.

 

[zenonithus]

Cheers Madrab. The washing machine is the flat below so would need to think of installing something at my end. Someone also suggested that it could be air trapped in the faucet pipe that is closed off coming direct from the mains and that there could be air trapped in there that cant escape. Otherwise the shock arrestor sounds like the best option. Where would be the best place to fit it? Before or after the lever valve in the picture?

 

[Madrab]

After would be the easiest but it may be a trial and error.

Air trapped at the end of a pipe would actually act as a shock arrestor, as that's basically what an arrestor is, trapped air and some have an added piston. You can make your own with a piece of pipe and a soldered cap end.

 

[John D v2.0]

Agreed with madrab that it's a shock wave caused by the moving column of water being stopped abruptly. Ideally the arrestor would be fitted as close as possible to the appliance so it is"in front" of the whole column of water and can protect all the pipework, but if it's only bothering you you only need to protect your own. Fit it as early as you can in your pipe work, as long as it's before any tees or bends it should absorb any pressure waves before they bang your pipes.

 

[zenonithus]

cheers guys. So where in the image would you think is best?