Mysterious Banging noise

[mike2801.lee]

Hi all,

I live in a first floor maisonette property and have been experiencing a loud and unusual banging noise coming from below our bathroom, or at least that'where it sounds like it's coming from.

The layout of the flat below is exactly the same as ours, so our neighbour's bathroom is directly below our own. Our neighbours believe the noise is coming from our flat above, but we can't attribute it to anything on our end.

I've heard the noise from inside both flats and if sounds a lot louder down there, as if someone is taking a sledge hammer to their bathroom wall. That being said, I don't want to rule out that it's not us, and thought I'd register here and post a video I captured to see if anyone can suggest what might cause something like this.

We have no central heating in our flat. Instead, we have electric storage heaters. We have a water tank in the loft and an immersion heater in the airing cupboard to heat our water manually (no timer, just a power switch). We only heat the water when we need to do the washing up / have a bath.

There is no pattern to the banging except it always happens at night, typically 22:00 to 00:00. We have experienced the noise even when we haven't used hot water for days prior.

I'll be more than happy to answer any questions about our setup if it helps.

Link to the video I uploaded to YouTube is: https://youtu.be/m67W6yd312I

Many thanks in advance!

Kind Regards,

Mike.

 

[lame plumber]

water pressure build up over night, causes tank in attic to pass and fill, then the valve closes with a bang, waves cause it to open and close so bang bang bang. hang a yogurt pot on the float arm so it fills with water and helps stabilise the arm and stop the waves affecting it. the banging is water hammer in the pipework in most cases as sound travels really well in pipes OR you wc inlet valve is wearing and opening n closing in a similar manner with pressure build up at night if they are mains fed.

 

[Amjad]

ive come across a similar issue and in the end replaced a lead lock coming from the main pipe line connecting to the copper pipe...now I have no more noise - also thames water came and installed a mains isolating valve and im sure it contributed towards the pressure flow - all is well now - just seen the video and it sounds disturbing having that during the night - hope its sorted out?

 

[Radioman]

What happens if you turn on all the hot and cold taps when the knocking starts? Is it possible to isolate your cold supply either with the stopcock or water meter?

 

[mike2801.lee]

What happens if you turn on all the hot and cold taps when the knocking starts? Is it possible to isolate your cold supply either with the stopcock or water meter?

Turning on the taps has no effect and doesn't stop the banging. Yes we can isolate the cold water supply.

 

[mike2801.lee]

water pressure build up over night, causes tank in attic to pass and fill, then the valve closes with a bang, waves cause it to open and close so bang bang bang. hang a yogurt pot on the float arm so it fills with water and helps stabilise the arm and stop the waves affecting it. the banging is water hammer in the pipework in most cases as sound travels really well in pipes OR you wc inlet valve is wearing and opening n closing in a similar manner with pressure build up at night if they are mains fed.

I read up on water hammer but I've been up in the loft when the banging occurs and it's not as loud up there and there are no sounds of water flowing through the pipes either. I've also placed my hand against various pipes to feel for vibrations during the banging but can feel nothing!

 

[Radioman]

Turning on the taps has no effect and doesn't stop the banging. Yes we can isolate the cold water supply.

So if you isolate your cold water and turn on the hot and cold until they stop flowing thereby emptying the tank in loft does the banging stop? If so then the issue is in your flat. If not the issue is either in the mains water supply.

I have heard of a sump pump in a basement causing an issue like this. It was on a timer that fired it up at a set time if the float level was up high enough.

However to me that sounds like someone trying to break up a concrete slab rather than water hammer.
Are you in a semi detached property?

 

[mike2801.lee]

So if you isolate your cold water and turn on the hot and cold until they stop flowing thereby emptying the tank in loft does the banging stop? If so then the issue is in your flat. If not the issue is either in the mains water supply.

I have heard of a sump pump in a basement causing an issue like this. It was on a timer that fired it up at a set time if the float level was up high enough.

However to me that sounds like someone trying to break up a concrete slab rather than water hammer.
Are you in a semi detached property?

I've completely drained the system previously by running the taps and emptying the water tank but the banging isn't consistently happening. It can go days or weeks without incident and then start up again out of the blue with no change to our use / routine. If it was happening without fail every night you could use process of elimination to figure out what isn’t the root cause.

There's only so long we can go without running water to test!

It's a semi detached property but there is a room between the bathroom and our next door neighbours and the noise is definitely coming from the bathroom side as apposed to the neighbours side.

 

[Radioman]

Sorry I am stumped. If it does it with the mains off and no water flowing in both properties must be external. Or a poltergeist

 

[jacquiplumb]

I have had this before ended up being a heating pipe not notched properly in the properties.you say it happens of a evening ? And when its cold and of a evening. This is the time most people have there heating on. Could be the pipe has no room to expand or contract .i havent read all the threads so i could be wrong but thats what it seems to be to me