Water Hammer - Flats

[JTBytes]

I live in a block of flats (it consists of a row of ground floor 2 storey properties, and a row of 1 storey maisonettes on top), I live in one of the maisonettes. There's a water mains which runs along the ground floor, and it splits off at various points to feed a number of flats.

I moved into my flat last summer. Come this spring a water hammer started one day. The sound is under my kitchen sink (the closest end point from my part of the shared mains). I've been able to work out it's not caused by anything in my flat (when I shut my supply off, the sound moves to where the isolation valve is). It can either be a single knock sound or a series for about 5-10 mins, but follows a typical pattern: weekdays it’s early morning until around 9/10 then 4/5 until as late as midnight, and weekends it can be through the day or none at all. This to me makes me think it’s likely caused by a tap or boiler rather than a loose pipe or dodgy cistern.

I've been able to get the other neighbours on my part of the shared mains to run their taps and nothing seems to trigger it. I suspect that it's coming from one of the ground floor properties before mine, as I’m near the far end of the block near the end of the supply.

Does this make sense to anyone and seem likely, or do you think I'm completely clutching at straws here?

Here's a link to the sound:

https://screenapp.io/app/v/xG2LCb2Cxx

And a rough outline of the property/supply setup.

 

[blup]

The times it occurs suggest periods of high use by all flats. So the change in water pressure caused by all the taps being turned on and off causes the pipes to vibrate. It’s made worse because the water pressure is high in order to supply the taps etc in the flats. It could be a design issue ( is it a long standing issue?) or as a result an increase in water consuming white goods/boilers - more taps and valves to interrupt flow.

 

[JTBytes]

It hasn't been reported as an issue prior to moving in (not to say that it doesn't mean it wasn't the case) however, I didn't have this issue for the first 6 months here. In terms of the amount it happens, it's not constantly throughout these time periods. For example in the morning it can be a single sound a few times and that's it. Likewise in the evening it can be several intermittent single sounds, followed by nothing until a series of several sounds for a few minutes much later. I understand your point, however, there can be long periods of silence during let's say peak hours. And days where it doesn't happen at all, and yet the block isn't empty, just single properties absent. This is why my thinking is focussed on a single property causing this. The odd thing is why it's affecting me given the shared mains I'm on, isn't the last off the mains, there is one more. There is a stopcock along the mains for each shared which splits off. Can they affect the pressure at all?

 

[blup]

I’d look at the last property on the mains because the water hammer goes back up stream and you are the first in line

 

[JTBytes]

Thank you. I'd just assumed it would be caused by a property before me, with the pressure traveling down along the mains. So I'm second from end (on the left), there's a group of four properties I'm shared with (all tested taps, nothing), then the last shared feed for the very end are two properties I believe. The odd thing is, we tested one of them, and nothing. The other is basically occupied all the time, it doesn't fit the pattern, but it's worth a try!

 

[Madrab]

Well, there's certainly a little knock but It certainly isn't bad as far as hammer is concerned. It also sounds remote, therefore all you are hearing is the travelled sound. Stopcocks wouldn't usually create hammer but can be the cause of the sound . Hammer is caused by pressure spikes in the system, usually created by valves that close too quickly acting against water pressure in the pipe. That then creates a pressure wave that will travel along the pipe and when that wave hits something that is loose - a pipe knocking against something or a jumper in a valve - it can create a knock.

I think what that may be is a valve shutting off quickly, like a WM/DW solenoid or a ceramic valve. I would be asking if anyone had a new appliance or taps installed around the same time. Trouble is that it could be created anywhere on the system but given it's a shared riser and I would expect other owners to be hearing it too.

 

[JTBytes]

Thank you for your insight, I really appreciate it.

The sound originates under my sink. I think the recording makes it sound more remote. It’s from where my mains meets my taps, it’s a straight line. The sound moves to where my stop cock is if I close it off. I’ve run every test I can think of and can’t trigger it, and it occurs when nothing is in use.

My downstairs neighbour can hear it but from my flat. It appears this isn’t directly affecting anyone else which is the odd thing, I don’t know why it’s targeted me.

Based on reading posts on here and other places I was wondering if it could be a tap or boiler. My management company has said no one has reported of having works done despite the fact I remember at least two (possibly three) properties having work at the start of the year. That said they’ve all run their taps and nothing (although they all did it differently, one for example ran everything the same time but I’m hoping to retest them next week).

The reason I mentioned the stop cock on the mains outside is that it has been used several times since I moved in and I’ve been told it’s not in the best condition. But again, I’m I feel like I’m clutching.

 

[Madrab]

The reason I mentioned the stop cock on the mains outside is that it has been used several times since I moved in and I’ve been told it’s not in the best condition. But again, I’m I feel like I’m clutching.

If the jumper is loose in the tap then yes that can knock if something on the system is created a pressure spike.

I don’t know why it’s targeted me.

It isn't targeting you per sé, all it really means is that there is something that's unique to your system that is creating the sound, though not necessarily what is actually causing the pressure spike. Does it change at all if you wind the stop tap to your property down, say half way? Hard one to catch though if it cant be re-created.

 

[JTBytes]

That’s good to know about the tap, thank you.

I’ve not tried closing my stop cock halfway, I’ll give it a go!

 

[JTBytes]

I tried it but unfortunately it didn't make a difference.

 

[blup]

Listening to your recording, it could be a loose pipe. The lack of consistency might be down to the change in water pressure due in turn to variations in water use by other flats. But, if feasible, I would try to isolate the flat upstream of you as a control measure.
Edit: upstream should read downstream

 

[dilalio]

You could try a shock arrestor.
Might not solve it but worth a try.

 

[JTBytes]

Listening to your recording, it could be a loose pipe. The lack of consistency might be down to the change in water pressure due in turn to variations in water use by other flats. But, if feasible, I would try to isolate the flat upstream of you as a control measure.

Hmm, that would be tricky, at least for myself to do. At the moment the management company is giving me grief which isn't helping. Thank you for your suggestion though.

You could try a shock arrestor.
Might not solve it but worth a try.

I'd considered asking a plumber to fit one but I had read they usually aren't effective unless placed next to the source, plus the cost of doing it. I assume it's literally a case of who knows if it will work?

 

[blup]

Hmm, that would be tricky, at least for myself to do. At the moment the management company is giving me grief which isn't helping. Thank you for your suggestion though.

I meant as a temporary measure to exclude possible causes. I appreciate there are practical difficulties in persuading someone to isolate their supply even if they are only on holiday for a week.

 

[Harry Bloomfield]

Log the dates, and times, when it happens, then see if you can match the lack of hammer, to when people are away on holiday. If your flat is the only one suffering the noise, then the likelihood is, that you have a pipe which is not properly fixed.