Noisy water pipes - Thumping noise with no water running

[P Stubbs]

I live on the first floor of a 3 storey apartment building and think I have an issue with my water pipes.

When I am running water from the taps or flushing the toilet there is no noise coming from them. However once I have shut them off I get a repetitive thumping noise about 5-10 minutes afterwards which lasts around 30 seconds.

At first I thought it might be water hammer and so after looking on Google I ended up turning my stopcock off, draining the system and refilling the water tanks. However this has had no effect. I have also tried turning down the thermostat on the hot water tank slightly but again this has done nothing. The pipes making this noise are in my kitchen under the floor.

I live in quite a hard water area so was wondering could limescale or sediment build up either in the tanks or pipes be causing this?

This past summer I had some issues with the overflow ball valves in both the hot and cold water tanks and ended up having them replaced. Is there any possibility that this could be causing the noise?

The only other thing I could think of is that perhaps it's a similar issue with the flat directly below and the noise is actually coming from them as there are times when this thumping does happen in the night when I am asleep and the taps have been off for hours?

I don't think it's down to loose pipes and almost certainly not due to high water pressure given I live in a block of flats. The building is around 30 years old and from what I can tell each flat's water pipes run at floor level both into and around each flat.

Sorry for such a long post but is this a simple fix or am I going to need to get someone out to take a look at it?

Thanks

 

[Riley]

Most likely a ball valve. Turn off your stopcock and use toilet and basin and see if noise is still there

 

[P Stubbs]

Thanks, I'll give that a try when I get in later. As my basin has a mixer tap does it matter if I run it hot, cold or something in between?

 

[Riley]

Basically what you are aiming to do is prevent the tank in the loft from refilling so it’s anythibg that will drain some water out of the tank

 

[P Stubbs]

No worries, I'll try that and see what happens.

 

[P Stubbs]

Following the advice I turned off the stopcock and flushed the toilet, in the following 15 minutes there was no noise.

So I then ran the hot water in one sink for around a minute and again in the following 15 minutes there was no noise.

Next I ran the hot water in a different sink again for around a minute and there was also no noise in the 15 minutes that followed this.

Finally I left it an hour or so and then turned the stopcock back on. Around an hour after this the thumping noise returned although I'd run no water and not had to flush the toilet since turning the stopcock back on.

Is that what you'd expect if it was an issue with the ball valve and is it simply a case that excess water is going from the tank and causing the noise in the pipes?

 

[Riley]

The noise will be the ball valve refilling the tank in the loft. Repair or replace

 

[P Stubbs]

OK I'm still slightly confused though. The noise is coming is from the pipes in the floor under my kitchen but my tank is in a high level cupboard between the kitchen and the bathroom and isn't making any noise except for when it's refilling with water? I don't have a loft as I live in a flat.

 

[Riley]

Ok well it’ll be the ball valve either way. It’s just vibration being sent down the pipe

 

[P Stubbs]

Thanks, I've had a look around and have seen an equilibrium ball valve mentioned as a potential solution to this. Does this sound about right and it is it a particularly difficult or time consuming job to install one in place of my existing ball valve?

 

[Riley]

I would just be fitting a brass part 2 valve

 

[P Stubbs]

Ok thanks.

I'll get a plumber booked in and see if they recommend either of the two options here.