This house, 30 years old, has two water feeds, one for a drinking water
tap and one that drives through a water softener, in the garage, into
the house indirect system. Twice this year the house has been shaken by
drumming - sounds, and feels, like a helicopter just overhead! I've
managed to stop it by opening the drinking water tap for about 10
seconds. What's causing it and what's the remedy?

TIA

PA

Peter Able wrote:

Twice this year the house has been shaken by drumming - sounds, and
feels, like a helicopter just overhead!Â* I've managed to stop it by
opening the drinking water tap for about 10 seconds. What's causing it
and what's the remedy?

Water hammer, can be started by a rapid shut-off of a tap or e.g.
washing machine solenoid valve.

Peter Able presented the following explanation :
This house, 30 years old, has two water feeds, one for a drinking water tap
and one that drives through a water softener, in the garage, into the house
indirect system. Twice this year the house has been shaken by drumming -
sounds, and feels, like a helicopter just overhead! I've managed to stop it
by opening the drinking water tap for about 10 seconds. What's causing it and
what's the remedy?

You have a tap or valve, where the tap washer is vibration at a
resonant frequency. You need to find out which tap or valve is
partially open at the time you hear the noise and then fix it.

Our kitchen hot tap does it when left near fully open, waiting for the
hot to appear. The noise begins, as the hot appears, which is handy - I
just swing the spout around to the washing up bowl and turn it on full.

On 28/01/2021 18:22, Andy Burns wrote:
Peter Able wrote:

Twice this year the house has been shaken by drumming - sounds, and
feels, like a helicopter just overhead!Â* I've managed to stop it by
opening the drinking water tap for about 10 seconds. What's causing it
and what's the remedy?

Water hammer, can be started by a rapid shut-off of a tap or e.g.
washing machine solenoid valve.

Thanks Andy. This happens when nothing is happening in the house's
plumbing - not even a cistern refilling after a flush. Plus it can't be
relieved by opening any tap but the drinking water feed tap. Nor by
flushing any cistern. I've been down this paths.

It is audible outside the house at, roughly, where the water supply -
both direct and indirect - enters the house.

PA

On 28/01/2021 18:58, Harry Bloomfield wrote:
Peter Able presented the following explanation :
This house, 30 years old, has two water feeds, one for a drinking
water tap and one that drives through a water softener, in the garage,
into the house indirect system.* Twice this year the house has been
shaken by drumming - sounds, and feels, like a helicopter just
overhead!* I've managed to stop it by opening the drinking water tap
for about 10 seconds. What's causing it and what's the remedy?

You have a tap or valve, where the tap washer is vibration at a resonant
frequency. You need to find out which tap or valve is partially open at
the time you hear the noise and then fix it.

Our kitchen hot tap does it when left near fully open, waiting for the
hot to appear. The noise begins, as the hot appears, which is handy - I
just swing the spout around to the washing up bowl and turn it on full.

Thanks, Harry. The resonant frequency is about 10Hz. That is too low,
isn't it? The drinking water feed has a stopcock and then a tap. I've
played with both. The stopcock has no effect, the tap kills the
vibration after about 10s of full on.

PA

On 28/01/2021 20:25, Chris Hogg wrote:
On Thu, 28 Jan 2021 17:59:46 +0000, Peter Able wrote:

This house, 30 years old, has two water feeds, one for a drinking water
tap and one that drives through a water softener, in the garage, into
the house indirect system. Twice this year the house has been shaken by
drumming - sounds, and feels, like a helicopter just overhead! I've
managed to stop it by opening the drinking water tap for about 10
seconds. What's causing it and what's the remedy?

TIA

PA

What others have said, plus you can get hammer if the ball-cock in the
CW tank in the loft starts to 'bounce', i.e. vibrate up and down,
causing the valve itself to open and shut rapidly. Once it starts,
it's self perpetuating. Bending the arm of the ball-cock downwards a
little can help, or gluing a flat baffle (piece of plastic or
aluminium sheet) onto the ball on the underside so there's more
resistance to it bouncing. Even closing down your main stop-tap a bit
can sometimes cure it.


Thanks for that. I'm familiar with ballcock valve instability. This
hammering is not feelable anywhere in the house's indirect system -
even at the indirect's main riser. Perhaps I need to investigate how
the supply pipe splits to provide the separate feeds to the water
softener, garden taps and to the drinking water tap. Trouble is that
the wife panics as it really does sound like a helicopter close
overhead, so I have to act drastically. I'll try to track it from the
house to the garage where the supply pipe enters and feeds to garden
taps, the drinking water tap and the water softener / indirect house
system.

PA

Peter Able wrote:

his happens when nothing is happening in the house's
plumbing - not even a cistern refilling after a flush.

Could be started by a pressure wave coming in from the street, once it
sets up a oscillation e.g. involving a cistern float, it can then
continue by itself.

Can you set it off if you try?

Plus it can't be
relieved by opening any tap but the drinking water feed tap.Â* Nor by
flushing any cistern.Â* I've been down this paths.

You said two separate water feeds, is that literally two pipes coming in
from the street, or just that the drinking water tap is tee'ed off
before the piework continues to the softener, then splits to feed tge
rest of the house from there?

It is audible outside the house at, roughly, where the water supply -
both direct and indirect - enters the house.

As others have suggested, try sligtly closing down your stopcock(s).

On 28/01/2021 17:59, Peter Able wrote:
This house, 30 years old, has two water feeds, one for a drinking water
tap and one that drives through a water softener, in the garage, into
the house indirect system.Â* Twice this year the house has been shaken by
drumming - sounds, and feels, like a helicopter just overhead!Â* I've
managed to stop it by opening the drinking water tap for about 10
seconds. What's causing it and what's the remedy?

TIA

PA

You probably need to install a shock arrestor such as
https://www.screwfix.com/p/reflex-ex...-0-16ltr/8199v
- or maybe a larger one - to absorb the pressure fluctuations and stop
the noise.

The noise is caused by a standing wave which can be triggered by a tap
suddenly shutting, or sometimes by a tap that's slightly open such that
the small flow acts a bit like the mouthpiece of a woodwind instrument,
and the vibrations are amplified by the pipework.

The arrestor adds some resilience into the system which reduces the
resonant frequency to below the audible range.
--
Cheers,
Roger

On 29/01/2021 23:04, Roger Mills wrote:
On 28/01/2021 17:59, Peter Able wrote:
This house, 30 years old, has two water feeds, one for a drinking
water tap and one that drives through a water softener, in the garage,
into the house indirect system.Â* Twice this year the house has been
shaken by drumming - sounds, and feels, like a helicopter just
overhead!Â* I've managed to stop it by opening the drinking water tap
for about 10 seconds. What's causing it and what's the remedy?

TIA

PA

You probably need to install a shock arrestor such as
https://www.screwfix.com/p/reflex-ex...-0-16ltr/8199v
- or maybe a larger one - to absorb the pressure fluctuations and stop
the noise.

The noise is caused by a standing wave which can be triggered by a tap
suddenly shutting, or sometimes by a tap that's slightly open such that
the small flow acts a bit like the mouthpiece of a woodwind instrument,
and the vibrations are amplified by the pipework.

The arrestor adds some resilience into the system which reduces the
resonant frequency to below the audible range.


Thanks, Roger. I guess that a damper may stop this - but I'm left
wondering what has caused this after 33 years of no issues; and where
I'd put it. There's only about 2m of the drinking water feed in the
house. The rest is underground.

When the effect starts again, I'll check to see if the water softener
inlet and output pipes and the road-side meter vibrates !

PA

We had the same trouble a couple of years ago - did all the usual
things without being able to track it down to anything in our house.
Decided it started coincident with some plumbing work in the adjoining
house where a downstairs loo was added - probably with sharp shut-off
taps and valves.
Our mains water pressure is quite high so I fitted a regulator and a
shock arrester just after the internal stopcock.
This improved the hammering but did not completely eliminate it.
A couple of weeks later the plumber re-appeared next door and the
noise has never come back - guess they were suffering too.

Picture here - was just a straight pipe on the left (stainless steel).
https://ibb.co/L80PZfK

On 02/02/2021 16:35, Geo wrote:
We had the same trouble a couple of years ago - did all the usual
things without being able to track it down to anything in our house.
Decided it started coincident with some plumbing work in the adjoining
house where a downstairs loo was added - probably with sharp shut-off
taps and valves.
Our mains water pressure is quite high so I fitted a regulator and a
shock arrester just after the internal stopcock.
This improved the hammering but did not completely eliminate it.
A couple of weeks later the plumber re-appeared next door and the
noise has never come back - guess they were suffering too.

Picture here - was just a straight pipe on the left (stainless steel).
https://ibb.co/L80PZfK


Thanks, Geo. I think that must be the situation here, too. Sod's Law, it
hasn't happened since - but when it does I'll be searching outside.

Our water softener must damp the house - but the drinking water feed
comes off the main before it feeds the softener. The amount of energy
going into the vibration points directly away from the house - and it
was audible outside the house.

PA