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