View Single Post
  #3   Report Post  
Christian McArdle
 
Posts: n/a
Default

To avoid taking up all the floorboards and trying to trace the
poor pipe fixing, can we just reduce the pressure by turning
the main stopcock off a bit? If we do this will it cock up the
combi boiler?


Turning down the stopcock will not reduce the pressure, only the flow rate.
Most importantly, it does it for every tap, even those not causing problems.

The problem occurs because modern taps on a mains pressure system can very
suddenly stop the fast, highly pressurised "slug" of water travelling down
the pipe. This slug then compresses into itself and bounces back, sending
pressure waves through the system.

There are a number of solutions.

1. Don't use flexible tails. They can resonate.
2. Turn down the isolating valves to the taps. This reduces the flow rate
and, hence, the maximum speed (and kinetic energy) of the slug of water that
you're trying to stop.
3. Install water hammer arrestors near the taps.

The last solution is the "correct" one. It is basically a tiny pressure
vessel, usually spring loaded, rather than air balanced, that simply absorbs
the pressure wave from the slug of water over a longer period, making the
shock much longer in duration, but, more importantly, much lower in
magnitude. It needs to be close to the tap for maximum effectiveness.

See part 11355 at http://www.bes.ltd.uk/.

Christian.