Pipes banging when washing machine fills

[joeb99]

Hi.

When the washing machine starts and stops taking cold water, the pipes under the bathroom floor bangs -- only one bang when the machine starts taking in water, then another bang when the machine stops taking in water, followed by a oscilating sound, like the pipe is wiggling up and down for a second.

From what i can tell, the pipes in the bathroom (under a 3/4in ply floor) are not clipped down properly, and this cannot be changed because i cannot take the floor up, or the ceiling down (to get under the floor from downstairs) the misses would KILL me!

The washing machine is connected to the cold water downstairs about 3m from the main stop tap.

The bathroom cold feed is about 11m pipe length from the stop tap, upstairs.

Why does it bang?

How can i stop it?

Its very loud, if i start the washing machine (on a delay timer etc) to be done when i get up, it starts filling at about 5am, and its loud enough to wake the baby.

Wouldn't be so bad if it was only 2 bangs, but the machine takes some water, stops and rotates, takes more, stops and rotates, etc for about 10 minutes!!

The banging is getting louder as the months go by, and im worried that the pipe movement will result in a weak, eventually.

 

[glasgowgas]

Why does it bang?From what i can tell, the pipes in the bathroom (under a 3/4in ply floor) are not clipped down properly, and this cannot be changed

How can i stop it?From what i can tell, the pipes in the bathroom (under a 3/4in ply floor) are not clipped down properly, and this cannot be changed

 

[joeb99]

But why does it bang? the water in the upstairs pipe shouldn't even be moving, its 11m away.
The water to the machine would, like electric, take the shortest path of least resistance, so 3m from supply cock, not 11m from a closed tap?

<confused>

I really cant take the floor up.

 

[TicklyT]

The solenoid driven water valves in a washing machine operate a lot faster than you can turn a tap. As they snap open or closed they send a shock wave through all your plumbing. In some circumstances it can even travel back up the water main and affect the plumbing in neighbouring houses.

 

[Nige F]

Pressure reducing valve on the incoming main just above the stopcock

 

[joeb99]

Hi guys. Thanks for the responces. I can turn the stop cock down to reduce the pressure, but then the toilets take ages to fill up (i think thats a seperate problem).

Would a check valve or a double check valve (whats the difference when using them?) in line with the upstairs pipe be of any use?

 

[buck51]

Why not try fitting a"shock arrester"

 

[joeb99]

Been looking at pressure reducing valves. Whats a good bar value to use for the washing machine? Might fit one to the incommer of the house as the gas man said the boiler cant heat the water fast enough because the pressure was too high last time he was here (we only get warm water unless you turn the tap down)

2bar? 3bar?