Knocking pipe sound - Washing machine?

Question

Hello,

I've connected a washing machine to my cold water supply (blue tap) under my sink. The machine works fine except that when I now turn on the cold water tap at the sink I get a knocking sound. If I turn off the blue cold water valve to the washing machine the knocking sound goes away. Why?

Please can someone explain how I can get rid of this.

Thanks in advance for any advice,
Jason

LITTLE MAMA - What do I do to get rid of this? If I take off the pipe and then reconnect surely I stand equal chance of air getting back into the pipe?

Help!

SENSIBLE_MAN, can I cure this?

Answer 1

Houghton weaver has it right, turn the water pressure down at the stopcock, also worth securing the pipe work in the vicinity, loose pipes move with the surge.

Answer 2

your water pressure is to high read this
Water hammer is a very loud banging, knocking or hammering noise in the pipes that occurs when the flow is suddenly turned off. It is caused by a pressure or shock wave that travels faster than the speed of sound through the pipes, brought on by a sudden stop in the velocity of the water, or a change in the direction. It's also been described as a rumbling, shaking vibration in the pipes.

You might hear water hammer when the clothes washer stops filling, the sprinkler system shuts off or shifts to another zone, when the dishwasher changes wash cycles, or when a faucet is turned off suddenly. It exerts very great instantaneous pressures that can reach excesses of 1000 psi and over time can potentially damage the system by weakening joints and valves causing leaks or even ruptures in the pipes.

Several factors can contribute to water hammer such as:

Improperly sized piping in relation to water flow velocity High water pressure with no pressure-reducing valve Straight runs that are too long without bends; Poor strapping of piping system to structure

hope this helps

Answer 3

when youv'e pushed the washing machine in place you have pushed the pipes against each other or against something. check under the sink unit first. when youv'e found out where its knocking tie something around it like an old piece of towling and knocking will stop. or just try clipping the pipes back to the wall.

Answer 4

definetly water hammer!! what happens when you turn on your cold tap is you releive the pressure from your cold fill pipe on your washing machine then when you turn it of again the pressure builds up again and suddenly stops causing a hammer noise!!
the cure for this is NOT to turn your stop co..ck down as this only releives flow rate not pressure the definitive way to stop this happening without losing flow rate is to fit a pressure reducing valve to your incoming mains supply thus stopping a pressure build up within your cold water system should cost around £30-£40 for the valve and an hours labour for a plumber to fit..

Answer 5

sound like an air gap.....
depend on how the water tap and connection for washing machine is set up try moving the connection around a bit
as there sound like air being let in to the connection via the washing machine ....
if it a Y space connector have the tap connector on the bottom and the and the washer on the top....

Answer 6

sounds to me like the noise you hear is the hot water pipe heating up and expanding after cooling off all night maybe some pipe insulation might help.

Answer 7

Sounds like you have back pressure from the washing machine.

Cure, not sure.

Answer 8

You are sucking air into the waterline. This is why washing machine water taps are "above" the machine. When the washer calls for water a valve opens (in the machine) and allows the proper amount of water to enter. The water is guided to the drum. This leaves an air gap in the line. When you open the tap for the sink, you suck the air into the water line.

Answer 9

Sounds like air in the pipe to the washer.

Answer 10

it could just be loose pipework,the pressure from cold tap is greater than hot,try opening the tap slowly to see what happens.if not trace the pipework back to washing machine to see if anys loose