Water Hammer ???

[ORIONDAN]

Evening all,
For the last couple of months Ive had a problem from my cold water when the washing machine is on. Whenever the machine is on and I turn on a cold tap there is a knocking sound. Just recently this happened and the water ran yellow/green then was ok again. I drained down and replaced the head of the stopcock and seemed to stop the knocking when 2 taps are on but not the washing machine. Every time this happens I have to drain down to get rid of air locks. Ive looked up a few things and I understand it could be water hammer and the washing machine needs an arrestor but most water hammer seems to happen when a valve is turned off not whilst running, is this true?

 

[Cds]

Water hammer is caused when a valve is suddenly closed against a flow. This sudden closing causes a shock wave travelling at the speed of sound to travel away from the valve until it meets an obstruction, bend or fitting, and then is reflected back. This movement of the wave bouncing between two points resulting in the hammering noise associated with water hammer.

The shock arrestor absorbs the energy of the wave so stopping it.

What you have does not sound like water hammer as this wouldnot result in air locks.

 

[ORIONDAN]

Dont suppose you know what it is and how it can be treated?

 

[chris watkins]

Toolstation > Plumbing > Valves > Mini-Rester
Get a plumber to install one of these, which should do the trick.

 

[Cds]

Chris if it is water hammer then that will do the trick but why would the OP be getting air lock problems?

 

[chris watkins]

Chris if it is water hammer then that will do the trick but why would the OP be getting air lock problems?

You are quite right that will teach me not to read the full post before opening my big gob. sorry to you both. Only thing I can suggest is check for pressure in balance between hot & cold ? ORIONDAN can you tell us where the hot & cold are fed from ? why did you replace the stop valve is this on the mains supply ? & lastly why do you have to drain down to clear air lock normally you would need to use pressure to clear?

 

[ORIONDAN]

I tried many things before taking the stop valve head out but this was the only thing which worked. The stop valve is on the mains supply, I took the head/spindle off and replaced it again, this got the water flowing again but as soon as the washing machine was turned on the pipes started knocking and then no water, took the head off again and replaced and pressure was back, this time have not used the washing machine incase it was causing damage.

 

[chris watkins]

I tried many things before taking the stop valve head out but this was the only thing which worked. The stop valve is on the mains supply, I took the head/spindle off and replaced it again, this got the water flowing again but as soon as the washing machine was turned on the pipes started knocking and then no water, took the head off again and replaced and pressure was back, this time have not used the washing machine incase it was causing damage.

So the washing machine cold supply is off of the mains supply how about the hot ? or is it a cold fill only ?
I have an idea what it may be if this seems to be related to the stop valve, can you check something for me every stop valve has a directional arrow cast on the body of the valve can you check to make sure the valve has not been installed the wrong way around water should flow in the direction of the arrow only ? if you can't see the arrow look for the bit in front of the spindle or if you can take a photo of it & post it.

 

[ORIONDAN]

Thanks, the WM is cold feed only, the arrow is pointing upwards however im presuming the mains comes out of the floor as it is enclosed in a cupboard!

 

[chris watkins]

So as far as you know the arrow points in the direction of flow & the mains pipe carries on to other fittings ? When you took the stop valve apart was the jumper plate loose that is the plate that the rubber washer sits on, did it come out of the end of the spindle ? They should be able to turn but not come out.
The only thing I can think of is that the jumper is loose (& or the stop valve is round the wrong way) when the washing machine fills & the solenoid closes (which they do with a bang) it is sending shock waves down to the stop valve or another fitting & holding it closed. You then have to drain down or at least take the pressure off to free it & allow normal operation.
I would suggest you get your plumbing checked out along these lines, I would fit a shock arrestor if you can hear this bang as the WM stops filling & possibly replace the stop valve with a full bore lever ball valve which do not have a washer.
Hope this helps, let us know how you get on.

 

[ORIONDAN]

Thanks, yes the first time I took the head off the jumper was loose so I replaced the whole spindle with a new one which worked until the WM was used. I have already bought a arrestor to fit on the WM which should be here today so I will let you know, if it does not solve Il replace with a full valve.

 

[chris watkins]

Thanks, yes the first time I took the head off the jumper was loose so I replaced the whole spindle with a new one which worked until the WM was used. I have already bought a arrestor to fit on the WM which should be here today so I will let you know, if it does not solve Il replace with a full valve.

Let us know what happens
Chris

 

[Bernie2]

Have you checked the fill hose filter? Washing machines can fill in different ways internally. Some old ones even have an air gap and float, which if sticking could possibly cause water hammer.

 

[Phil]

Evening all,
For the last couple of months Ive had a problem from my cold water when the washing machine is on. Whenever the machine is on and I turn on a cold tap there is a knocking sound. Just recently this happened and the water ran yellow/green then was ok again. I drained down and replaced the head of the stopcock and seemed to stop the knocking when 2 taps are on but not the washing machine. Every time this happens I have to drain down to get rid of air locks. Ive looked up a few things and I understand it could be water hammer and the washing machine needs an arrestor but most water hammer seems to happen when a valve is turned off not whilst running, is this true?

You get this if there are deadlegs in the pipework eg/ lengths of pipe going nowhere and capped off causing water to stagnate. Although the upside to this is air is trapped at the end which should in this case cushion the water hammer.

What boiler is currently in? Combi?

 

[ORIONDAN]

Ok, on Sat the mini arrestor came and I fitted it to the WM hose, since then I believe it has solved the problem as any sink/shower can be used whilst it is running and filling up and hasnt come back all weekend, so thanks everyone for your help.