Water hammer when turning on taps

[Tyrone3117]

I'm getting water hammer in three cold water taps when turning on. If hot water is also turned on there is no water hammer. Previously I was getting all sorts of noises from the pipes even when no taps were turned on. I ran all the hot water from the hot water system via the hot water tap nearest the hot water system and that stopped it. However I am still getting water hammer when turning on the taps. It seems to be associated with the hot water system.

 

[Deleted member 120897]

Do you have a cold water storage cistern and a hot water cylinder?

 

[PlumbDawg]

Have you checked the water pressure? Sounds like me the hot water is decreasing the pressure of ongoing water affecting the flow rate. Could try turning on frontal taps and see if that changes the water hammer.
also how old is the house you are talking about?

 

[Tyrone3117]

I eventually fixed it. However it has started again and I can't remember how I fixed it. I was turning taps on and off in a certain sequence. It's definately associated with the hot water system. Turning off the tap to the hot water system stops the water hammer.

 

[oz-plumber]

If you have a storage cylinder the main culprits for water hammer are:

• Tap Washers. Old worn ones can bounce when the edges get round instead of square.
• Water pressure - if you haven't got a 500 kPa valve installed on the cold water main you may have pressure up to double that.
• Cold water valve at inlet of HWS. They have a spring loaded non return setup. The way the valves are made, if the washer or spring gets wrecked, it can cause the washer to bounce around.

These generally happen when only a little water passes through the tap. If you open the tap fully, water hammer doesn't occur.

Hope this helps

 

[Tyrone3117]

I replaced the valve on the tap closest to the hot water system however it had no effect. I tend to think it's the cold water isolation valve on the hot water system. What's involved in replacing this washer?

 

[oz-plumber]

You can't replace washer in these valves, replace the valve.