Cold Water Hammer

[600+]

I know we have a couple of plumbers on here so any help would be much appreciated.

Had to change my kitchen tap about a year ago and since I have had cold water hammering :( Will only stop if you open the cold water fully and will not happen if you have another tap running.

I have tried closing down the main water supply under the sink and that helped but then the water pressure in the shower upstairs was pooh :(

Any ideas? What can I do to sort it out? Is it the tap?

Cheers

[chazzyb]

As I understand it, it's down to a pressure wave being reflected back and forth in the pipe work. Runs of pipes that aren't supported properly don't help at all.

I found this http://www.factsfacts.com/MyHomeRepair/PipeNoises.htm which might be helpful.

[600+]

I've read these docs on the net but all require installation of stuff etc etc.

Question is why would it happen when I changed the tap you see

[rigor]

I've read these docs on the net but all require installation of stuff etc etc.

Question is why would it happen when I changed the tap you see

You've installed a tap with a Poltergeist in it!

HTH ;)

[Razor]

Whip the washer out again and make sure you haven't pinched it and deformed it when you tightened up. The loose pipework is usually where to look otherwise.

I have hot water pipes that creak and groan as they heat up, right under the bath surround. There's no way I'm stripping everything to sort them...

Time to sell house!

[kwak zzr]

our old house used to do it when the stop tap wasnt fully open.

[600+]

I shall take the tap off in the weekend and check the washers

[dirtydog]

As Razor said check the tap washer and that the pipe is properly clipped to the wall

[timwilky]

Water hammers can be impressive. We had one cause a major outage at a power station in India when it fractured cooling water pipes. simple because a valve shut too quickly

[Sid Squid]

Generally it's down to insufficient pipe support, it can be worsened by ceramic disc taps - they shut quite abruptly and cause the quick static pressure rise that sometimes causes the hammer in pipework that can move.

If the pipes can't be suitably fixed, there are devices that can be fitted to the incoming main to reduce hammer, essentially they're in two forms:
1) A pressure reducing balanced valve, like the regulator on a gas bottle or a DV if you're a diver, (Jaques Cousteau apparently used a modified camping gas regulator for his first experiments in Scuba breathing apparatus).
2) A piston in a pipe with a spring behind it, when the pressure rises as a valve is shut the piston displaces and the slows the static pressure rise.

[600+]

cheers Sid - because it is not happening in any other house on my street I believe it is sthing to do with the tap so i'll give the washers a try first

[Jelster]

Squidster, the font of all knowledge for anything that's mechanical :D

Generally it's down to insufficient pipe support, it can be worsened by ceramic disc taps - they shut quite abruptly and cause the quick static pressure rise that sometimes causes the hammer in pipework that can move.

If the pipes can't be suitably fixed, there are devices that can be fitted to the incoming main to reduce hammer, essentially they're in two forms:
1) A pressure reducing balanced valve, like the regulator on a gas bottle or a DV if you're a diver, (Jaques Cousteau apparently used a modified camping gas regulator for his first experiments in Scuba breathing apparatus).
2) A piston in a pipe with a spring behind it, when the pressure rises as a valve is shut the piston displaces and the slows the static pressure rise.

[Tris]

Generally it's down to insufficient pipe support, it can be worsened by ceramic disc taps - they shut quite abruptly and cause the quick static pressure rise that sometimes causes the hammer in pipework that can move.

If the pipes can't be suitably fixed, there are devices that can be fitted to the incoming main to reduce hammer, essentially they're in two forms:
1) A pressure reducing balanced valve, like the regulator on a gas bottle or a DV if you're a diver, (Jaques Cousteau apparently used a modified camping gas regulator for his first experiments in Scuba breathing apparatus).
2) A piston in a pipe with a spring behind it, when the pressure rises as a valve is shut the piston displaces and the slows the static pressure rise.

Alternativly, take a "T" off the cold water supply and connect it to a 80 foot pipe that sticks straight up in the air

But on second thoughts Sids idea is tidier :)

[chazzyb]

Alternativly, take a "T" off the cold water supply and connect it to a 80 foot pipe that sticks straight up in the air


Great idea! But what happens when the reservoir is more than 80' above you? Mmmm...:p

[embee]

If all else fails with the tap, you may need a shock arrestor, especially if the tap is at the end of a long pipe run. Sometimes just a different type of tap design with the pipework you have will cause the jumper to vibrate, it happens.

Something like a Watts Micron Shock Arrestor, http://www.lunns.net/ , usually around £20 inc. might do the trick.

Washing machines etc are usual culprits for causing a shock with a sudden shut off.

If it's a vibration then it's often inadequate pipe supports.