Pipes knocking if sink turned on while shower is running


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Old 07-29-16, 08:11 AM
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Pipes knocking if sink turned on while shower is running

Hello,
I have a pipe knocking issue. Pipes behind the wall of the bathroom knock only when someone turns on the sink faucet (hot or cold) while the shower is running. It does not happen when only one or the other is running. Turning off the sink faucet does not stop the knocking - it will continue as long as the shower is running. I can make the knocking stop if I turn the shower water more toward cold (or turn it off). There are two bathrooms with showers on this floor but the issue is limited to only one of the showers. However, turning on the sink faucet in either bathroom starts the knocking. Any help is appreciated!
 
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Old 07-29-16, 06:24 PM
J
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Any recent plumbing work been done?
City or well water?
Checked the pressure?
 
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Old 07-29-16, 08:15 PM
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Welcome to the forums.

Definitely check the water pressure. The home improvement stores carry an easy to attach gauge. It can be screwed directly on to an outside or laundry water faucet

3/4 in. Water Pressure Test Gauge-DP IWTG - The Home Depot
 
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Old 07-30-16, 10:18 AM
Z
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I've found that type of knocking is usually related to a washer going bad. It causes a turbulence in the water, which causes the repeated knocking. The hard part is usually figuring out which washer is the issue. It sounds like it might be one of the shower cartridges, since that's the constant in the equation.
 
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Old 07-30-16, 11:23 AM
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I agree with Furd regarding turbulence being the issue.
The most likely place a washer went bad is in the angle stop valves under the sink.
I would change out all angle stops and supply lines under the sinks. Flush the lines before connecting to faucet.
If your angle stops are in good shape, ensure they are fully open.
 
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Old 07-31-16, 06:32 PM
Z
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Hey! Handyone - who are you giving credit to? I'm pretty sure that was my suggestion!

(of course we still don't know if it'll be the solution)

 
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Old 08-01-16, 05:58 AM
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Further info.

City water. Pressure is fine – recently checked. Recent plumbing work – yes. A plumber just recently replaced the valve in the shower. Prior to that work, the shower was off when the handle was at the 6:00 position and turned counter clockwise to hot at 9:00. Since he worked on it, off is now at 12:00 and the handle turns clockwise only as far as 6:00 - which does not seem to be fully hot. I don’t know if we had the knocking problem prior to that work because we had just moved into the house were not using that shower.
 
 

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