D50
Lv 6
D50 asked in Home & GardenMaintenance & Repairs · 1 month ago

Why do I get a water hammer when I turn on outside faucets?

It started when my water heater was replaced a couple months ago. I drained and refilled the system as instructed by the plumber at that time. I did it again last week to try to eliminate the hammer and it seemed to improve things some. But now it's as bad as ever. It only occurs when the ground level faucets are opened. The house has 3 stories. What should I be looking for?

8 Answers

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  • Anonymous
    4 weeks ago

    You need to install a vertical piece of capped pipe at the noisy location.  It will fill up with air (not water) and act to cushion the hydraulic hammer (shock wave) caused when the valve is abruptly closed.

    We called it a "shock absorber" or "water hammer arrestor".  I have also heard it called an "air chamber". 

    Look up online: 

    Plumbing shock absorber. 

    Plumbing water hammer arrestor. 

    Plumbing air chamber. 

    Closing the main is not the answer.  The air chamber is needed.  Possibly several.  Proper plumbing design in the last century has included them at sinks.

    Source(s): I worked in the plumbing department at an architectural engineering company for two decades.
  • 1 month ago

    The standard now is to have small air tank attached to the water line so the air pressure can damper the hammer when you shut off a water line.  Your old water heater probably had an airspace at the top that did the same thing.  

  • D50
    Lv 6
    1 month ago

    I talked to my plumber who suggested the water pressure is too high. Partially closing the household supply valve seems to have solved the problem.

  • 1 month ago

    Go to the Big Box Store and buy a water hammer arrestor and install it next to water valves that shut off abruptly such as a washing machine. 

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  • 1 month ago

    it's in the cold water supply line [not in the hot water lines] somewhere 'before' the water heater.  The plumber should fix this for free -- he did it when he replaced the water heater.

  • Anonymous
    1 month ago

    Bleed the entire water system in the house.  No luck, get a water hammer arrestor installed.

  • y
    Lv 7
    1 month ago

    Any check valves in your lines?

  • Barry
    Lv 5
    1 month ago

    It may be a loose jumper in a faucet. But one way to cure it is to fit a water hammer arrestor in the pipework. This contains a slug of air which cushions the vibration and eliminates noise.

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