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True Trade Path

Diagnostic guide

Banging Pipes

Pipes that rattle, knock, or bang in the walls — distinguish water hammer from thermal expansion and loose pipes.

System
Plumbing
Causes covered
6
You can check
4 without a technician

Stop and read this first

  • Persistent banging can crack solder joints inside walls — fix it before a hidden leak develops.
  • Do not hammer on walls to stop rattling — you can damage the pipe.
  • If banging is accompanied by a leak, shut off the main valve and call a plumber.

Work through these in order

Ordered from most to least likely. Working top down means you rule out the cheap, common causes before paying anyone to look at the expensive, rare ones.

  1. Water hammer from fast-closing valves

    CommonYou can check
    How to check
    A single loud bang when a faucet, toilet, or appliance valve closes quickly.
    The fix
    Install water hammer arrestors on the offending supply lines ($15 to $40 each DIY). See the water hammer guide for full steps.

  2. Loose pipe hangers or straps

    CommonYou can check
    How to check
    Rattling or knocking when water runs, not just when it stops. Pipes vibrate visibly in an unfinished basement.
    The fix
    Secure pipes with straps every 6 to 8 feet. Add foam insulation between pipes and framing members.

  3. Thermal expansion ticking

    CommonNeeds a pro
    How to check
    Ticking or creaking when hot water runs, especially in copper pipes. No bang on valve close.
    The fix
    Normal thermal expansion. An expansion tank on the water heater ($150 to $350) reduces pressure fluctuations if a check valve or PRV is on the main.

  4. High water pressure

    CommonNeeds a pro
    How to check
    Pressure above 80 psi at a hose bib gauge. Multiple fixtures cause noise.
    The fix
    Adjust or replace the pressure reducing valve ($250 to $500). Target 50 to 60 psi.

  5. Air in the water lines

    PossibleYou can check
    How to check
    Sputtering at faucets along with banging. Started after plumbing work or a main shutoff.
    The fix
    Run all faucets starting from the lowest to the highest in the house until water flows smoothly.

  6. Worn faucet washer or cartridge

    PossibleYou can check
    How to check
    Banging at one fixture. Faucet chatters or drips when partially open.
    The fix
    Replace the washer or cartridge ($15 to $50 DIY).

Once you know what it is

Step one

Know what it should cost

Get the range before you call, so the first number you hear is not the only number you have.

Step two

Decide repair or replace

On equipment near end of life, the repair is usually the first of several.

Step three

Check the quote

Compare against the typical range and confirm the terms before you sign.

Whole-House Repiping cost guideRepair or replace calculatorEstimate repair costAnalyze a quote

What the fix costs

Tools for this decision

Other symptoms