Banging Pipes? Water Hammer Causes, Fixes and Costs

Likely causes

• Fast-closing valves

  Oatey points to washing machines and dishwashers, especially high-efficiency models with quick-closing solenoid valves. Single-handle faucets snapped shut and toilet fill valves can do it too.

• High water pressure

  Oatey says homes with high incoming pressure are more prone to water hammer and recommends a pressure-reducing valve when incoming pressure exceeds 80 psi.

• Loose or unsupported pipes

  Oatey tells plumbers to check for loose supply lines and pipes touching a finished surface. Family Handyman notes repeated shocks can shake pipes loose from their hangers, which makes the noise worse.

• Waterlogged air chambers in older homes

  Older plumbing often has short capped pipes at fixtures that hold a cushion of air. Over time they fill with water and stop absorbing the shock. A plumber can drain the system to restore them, or add arrestors.

• A well pressure tank problem

  On a well, a waterlogged pressure tank can make the pump cycle on and off rapidly and cause banging that arrestors won't fix.

• A worn-out arrestor or pressure-reducing valve

  Family Handyman quotes a plumber noting arrestors can wear out with age, water quality and pressure. A pressure-reducing valve that has failed lets full street pressure into the house.

What you can safely check

1. Find when it bangs

   Note whether the bang follows a faucet closing, the washer or dishwasher filling, or a toilet refilling. Bangs at one appliance point to that valve.

2. Close faucets gently

   If the bang only happens when someone snaps a single-handle faucet shut, closing it more slowly is a free fix.

3. Check your water pressure

   A pressure gauge that screws onto a hose spigot or laundry tap shows the house pressure. Some outdoor spigots are plumbed before the pressure-reducing valve, so a laundry tap gives a truer reading. Readings over 80 psi are high by Oatey's guidance.

4. Rule out the heating system

   If the banging comes from radiators or heating pipes when the heat comes on, it is the heating system, not water hammer. Call a heating technician instead.

5. Look for loose pipes you can see

   In a basement or crawl space, look for pipes that move when water shuts off or rest against joists or ducts. Note where they are rather than strapping pipes yourself.

6. Check for leaks after banging

   Look under sinks, behind the washer and at ceilings below bathrooms for drips or stains.

Avoid these

• Ignoring banging that happens often. Family Handyman notes the force can shake fittings loose and cause leaks.
• Adjusting or replacing a pressure-reducing valve on the main line yourself unless you know how to shut off and drain the system.
• Cutting into walls to find the noise. A plumber can usually locate it from the fixture and the pipe runs.

When to call a pro

• Your water pressure reads over 80 psi.
• The banging is loud or happens with several fixtures.
• Pipes are moving or loose where you can see them.
• You see any leak or water stain near where the noise happens.
• You are on a well and the pump turns on and off rapidly.

Typical repair costs

Arrestors that screw onto washing machine valves are among the easiest fixes. The higher installed prices usually apply when the plumber has to work inside a wall.

Frequently asked questions

Sources

1. Banging Pipes: What the Pros Should Know , Oatey
2. What Are Water Hammer Arrestors? , Family Handyman
3. How Much Does It Cost to Replace a Water Pressure Regulator? , HomeGuide
4. How Much Does a Plumber Cost? , HomeGuide