How to Fix Banging Pipes

How to Fix Banging Pipes

Banging pipes — that loud thud or knock when you turn off a faucet or the washing machine stops filling — is called water hammer. It's caused by the momentum of moving water slamming into a closed valve. Here's how to fix it.

Why Pipes Bang

Water flowing through your pipes has momentum. When a valve closes suddenly — especially fast-closing solenoid valves in washing machines and dishwashers — that momentum has nowhere to go. The water slams into the closed valve and sends a pressure shockwave back through the pipe, causing the bang and pipe movement.

Over time, repeated water hammer can:

• Loosen pipe joints and fittings
• Cause pinhole leaks
• Damage appliance valves
• Crack solder joints in copper pipes

Fix 1: Install Water Hammer Arrestors (Most Effective)

👉 Water hammer arrestors for washing machine — 2-pack, 3/4 inch swivel connections. The most common source of water hammer is the washing machine — its solenoid valves close almost instantly.

Installation (10 minutes, no tools):

1. Turn off the hot and cold supply valves behind the washing machine
2. Disconnect the supply hoses from the wall valves
3. Thread the arrestors onto the wall valves (hand-tight)
4. Reconnect the supply hoses to the arrestors
5. Turn water back on and run a wash cycle — the banging should stop immediately

For banging at other locations (under sinks, near dishwashers), install arrestors at the supply valve closest to the noise.

Fix 2: Reduce Water Pressure

High water pressure dramatically amplifies water hammer. Test your pressure:

👉 Water pressure gauge — attach to a hose bib and read. If above 80 PSI, reduce it:

👉 Pressure reducing valve — adjust or replace the PRV to bring pressure to 50–60 PSI. This alone often eliminates water hammer.

Fix 3: Secure Loose Pipes

Pipes that aren't properly strapped to framing will bang against walls and joists when water hammer occurs. Add pipe straps every 4–6 feet on horizontal runs and every 6–8 feet on vertical runs. Use cushioned clamps where pipes contact framing.

Fix 4: Recharge Air Chambers

Older homes have vertical air chambers near fixtures that absorb water hammer. If they've filled with water, recharge them:

1. Turn off the main water supply
2. Open all faucets to drain the system completely
3. Close all faucets
4. Turn the main water back on slowly — air chambers refill automatically

Bottom Line

Fix banging pipes by installing water hammer arrestors at the washing machine — it takes 10 minutes and stops the banging immediately. Also check your water pressure and reduce it if above 80 PSI. Secure any loose pipes to prevent them from banging against framing.