How to Fix Noisy Pipes (Banging, Hammering, Whistling)
Different sounds mean different problems. Here’s the diagnosis guide.
TL;DR
Banging/hammering = water hammer (install hammer arrestors). Whistling = high pressure or partially closed valve. Knocking = thermal expansion. Squeaking = ungasketed pipes contacting framing.
What’s in this guide
- Identify the sound
- Water hammer fix
- Pressure issues
- Thermal noise
Different pipe noises indicate different problems. Diagnosing correctly leads to fast fixes.
Tools & Materials You’ll Need
Tools
- Pressure gauge
- Adjustable wrench
- Penetrating oil
Materials
- Hammer arrestors ($15 each)
- Pipe insulation
Step-by-Step Instructions
Identify the Sound
Loud bang when faucet shuts off = water hammer. Constant whistle when faucet runs = restricted flow or high pressure. Knocking with heat cycles = thermal expansion. Squeaking when fixtures used = pipe friction in framing.
Fix Water Hammer
Install hammer arrestors at fixtures with quick-closing valves (washing machine, dishwasher, ice maker). Screw onto the supply line at each location. They contain a small air chamber that absorbs the shock when valves close.
Diagnose Pressure-Related Whistling
Test static pressure at hose bib. Above 80 PSI = need PRV adjustment or replacement. 65–80 PSI but whistling = partially closed valve somewhere. Open all shutoffs fully.
Address Thermal Expansion Knocking
Knocking with hot water flow = pipes heating and expanding against framing. Solution: pipe insulation foam to absorb expansion. Or, in severe cases, an expansion tank.
Quiet Pipe Friction
Ungasketed pipes through framing rub against wood. Squeaking when fixtures run. Wrap exposed pipe with foam pipe insulation where it passes through framing. Cushioned saddle straps help too.
The most overlooked cause of “noisy pipes” is high water pressure (80+ PSI). Replace the PRV first if your home is over 8 years old — most LA noise complaints disappear with a properly working PRV.
Constant loud banging needs immediate attention
Severe water hammer can crack pipe joints over time. Address quickly.
Real Scenarios from Our LA Service Calls
Whistling for years
Owner had been hearing high-pitched whistle from supply lines for 3+ years. Static pressure measured 88 PSI (over code limit). Replaced failed PRV. Whistle stopped immediately, prevented likely future supply line failures.
When to Call a Plumber Instead
DIY isn’t always the right call. Bring in a licensed plumber if any of these apply:
- Persistent banging after arrestors installed
- Pressure issues requiring PRV work
- Thermal expansion in walls (need expansion tank install)
Frequently Asked Questions
What is water hammer?
Pressure shock when fast-closing valve stops flowing water. Causes loud bang.
How long do hammer arrestors last?
10–15 years. Some need replacement after losing their air charge.
Will reducing pressure quiet pipes?
Often yes. 60–65 PSI is much quieter than 85 PSI.
Can pipes be too quiet?
No — quiet pipes mean a healthy system.
Is whistling ever just normal?
Brief whistle when valve barely closed = normal. Constant whistle during flow = abnormal.
Need professional help in Los Angeles?
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Call (818) 938-8660
