Strange Plumbing Noises: What They Mean and When to Worry

Your pipes are trying to tell you something. Here's how to decode the message.

I'm Justin Sims, and plumbing is supposed to work quietly. When your pipes start making themselves heard, it's usually a sign that something needs attention.

Some noises are harmless quirks. Others are early warnings of expensive problems. Let me help you tell the difference.

Water Hammer: The Loud Bang

**What it sounds like:** A sharp bang or thud when a faucet or valve shuts off suddenly.

What's Happening

When water flows through your pipes and a valve closes quickly, the water's momentum has nowhere to go. It slams to a stop, creating a shockwave that reverberates through the pipes. That's the bang you hear.

Common triggers:

• Washing machine valve closing
• Dishwasher changing cycles
• Quick-close single-handle faucets
• Sprinkler system valves

Is It Serious?

Yes, actually. Water hammer creates pressure spikes that stress your pipes, fittings, and valves. Over time, this can:

• Loosen pipe fittings
• Damage valves and appliances
• In extreme cases, burst pipes

The Fix

**Water hammer arrestors** are the solution. These devices contain an air chamber that absorbs the shock, cushioning the sudden pressure change.

They install at the point of the problem (near the washing machine, for example) and are required by code in new construction. Older homes often lack them.

**DIY option:** Some air chambers can be installed by handy homeowners. More complex installations require a plumber.

**Temporary fix:** Reducing water pressure with a pressure-reducing valve can minimize hammer, though it doesn't eliminate the root cause.

Gurgling Drains: The Bubble Sound

**What it sounds like:** Glug-glug-glug when water drains, or gurgling from one drain when you use another.

What's Happening

Gurgling usually means venting issues. Every drain in your home connects to a vent pipe that goes up through your roof. These vents:

• Allow air into the drain system so water flows smoothly
• Let sewer gases escape safely outside

When a vent is blocked or undersized, draining water creates suction that pulls air through the P-traps of other drains—hence the gurgling.

Other Causes

• **Partial clogs:** Water squeezing past a blockage can create gurgling
• **Main line issues:** Problems in your sewer line can cause multiple drains to gurgle
• **Improper venting:** Older or modified homes sometimes have inadequate venting

Is It Serious?

It's worth investigating. Gurgling from a partial clog will worsen over time. Venting issues can lead to dried-out P-traps and sewer gas entering your home.

The Fix

• **If it's one drain:** Try cleaning that drain and check for partial clogs
• **If multiple drains gurgle:** Likely a venting issue or main line problem—call a plumber
• **If it started after a roof repair:** Check that vent pipes weren't damaged or covered

Whistling or Squealing: The High-Pitched Scream

**What it sounds like:** A whistle, squeal, or high-pitched whine when water is running.

What's Happening

This usually indicates restricted water flow through a small opening. Water forces its way through and creates vibration—like air through a whistle.

Common causes:

• Worn washer in a faucet or valve
• Debris caught in a valve
• Partially closed valve
• Mineral buildup restricting an opening
• Water pressure too high

Is It Serious?

Usually not critical, but the problem will likely worsen. And it's annoying.

The Fix

• **Identify the source:** Run different faucets until you isolate which one causes the whistle
• **Check valves:** Make sure supply valves are fully open
• **Replace worn parts:** Worn washers and cartridges are often the culprit
• **Check pressure:** Very high pressure (above 80 PSI) can cause whistling—a PRV might help

Rattling Pipes: The Vibration

**What it sounds like:** A rattling, clattering, or vibrating noise when water is running.

What's Happening

Your pipes expand and contract with temperature changes and can vibrate when water flows through them. Normally, straps and supports hold them firmly. But when pipes become loose:

• They vibrate against walls, studs, or each other
• Temperature changes cause expansion and contraction noises
• High water pressure makes vibration worse

Is It Serious?

Not immediately dangerous, but persistent vibration can wear on joints and connections over time.

The Fix

• **Access and secure:** If you can access the pipes (basement, crawl space, utility chase), add or tighten pipe straps
• **Insulation:** Foam pipe insulation can dampen vibration and reduce expansion noise
• **Pressure check:** Very high pressure increases vibration—check your PRV

Running Water When Nothing Is On: The Ghost Flush

**What it sounds like:** You hear water running somewhere, but nothing is in use.

What's Happening

Water is flowing somewhere—and unless it's draining properly, it's wasting water and money.

Common sources:

• **Running toilet:** The fill valve cycles to replace water slowly leaking past the flapper
• **Leaking valve:** A stuck or leaking supply valve or fixture
• **Hidden leak:** A pipe leak in a wall, slab, or underground

Is It Serious?

Yes. Even a small continuous leak adds up to significant water waste and potential damage.

The Fix

• **Toilet check:** Do the dye test (food coloring in tank—if it reaches bowl without flushing, flapper is leaking)
• **Isolate:** Turn off fixtures one by one to identify the source
• **Meter test:** Check if your water meter is running with all fixtures off
• **If you can't find it:** Call a plumber for leak detection

Humming or Droning: The Constant Low Tone

**What it sounds like:** A steady hum or drone, often when no water is actively being used.

What's Happening

This often indicates high water pressure—your pipes are vibrating from the constant stress.

Other causes:

• Toilet fill valve malfunctioning
• Water heater issues
• Recirculation pump operating

Is It Serious?

High pressure is hard on your whole plumbing system. Over 80 PSI increases wear on fixtures, appliances, and pipes.

The Fix

• **Check your pressure:** Use a gauge on a hose bib. Above 80 PSI needs attention.
• **Install a PRV:** A pressure-reducing valve protects your system
• **Adjust existing PRV:** If you have one, it might need adjustment

Popping or Rumbling from Water Heater