Why is My Sump Pump Making Noise? 5 Sounds You Shouldn’t Ignore

A sump pump is designed to be a quiet protector, usually tucked away in a corner of the basement. Under normal conditions, you should hear nothing more than a low, steady hum and a soft click when it engages. However, when your pump starts clanging, grinding, or thumping, it is often a cry for help.

Ignoring these sounds can lead to a mechanical failure at the exact moment you need the pump most. Understanding what these noises mean allows you to address the problem before your basement ends up underwater. Here are the five most common sump pump sounds and how to fix them.

1. Loud Thumping or Banging

If it sounds like someone is hitting your pipes with a hammer every time the pump shuts off, you are likely experiencing "water hammer."

The Cause: When the pump stops, the column of water remaining in the discharge pipe falls back down due to gravity. If the check valve (the one-way valve in the pipe) closes too abruptly, it creates a high-pressure shockwave that shakes the plumbing.
The Solution: Replace your standard swing check valve with a "silent" or "spring-loaded" check valve. These are designed to close more smoothly, eliminating the jarring noise and reducing stress on your pipe joints.

2. Grinding or Screeching

A grinding noise is almost always a mechanical issue involving the internal moving parts of the motor.

The Cause: This usually points to a damaged impeller—the small spinning fan that pushes the water—or worn-out motor bearings. If a small stone or piece of gravel gets sucked into the intake, it can jam the impeller and create a harsh metal-on-metal sound.
The Solution: Turn off the power and inspect the intake screen. If the impeller is visible and bent, or if the noise persists after cleaning, the motor is likely failing. In most cases, a grinding motor is more cost-effective to replace than to repair.

3. Excessive Vibration or Rattling

While all pumps vibrate slightly, excessive shaking that rattles the entire basin is a red flag.

The Cause: The impeller may be out of balance or chipped. Much like a tire on a car, if the impeller loses a small piece, it will wobble at high speeds. Alternatively, the pump might be touching the hard plastic or concrete walls of the sump pit, amplifying the natural vibration.
The Solution: Ensure the pump is centered in the pit and not leaning against the sides. You can also place a specialized rubber "silencer" mat or bricks at the bottom of the pit to help absorb the vibration.

4. Constant Gurgling

If your pump sounds like it’s finishing a drink through a straw, it is likely sucking in air.

The Cause: This occurs when the pump’s shut-off level is set too low, causing it to continue running after the water has already been evacuated. It can also be caused by a clogged "weep hole"—the tiny hole in the discharge pipe that prevents airlock.
The Solution: Adjust the float switch so the pump turns off before the water level drops below the intake. Also, take a small wire or needle and ensure the weep hole in the discharge pipe is clear of debris.

5. Persistent Humming Without Water Movement

A humming sound without the sound of rushing water means the motor is receiving electricity but cannot perform its job.

The Cause: This is often a sign of a "frozen" pump. In winter, the outdoor portion of the discharge pipe can freeze solid, leaving the water with nowhere to go. It can also mean the capacitor is dead or the impeller is completely jammed by a foreign object.
The Solution: Check the discharge outlet outside to ensure it isn't blocked by ice or snow. If the pipe is clear, the pump may have reached the end of its life cycle and can no longer generate the torque needed to spin.

Noise Comparison Chart

Sound	Potential Issue	Urgency
Thumping	Water Hammer / Check Valve	Moderate
Grinding	Damaged Impeller / Bearings	High
Gurgling	Airlock / Float Adjustment	Low
Humming	Jammed Motor / Frozen Pipe	Critical
Rattling	Pipe Vibration / Unbalanced	Moderate

When Silence is Actually a Problem

While we focus on the sounds a pump makes, the most dangerous sound is often no sound at all during a storm. If the water level in your pit is rising and the pump remains silent, you likely have a tripped GFCI outlet or a seized float switch.

Regularly testing your pump by pouring a bucket of water into the pit allows you to hear these noises under "controlled" circumstances rather than during an emergency. Most sump pumps have a lifespan of about 10 years; if yours is nearing that age and making noise, an upgrade is the safest path forward.

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