What's That Knocking Sound in My Pipes? Understanding Water Hammer

If your pipes bang or knock every time you shut off a faucet or your washing machine finishes a cycle, you're hearing what plumbers call water hammer. It's that sudden thud of rushing water slamming to a stop, and while it might seem harmless, over time it can loosen joints and wear down your plumbing. The good news is it's usually fixable.

This is a common complaint in homes of all ages, and pinpointing the cause is the first step to peace and quiet.

Reviewed by our experts

Steve is an experienced plumbing technician and part of our team, with more than 10 years of professional service in Massachusetts and New Hampshire. He specializes in plumbing services, water quality, and heating.

Why It Happens

• High water pressure. When pressure runs too high, water moves through your pipes with extra force, so it hits harder when a valve shuts.

• Improperly supported pipes. Pipes that aren't strapped down securely have room to move. When the water stops short, they knock against the framing and each other.

• A failed expansion tank or pressure-reducing valve. These parts are meant to absorb pressure spikes and keep your system steady. When they wear out, that cushion disappears and the banging returns.

How to Quiet It Down

• Reset the air chambers. Many homes have air chambers behind the walls that cushion the water's stop, and they can fill with water over time. To reset them, shut off your main water valve, open the highest and lowest faucets in the house to drain the system fully, then close them and turn the water back on. The chambers refill with air, and the knocking often disappears.

• Secure loose pipes. Where you can reach exposed pipes, in the basement or under sinks, add cushioned pipe straps every few feet where they run along framing. The padding stops the rattle without pinching the pipe.

• Check your pressure. If your water pressure is running high, a pressure regulator can ease the strain.

Ready for a Fresh Start?

If the knocking won't quit or you're worried about the strain on your pipes, the team at Fagundes Plumbing Heating AC is here to give you an honest assessment. We treat every home as if it were our own, helping you find the perfect balance between comfort and cost. Give us a call at (978) 350-5522  to discuss your options and see how we can keep your home running smoothly.

Fix It With Fagundes

We believe that every family deserves a comfortable, stress-free home where they can truly unwind. Whether it's a simple repair or a brand-new installation, we're dedicated to providing the neighborly care and expert service that keeps your home just the way you like it.