Hearing knocking or banging sounds from your water pipes? Whether the noise shows up when you turn the water on or off, or even when no water is running at all, plumbing noises often point to specific issues within your system. Understanding the common causes and fixes can help you decide when it’s a simple DIY task — and when you should call Moyer Plumbing for professional help.
Common Causes of Knocking Water Pipes
1. Water Hammer (Hydraulic Shock)
One of the most frequent reasons for loud knocking is water hammer. This happens when a faucet or valve shuts off suddenly, forcing moving water to stop abruptly. The surge creates a shockwave that reverberates through the plumbing and sounds like a knock or bang. Over time, repeated water hammer can damage fittings or joints.
Signs: Loud bang right after running water or shutting off appliances like dishwashers or washing machines.
2. Thermal Expansion and Contraction
Pipes naturally expand when hot water flows through them and contract as they cool. This movement — especially in metal pipes — can make popping, ticking, or knocking noises as the pipe rubs against wood framing or joists.
Typical with: Hot water use (showers, dishwashers).
3. High Water Pressure
Too much pressure in your plumbing system can cause pipes to vibrate or knock as water rushes through them. This not only makes noise but can shorten the life of fixtures and appliances.
Normal home water pressure: 40–80 PSI. If yours is higher, it’s time for a pressure check.
4. Loose or Unsecured Pipes
If pipes are not fastened securely to framing or supports, the force of moving water can cause them to shift or strike nearby surfaces — creating a rattling or knocking sound.
Tip: Visible pipes can often be secured with clips or straps. Hidden pipes usually require a pro.
5. Trapped Air in Pipes
Air pockets can get trapped in your plumbing system after repairs, water service interruptions, or even over time. When water pushes trapped air through the pipes, it can create a knocking or banging noise until the air is flushed out.
Solutions That Can Resolve Knocking Water Pipes
Here are some practical steps homeowners can try before calling a plumber:
- Install Water Hammer Arrestors: These devices absorb shock from sudden water stoppage and are especially helpful in systems prone to water hammer.
- Secure Loose Pipes: Use pipe straps or clips to fasten exposed pipes tightly to framing. If pipes are inside walls, a plumbing professional can access them safely.
- Adjust or Install a Pressure Regulator: If water pressure is too high, a pressure reducer or tank installation can stabilize flow and reduce noise.
- Flush Your Water Heater: Sediment buildup in your water heater can cause noise that sounds like knocking pipes. Flushing the heater at least once a year can help prevent this.
- Bleed the Plumbing System: If air is the culprit, briefly draining the system — by shutting off water and opening all faucets — can allow air pockets to escape and restore smooth water flow.
When to Call Moyer Plumbing
If the knocking persists despite basic troubleshooting, or if you’re unsure what’s causing the noise, it’s best to let a licensed plumber take a look. Persistent knocking can sometimes signal deeper issues with water pressure regulators, old pipes, or fixtures that require professional attention.
Moyer Plumbing can diagnose the cause quickly and recommend the right solution — whether it’s tightening loose lines, installing arrestors, adjusting pressure systems, or more extensive repairs.
