Why Your Water Pipes are Knocking & Ways to Stop Them

Our Expert Tips

Do you regularly hear a banging or knocking sound coming from water pipes? It’s easy to ignore the noise if it happens occasionally. However, water pipes knocking consistently will leave you frustrated and can disrupt your day-to-day routine.

There are many reasons for water pipes knocking. As one of Long Beach’s expert plumbers, we’ve seen and can fix these possible causes. We also encourage our customers to address those causes quickly with our help before the knocking leads to serious damage.

Keep reading to learn some common causes of water pipes knocking and what you can do about each one.

Common Causes of Water Pipes Knocking

Water Hammer

When you turn off running water, the rushing water will have nowhere else to go. In some plumbing configurations, the force of the water will slam against the shut-off valve, giving off a sound known as water hammer. If you ignore water hammer long enough, it can damage the valve and other parts of your plumbing system.

To correct the problem, you need to visually inspect your pipework to see if any loose parts are reacting to the water slamming against the shut-off valve. If you can’t find any visibly loose parts, the next step is to check the air chamber.

The air chamber is a vertical fixture found near a faucet in old houses. You can find the chamber in the wall cavity holding together the plumbing connected to your sink or tub. The chamber absorbs the shock from abruptly shutting off rushing water.

Unfortunately, the air chamber system can lose its effectiveness over time. Cleaning the chamber or replacing it can often return it to optimal function. In any case, a professional plumber will know how to evaluate the air chamber in most properties.

Expansion and Contraction

Do you hear your water pipes knocking as soon as the hot water tap comes on? The pipes that make up your plumbing infrastructure could be at fault. Pipes consisting of chlorinated polyvinyl chloride (CPVC) variants are especially prone to knocking.

CPVC pipes will expand and contract when hot water is in use around the home. Therefore, they need adequate room to prevent the knocking sounds. If the pipes run through a tight opening, you’ll hear the knocking sound each time you run hot water through the pipe.

The knocking can become frequent since hot water pipes run to your laundry machines, sinks, and showers. So, expansion is the cause of the knocking sound if you notice any of the following:

  • Knocking sounds only when the hot water tap is open
  • Visibly marked CPVC pipes running from your water heater to appliances

The best solution to this cause of water pipe knocking is to identify the CPVC pipes producing the banging sound and give them more room if necessary. If they can expand without rubbing nearby materials, the noise will disappear quickly. Again, this is a job for professional plumbers alone because it involves cutting into the walls and moving CPVC pipes.

High Water Pressure

The ideal water pressure is between 40 and 80 psi. If the water flow rate in your system is too high, you’ll find the pipes rattling around once you turn on the faucets.

High water pressure is a problem that requires urgent professional attention. The high flow rate of increased water pressure can damage appliances connected to your plumbing system. The rattling movement can also trigger leaks if the pipes are too close together or near the wall.

The knocking noise from water pressure is more subdued than other potential causes. Still, the sound is often loud enough for you to notice. If your water pressure gauge shows higher readings, it’s best to install a pressure-reducing valve.

If you only notice the signs of high water pressure when the hot water is running, consider lowering the hot water temperature a bit. If reducing it doesn’t stop the knocking, installing a hot water expansion tank is the next option. The tank will absorb the excess pressure and protect your pipes from pressure damage.

Sediment Build-Up

Sediment build-up in your water heater can also lead to water pipes knocking. The knocking sound in this scenario will occur randomly, even when you’re not using the faucet. Furthermore, the loudness of the noise will give you the impression that the knocking noise is coming from the pipes in your wall.

In this situation, the sound you hear comes from steam bubbles released by the sediment accumulated at the base of your water heater. Think about how boiling water in a pot often attempts to push up the lid. The heating element for tank water heaters is at the bottom of the tank, where sediments mix with water.

The best way to solve this sediment build-up problem is to flush your water heater. Professional plumbing services will have the right tools and knowledge to get the job done quickly. It’s yet another reason to let professionals deal with the knocking problem.

Loose Supply Pipes

Years of use can loosen the supply pipes delivering hot and cold water to your home. Water passing through these pipes even at normal pressures can cause them to bang against the wall, creating knocking sounds. If the sounds stop when you shut off your faucet, it’s a good sign that loose pipes may be the problem.

Copper pipes are more likely to get noisy. However, some plastic pipes can also make some knocking sounds depending on the installation environment.

To resolve this issue, you can strap the affected pipes to the wall if you can reach them. You’ll need to buy some plumbing straps or clips for the job. Be sure to get three-quarter or half-inch clips, which work with most internal plumbing pipes. You also need to use plastic clips for plastic pipes and copper or plastic strips for copper pipes.

Aim to install a clip for every foot. Use as many clips as possible to ensure adequate strapping. The clips aren’t costly, so you can buy as many as possible.

However, you need to ensure you don’t fasten the strap too tightly. It’s important to allow enough room for contraction and expansion. Otherwise, you’ve only swapped one cause of knocking for another.

For pipes within a wall, you can pad out the areas through which they enter and exit the walls with foam. This insulation may be enough to get rid of the knocking noise.

Wear protective gear if you intend to work on hot water lines. The lines may be hot enough to cause some burn injuries if your hands come into contact with them.

Get Your Plumbing Pipes Checked by Professionals Today

Are your water pipes knocking? Talk to Pride Services today to have them checked out professionally. Our expert technicians can quickly narrow down the cause of the strange noises and ensure you never hear them again. Our highly experienced plumbers are always on hand to restore your home’s plumbing to the perfect condition.

You can always count on us for effective and punctual repairs. Our customers live across Nassau County, NY, and nearby areas. We’ve become one of the leading names for plumbing in the area because we always complete each project to the highest standards.

Our professionalism shines through on all types of plumbing projects. Whether you’re looking to stop water pipes knocking or get burst pipe repair from Pride Services, we will always deliver excellent results. Call us today at 516-528-3432 to book an appointment.

Published: Apr 10, 2022

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