Knocking pipes are a plumbing issue that many homeowners may encounter. This clattering or banging noise that sounds kind of like ghostly knocking is usually the manifestation of mechanical problems within your residential plumbing system. This phenomenon can vary in intensity and frequency, from a gentle tap when specific faucets are used, to a loud hammering sound that reverberates throughout the house at all hours.

The primary cause of knocking pipes is usually the change in water pressure or an abrupt end to the water flow, known as water hammer. When a valve closes quickly, the water flow is stopped suddenly, which results in a shockwave moving back through the pipe, causing the pipe to jerk and create a knocking sound. However, other factors can also cause knocking pipes. These include high water pressure, poorly secured pipes, and air chambers or water hammer arrestors that have become waterlogged.

A straightforward and practical approach to rectify knocking pipes is to completely drain your home's plumbing system. This process involves shutting off the main water supply, and then opening all faucets, showers, and water outlets, effectively getting all the water and air out of the system. This can resolve water hammer by clearing out waterlogged air chambers, if they exist in your plumbing system. Best of all, anyone can accomplish this fix; it doesn't require any specialized tools or advanced plumbing knowledge.

Air chambers are a simple and effective design feature meant to prevent water hammer. They function by providing a space for water to expand and compress without causing shockwaves. Over time, however, these chambers can become waterlogged and lose their effectiveness. If your home is equipped with air chambers, restoring them can be as simple as draining your plumbing system.

Loose pipe mounts can cause pipes to rattle and generate noise. It's worth taking the time to inspect any visible pipes in your home for signs of movement or loose mounts. This issue is particularly prevalent in older houses where the plumbing system may not have been serviced or upgraded for many years. If you discover any loose mounts, these can often be tightened with a simple wrench or screwdriver. If draining the pies doesn't work and you do find loose mounts, this can significantly reduce the knocking sounds.

If knocking pipes persist despite your best efforts, it might be time to consider installing water hammer arrestors. These mechanical devices provide a cushion for the shockwave created when the water flow is suddenly stopped. They can be installed on each faucet or valve to absorb the shock and minimize the knocking. While you can undertake this task with a bit of DIY spirit and a comprehensive tutorial, it's always wise to consider seeking professional assistance for optimal installation.

Another reason you might experience knocking pipes is high water pressure. The force of water moving through your pipes may exceed the pipes' capacity, causing them to shake or rattle. You can use a pressure gauge to measure your home's water pressure. If the pressure exceeds the recommended range of 50-70 psi, installing a pressure reducing valve could be a viable solution. Although this task is somewhat complex, homeowners with a reasonable level of plumbing knowledge and access to the right tools can often accomplish it.

While the solutions mentioned so far can be managed by most homeowners, there are instances where it's advisable to call a professional plumber. These situations might include persistent knocking sounds even after attempting the DIY fixes, inaccessible pipes that are concealed in walls or floors, or if you suspect issues with pipe joints or internal pipe damage.

Different types of pipes can produce different kinds of noises. For example, copper pipes are rigid and can be noisier than plastic alternatives such as PVC or PEX, which can absorb vibrations more effectively. If the noise from knocking pipes becomes unbearable, and you're prepared for a more significant plumbing overhaul, replacing your old pipes with these quieter materials could be an effective long-term solution.