The most common cause of knocking is what's known as 'water hammer. ' This occurs when high-velocity water in a supply pipe slams into a valve which has been suddenly closed, creating a loud knock or bang, and rattling the pipe.
The sound, or water hammer, is the result of in-line pipes moving and bumping around in their hangers. Hammering can be caused by waterlogged air chambers, clogged chambers, or excess pressure in your plumbing system. It can also be the result of a valve or pipe clog, which can produce a staccato banging sound.
A banging noise may also occur randomly, day or night. The type of piping will affect your noise levels – copper pipe is generally noisier than plastic piping. Most banging pipe problems involver copper pipes. Banging is also more common in hot water pipes than cold water ones because they expand and contract the most.
Most often, it is due to pressure changes or water flow issues inside the pipes. Water rushes with high momentum and speed through pipes. When a faucet or valve is shut off suddenly, the moving water hits a closed valve, which causes a loud bang.
If you're hearing banging noises at random, even while no water is running, it's likely that there's some sediment buildup at the bottom of your water heater. If this is the case, what you're hearing is the resulting reverberations of steam bubbles coming out of that built-up sediment.
Most often, it's your home's plumbing system. Sometimes it's due to fluctuating water pressure issues, loose plumbing pipes, or a faulty valve.
The extreme pressure caused by water hammer can blow out gaskets and cause pipes to suddenly rupture, causing serious injury to anyone nearby.
This can be fixed by draining your plumbing system, which requires turning off the main water valve and opening the highest faucet in your home. Then drain water from the lowest faucet. The chamber should fill up with air once the water is drained and resolve your water hammer problem.
A common cause of water hammer is high water pressure. If your pressure is running near 100 psi, then it's likely the cause of your issue. Normal pressure should be approximately 30 to 55 psi. To solve this problem, consider installing a water pressure regulator.
Ignoring water hammer can ultimately result in the catastrophic failure of your flow system. The long-term effects of water hammer can include: Pump and Flow System Damage.
Also called hydraulic shock, the signs of water hammer include a loud thumping or “hammering” noise from pipes carrying fluid and moderate- to heavy vibrations along the pipe system. Its impact can range from mild or undetectable vibrations to severe and very disruptive pressure shocks.
Enough force from water hammer can even cause pipes to burst. If you hear rattling sounds along with the water hammer, it likely means you have pipes coming loose.
Water hammer is usually caused in high pressure (e.g. mains pressure) water systems either when a tap is turned off quickly, or by fast-acting solenoid valves, which suddenly stop the water moving through the pipes and sets up a shock wave through the water, causing the pipes to vibrate and 'shudder'.
Loose pipe-mounting straps
When pipes aren't properly secured, you may hear the sound of water hammers as the movement of water and shockwaves cause them to jostle against framing and other structures in your walls, floor, and ceiling.
Water hammer can commonly be caused by trapped air inside the system. Air can find its way into your pipework system if empty pipework is filled too quickly. To minimise the risk of air accumulating with the system, ensure pipework is filled slowly to allow air to escape.
Turn your Water On and Off Slowly. This one may seem tedious, but the easiest thing that anyone can do to reduce water hammer in your system is to turn on or shut off your water slowly. Abruptly shutting off the water at your taps or shut off valves will cause the pressure surge, ultimately causing water hammer.
Water hammers and your pipes
It's called a water hammer because it sounds like a loud banging when the pipe rattles. The force of the water sloshing in the pipes is so powerful that joints can weaken and eventually break, causing in-home flooding.
Install water hammer arrestors to eliminate the banging.
Water hammer arrestors have air-filled cylinders that absorb the jolt of a sudden water pressure increase when a valve shuts off.
Wedge a chunk of wood between the pipe and the masonry. Ideally, the chunk of wood will be sturdy enough and wide enough that there is no space between the wood and the pipe and the wood and the masonry. Then, you can use a U-strap to hold the pipe to the wood, further reducing any clatter.
Results of water hammer
Causing heat exchanger equipment failures. Breaking pipe welds and even rupturing piping systems. Causing the failure of pipe supports and guides. Bending internal system mechanisms.
The many materials that make up your house — wood framing, plywood, glass, metal ducts, nails, plumbing pipes — all expand and contract at different rates. When a house cools at night, these materials may move slightly, rubbing against each other and making noises. Occasionally, they'll contract with an audible pop.
This sound usually indicates that there is a water leak either in the ceiling or in the wall. Typically this will show up as a water stain near the source of the leak. Sometimes this sound is related to the thermal expansion of drain lines from cold or hot water running through it.
The water pressure that passes through the loose pipes causes them to bang against the wall, causing that knocking sound you hear. This problem only occurs while the water is running, so if the banging noise stops the moment you shut off your water, it's a good indication that loose pipes are the culprit.