DIY Solution to Knocking and Banging Noise from Pipes

Water Hammer Arrestor installed under the sink of a bathroom.
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Ever since we moved into our old house, both sinks in our master bathroom have a tendency to make a loud knocking and banging noise. It happens whenever we shut the faucet water off on both the hot and cold water. And because I've never experienced such noise in the past, the first thought that ran through my mind is the water pipes are old and maybe about to burst! And a burst leaking pipe would be the worst solution resulting in expensive repairs on downtime.

Luckily at the time, I had hired a contractor to pick up and install a washer and dryer from a local store. While he was over, I had him come upstairs to diagnose the sound. Turned out this knocking and banging noise isn't uncommon, and is simply called a water hammer. The basic concept is when the faucet is open, water flows freely from the pipes. However, when the faucet is abruptly shut off, the pressure of the flowing water in the pipes has nowhere to go causing a vibration to occur throughout the pipes. And the easiest way to describe that sound is banging and knocking.

Though I meant to ask, I don't recall if my contractor said if the water hammering effect was bad for longevity of the pipes. The contractor said the solution was to install a water hammer arrester. He then proceeded to show me the installation that the previous owners had installed on pipes connecting the washing machine. He explained inside the house, the arrestor would be installed inside the wall. I immediately realized this would be an expensive fix, and decided against resolving the fix. He followed up by saying one way to minimize water hammer is the slowly turn off the water. In this way, the pressure of the water will be slowly shut down.

Fast forward to present day, despite trying to slowly turn off the water, it's more challenging than I imagined due to fast paced lives. Armed with the terminology "water hammer", I found a plethora of information including many sources stating that water hammers can be the cause of leaks in the pipes. In the house, the most common sources of water hammers in the pipes are faucets, dishwasher, washing machine, and toilets. Luckily, there were tons of simple DIY solutions.

Most common is a small water hammer arrestors that can be installed at the pipes under the sink. It's a simple small device that screws on between the water pipes from the wall and the steel water supply hose to the sink. The water hammer arrestor was only $20 each (would need one arrestor for the hot pipe and cold pipe). This was a complete DIY project. And even if it didn't work, I only invested $20. All I needed for the installation was a pair of pliers.

Turns out installing a water hammer arrestor is one of the easiest DIY projects that audibly noticeable results. In fact, it's working so well I considering order a couple more for a toilet that sometimes has the same knocking and banging noises. If the video doesn't work for you, the DIY installation is simple.

Water Hammer Arrestor Instructions

  1. Turn off the flow of water via the valve on the pipe.
  2. Unscrew the existing steel water supply hose (you may need pliers as it's usually very tight)
  3. Attach the water hammer arrestor (make sure it's tight).
  4. Connect the existing steel water supply hose to the other end of the water hammer arrestor (again, make sure it's tight).

This DIY installation took no more than approximately 5 minutes per water hammer arrestor. The most difficult part was working in tight conditions. It takes a bit of wiggling around to some times loosen some of the pipes. I label this as an Easy DIY installation that most homeowners can do.

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