What is Water Hammer and How to Prevent It

Water hammer definition?

A water hammer is a rapid increase in pressure in a pipe due to a sudden flow of water into the pipe. This can result in a loud noise, sometimes called ‘water hammer,’ often accompanied by visible waves of water that may appear on the pipe walls. Water Hammer is very difficult to detect and diagnose because it can be caused by several different factors – i.e. leaks, pipe sizing, and flow rate.

For example, if you turn on your sink faucet, water will begin flowing into the pipes for about 8 seconds before reaching the end and then slowing down to a trickle. If you put several gallons of water into the sink at once and turn on the faucet suddenly, there is a large burst of high pressure in the pipes with little or no flow of water. Water hammers are dangerous because they can rupture plumbing pipes.

Water hammer is a phenomenon in which the flow of water through a pipe gets interrupted by sudden expansion of trapped air within the pipe. The resulting force can cause leaky pipes, burst water pipes and other problems that can damage property and disrupt everyday life.

How does it happen?

Water hammer is most commonly caused by sudden changes in flow rates (such as the opening and closing of a valve) at various points within the hydraulic system, but it can also occur when valves are switched between open and closed position during one pumping stroke. A sudden drop in flow rate causes the high-pressure side to open abruptly and rapidly, reducing the volume on this side and raising that on the low-pressure side. This action creates a vacuum which draws air into the cylinder, where it expands rapidly

Why would water hammer suddenly occur?

Water hammer occurs when a valve opens and the output of a device is suddenly increased. This can result in the sudden increase of pressure on pipes, causing them to leak. Water hammer can also occur when an exhaust valve opens as well, with very high pressure on that pipe leading to it bursting due to increased gas pressure. 

It can also happen at another point in the system if there is a partial vacuum developing, or if there is an undissolved substance, for example water in oil pipelines. The sudden change of pressure causes turbulence in pipes of all kinds, so more serious damage could result than normal because earlier leaks may have been fixed.

What would a potential water hammer situation look like?

It might take less than a second to create a water hammer situation, and the resulting force could be very severe. If you imagine that a person is walking in front of an extremely large water pipe, but not touching it, then you can see how a water hammer may be created if the pressure suddenly drops. The potential damage depends on whether the pipe ruptures or not. When pipes rupture, they get bigger and can cause major disruption to buildings and other infrastructure.

How to Handle it?

In order to prevent water hammer, you must make sure that your plumbing is sized in a manner that allows for proper water flow. If you are not sure if your pipes are properly sized, call a licensed plumber to check your plumbing installation.

Resolving water hammer is tough but not impossible. Here is a simple solution:  

1.  Check if the valve has a time delay. If it does, turn off the air and wait for the valve to open. 

2.  If your house uses electricity, close all other doors and windows to prevent heat from escaping into the air supply.  

3. Place a bucket under the lowest faucet that supplies water to your home just in case water pressure drops or you don’t have enough water pressure to stop the flow of water through the faucet.

When it happens

The first thing to do is to reduce the pressure. You simply turn off the water at the main valve. Turn off your water supply directly at the tap. This will stop the hammering and allow gravity to take over and flow down in a reasonable period of time once you open the valve again.

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