A water hammer is a phenomenon that can occur when plumbing systems have abrupt changes in velocity or pressure. This problem occurs most often when there is a sudden change in operating conditions, such as during a valve operation or when shutting off the water supply to an appliance. Such an event causes the water in the pipes to continue moving after the valve has stopped it.
The result is a brief but extremely powerful shockwave inside the pipe that sounds like hammering. Water hammer arrestors are devices that are installed on plumbing systems to help prevent water hammer and reduce its consequences should it occur. Let’s take a look at what water hammer arrestors are, how they work and why you need one on your home’s plumbing system.
What is a Water Hammer?
When water flows through pipes, there is potential for sound and pressure to build up. This is called a water hammer, and it happens when water flow stops suddenly or changes direction. A water hammer can also occur when a faucet is opened or closed in quick succession.
A water hammer can be like a sonic blast. It can cause your faucets to vibrate and make a loud, banging noise inside your plumbing system. This excess pressure can also damage your plumbing system. Warm housing is the result of excess pressure due to a water hammer. You might notice this as brief bouts of banging sounds that come from your home’s plumbing system when you turn off faucets or showers.
What Is a Water Hammer Arrestor?
A water hammer arrestor is a device installed on the supply lines of water-using appliances such as washing machines and dishwashers.
Water hammer arrestors are similar to surge arrestors used for electric systems. Both devices operate by momentarily closing a valve for a very short time (milliseconds) when a change in pressure or flow is sensed in the lines. The brief interruption of flow allows the pressure or velocity in the lines to equalize without creating a shock wave.
How Water Hammer Occurs
The pressure that builds up in a closed pipe system is always trying to push water towards the lowest point in the system. If you shut off a faucet supplying water to a closed system, the pressure in the system will try to push that water to the faucet, which is now lower. If the system is large enough, the water pressure will build up to the point that it can overcome the normal forces that hold the system together. If the pipe has joints or connections that are not strong enough to withstand this increased pressure, then the excess pressure will cause the pipe to rupture.
How Water Hammer Arrestors Work
A water hammer arrestor uses a spring or a special valve to absorb the pressure of the water built up in the system as a result of the change in water flow. It also has a muffler to reduce noise levels by slowing down the water flow in the pipe. In general, water hammer arrestors are installed at places where sudden changes in water flow are more likely to occur.
These include places where hot water is being supplied to cold pipes, or where an outside water source is being connected to the indoor plumbing system. There are different types of water hammer arrestors. Each type is designed to address a specific situation. For instance, a reduction type is used to control high water pressure in a cold water system. It is installed on the water supply line. Pressure-reducing water hammer arresters are used as a part of the plumbing system where the water supply pressure is greater than the system pressure.
Why Install a Water Hammer Arrestor?
A water hammer arrestor is a device installed on the supply lines of water-using appliances, such as washing machines and dishwashers. When you turn off a faucet or shut off the water supply to an appliance, air often enters the lines. The air must be removed when the water supply is turned back on. If an appliance is drawing water while the air is being removed from a line, the pressure suddenly builds up in the line.
If the pressure buildup reaches the water source while the water is still flowing, it can create a “hammer” effect, causing damage to the pipes. Water hammer arresters are devices that are installed on the supply lines of water-using appliances, such as washing machines, dishwashers, etc.
How to Install Water Hammer Arrestors
Water hammer arrestors are installed in the cold water supply lines near fixtures that are likely to cause water hammers, such as a water heater, dishwasher, washing machine, or outdoor spigot. The arrestor is installed between the cold water supply line and the shutoff valve. It is installed near the water heater if the flow of water may vary.
The arrestor should not be installed inside of a crawl space, basement, or any other area where it will be subjected to high temperatures. The water hammer arrestor is installed on the cold water supply line near the valve. The valve is closed, and the water is turned on at the source. Turn the valve back on while watching the water hammer arrestor. Without this, it will most likely vibrate. If there is no vibration, the arrestor is installed correctly.
We recommend hiring a professional from Ezy-Plumb to install water hammer arrestors in your home.
How to Find & Fix the Cause of Water Hammer ASAP
If you hear hammering noises coming from your plumbing system, it’s likely caused by a water hammer. It’s best to have a professional come out to diagnose the problem. But if you’re curious and want to take a look yourself, start by following the plumbing lines back until you find the point at which the hammering noise is originating. This will be the spot where water is being drawn from the supply line. You can then close the valves (if any) leading into the water line from the point of origin to eliminate the source of water.
Next, open valves leading into the water line from the opposite side of the house. When you’ve eliminated the source of water and have a “pressure vacuum” (no water) in the line, the hammering noise should cease. If it doesn’t, you’ll need to call a plumber to diagnose the issue further.
Summing up
A water hammer arrestor is a device that is installed on the supply lines of water-using appliances, such as washing machines, dishwashers, etc. Whenever you turn off a faucet or shut off the water supply to an appliance, air will often enter the water lines.
The air must be removed when the water supply is turned back on. If an appliance is drawing water while the air is being removed from a line, the pressure suddenly builds up in the line. If the pressure buildup reaches the water source while the water is still flowing, it can create a “hammer” effect, causing damage to the pipes with its force.
