Water hammers, also known as hydraulic shocks, are surges of pressure that occur when water in a pipeline system suddenly changes direction. When these occur in your home plumbing system, they usually make loud, annoying bangs. Aside from the noise, they can cause your pipes to vibrate violently and even damage them to the point of causing perforations or bursts at pipe seams, causing water damage and possible flooding in bathrooms, laundry rooms, and basements.
Thankfully, water hammer arrestors can be purchased and installed on your existing plumbing system to combat this problem.
Houses more than 25 years old are the most likely candidates for water hammer, as the only method used to manage water pressure when these homes were built was to install vertical pipe risers along horizontal pipe runs at 24" intervals. Over a long period of time, these vertical pipes can fill with water, creating an ideal breeding ground for bacteria that may end up contaminating your home's drinkable water.
The three common types of water hammer arrestors used in residential water pipe systems are explained in detail below.
1. Single Chamber Water Hammer Arrestor
Most often used on 1/2-inch pipe systems, the single chamber water hammer arrestor is easily installed onto any section of pipe where it is needed. Its sealed air chamber absorbs the energy from water pipe pressure surges, staying dry and moisture-free. These arrestors are made of copper and sustain water temperatures up to 180ºF.
Single chamber arrestors are also available for 3/4-inch and 1-inch water pipes, and they can be installed at any angle to the main pipe. If a threaded joint is not available to attach the arrestor, it can be soldered into place on a T-joint and fitted into the existing water pipe while still taking up little space behind the wall panel.
Single chamber water hammer arrestors can be priced as low as $15.
2. Mini End Stop Water Hammer Arrestor
This type of water hammer arrestor comes with a 90-degree angled fitting and a threaded end. It is designed to be directly attached to the hose connection of a washing machine, dishwasher, or other water-using appliance. It can also be used on 1/2-inch, 3/4-inch, and 1-inch diameter water pipes. They can be screwed to a threaded fitting or soldered directly into the pipe itself.
While these water hammer arrestors work best when installed at 90 degrees to the main pipe, their watertight inner chambers will eliminate water hammer at any angle. Like the single chamber option, mini end arrestors only need minimal space behind any interior wall.
Pricing for these arrestors vary depending on the diameter, with 3/8-inch and 5/8-inch fittings selling for as low as $15. However, other sizes can range from $30-40.
3. Hose Bib Style Water Hammer Arrestor
This style of water hammer arrestor has a 6-inch wide PVC housing with an internal diaphragm to disperse the shock of water flowing through a quick-closing valve. These are ideally suited to be attached directly to the water intake on a washing machine, as they can handle high water volumes and higher water pressures than the other two models. They are not suited for installation inside a wall due to their large diameter.
As another point of contrast, getting a hose bib water hammer arrestor can cost up to $125, with additional costs incurring later from installation fees. You can purchase water hammer arrestors and their accessories at any building supply, hardware, or plumbing specialty store.
TIP: Buy and install one water hammer arrestor for every 20' of horizontal water pipe in your home.