Let the Natural Handyman help you take the bite out of water hammer!!

Ever hear a banging noise in your water pipes when someone shuts off a faucet? Or when the toilet stops filling? No, it's not the neighbor downstairs letting you know it's time to quiet down. Not this time, anyway!

That bothersome noise is called water hammer.

Water hammer is the sound of moving water being suddenly stopped cold by the closing of a valve. Think of running full speed and suddenly running into a brick wall... Ouch! The force, or inertia, of this water is transferred instantly from the water to the pipe, and then into the fixtures or framing of your home. Or in the case of my example, the pain centers of your bones! If the pipes are loosely or inadequately attached, they may visibly move. Hard to ignore, this hammer-like sound can be heard throughout all your plumbing.

Water hammer is the most pronounced with washing machines and dishwashers, which use quick-acting solenoid shutoff valves. Try flying a jet into that brick wall! However, it can and does occur with toilet valves and plain old faucets as well.

So who cares, you might say... I like the noise! Well, the problem is that water hammer is not only loud but can also be destructive. The force it exerts is hardly subtle... it can even break a poorly soldered joint or fitting! Over time, recurring water hammer can loosen the nailed mounting brackets that attach the pipes to the studs and joists in your home, leading to more movement and greater risk of leakage in joints and fittings.

Before you start, check your pipes for loose supports or straps...

Yes water hammer can cause pipes to loosen from their supports.  But loose pipes can also make noises even with minimal water hammer.  Air chambers and water hammer arrestors don't eliminate 100% of the hammer... just enough to eliminate serious movement.  But there is an assumption that the pipes are securely strapped to supports.

So get down to the basement and observe the pipes when a toilet or other valve turns on and off.  If there is lots of movement, you might want to secure them with new pipe clamps first.  You might find that you don't have a serious water hammer problem after all.

Stop water hammer before it's too late...

Water hammer is controlled by the installation of either permanent air chambers, water hammer arrestors, or both.  (You can even try NH's unpatented Do-It-Yourself Air Chamber described below!)

The permanent air chamber is simply a vertical section of copper pipe with a cap on the end that is attached with a T-fitting to the supply line near a shutoff valve or appliance. They are installed on both hot and cold water lines. The chamber is filled with air which absorbs the force of the moving water by compressing within the chamber, acting like a shock absorber.

These chambers are normally installed within the walls during construction. However, your home may have these air chambers installed and still experience water hammer. Over time the air in the chambers gets absorbed by the water, until there is too little remaining absorb shock.

To refill the chambers with air, it is necessary to completely drain the water from your plumbing system. As the pipes drain, so does the water in the air chambers. The first step is to shut off the main water supply valve. Then open all faucets throughout the house, and flush all toilets. Open the lowest faucet(s) in the house (hot and cold), or a system drain if you have one, and all the water will exit the pipes. Don't forget to turn on the washing machine (set to warm to open both hot and cold valves) and dishwasher for a few moments to be sure their pipes are also fully drained.

NOTE: You may have to drain off some of the water from the hot water tank, if you have one, to fully clear the hot water pipes. See the article on flushing hot water heaters at my website for precautions regarding this process. (You might want to kill two birds with one stone and flush your water heater now, too.)

Build NH's Do-It-Yourself Air Chamber!!

Sometimes, draining down the pipes just doesn't work.  Perhaps the air chambers are blocked so they don't drain... or they don't exist!  And you're not in the mood to open up the walls and investigate.

If that's the case, you can assemble our do-it-yourself air chamber that does not require much plumbing skill AND doesn't require making any holes in the walls!

These two graphics really say it all!  This sample air chamber (left) is designed to fit behind the toilet tank... a typical water hammer culprit.  Basically, the chamber consists of a vertical piece of 3/8" copper tubing sealed at the upper end.  In this case, I used a 3/8" compression tubing connector, replacing one of the compression rings and nuts with a compression cap.  (Be sure to wrap the threads with at least five or six turns of Teflon tape before installing the cap to prevent air leakage.)

A compression "T" is installed above the shutoff valve using a short length of tubing.  The air chamber is connected to the second connection and the toilet inlet tube (or, in this case, no-burst hose) to the third.

As you can see in the "after" photo, the air chamber tubing has been bent to neatly "hide" behind the toilet tank.  Use as long a length of tubing as you can for the chamber.  The longer the air chamber is, the better it will work.  In fact, you can coil it or zig-zag it across the back of the tank for added length... as long as it is above the shutoff and inlet tubes so water can't leak into it (and air leak out of it).

For an even neater and more professional job, use all chrome parts.  It will look positively spiffy and work just as well.  If you can't get chrome tubing, purchase an extra long 3/8" faucet supply tube and cut off as much as you need.

If you have soldering skills, this entire assembly can be soldered into a single piece, needing compression connections only at the shutoff and at the toilet inlet tube!

One caveat.  Because your plumbing is probably 1/2" copper pipe and our DIY air chamber is 3/8" tubing, it will not absorb severe shocks as well as a 1/2" chamber... but it will sure help in most cases!

If that just isn't good enough for you, you can design a similar air chamber by adding a soldered 1/2" T between the shutoff and the wall, or other variation depending on the type of shutoff you have and the amount of visible pipe.  Seriously, if you have the plumbing skills to understand this, you undoubtedly have the creativity to design one of your very own!!

For intense applications or where an air chamber is impractical, enter the mechanical water hammer arrestor...

One problem with air chambers is that they are rather difficult to install in some situations due to space considerations. Enter the water hammer arrestor as an alternative to the air chamber. It may be used in new installations or as an add-on where an air chamber is either impractical, impossible, or inadequate.

Arrestors, such as the one shown at the right, are sealed units that contain a spring and a waterproof air bladder to absorb the force of the moving water. They are available in both residential and commercial capacities, depending on the application. They were invented originally for high pressure, high volume commercial and industrial water systems, which are especially prone to water hammer damage.  In these intensive applications, an air chamber may not supply adequate protection. This is especially true in systems that have both pumps and shutoff valves on the same line.  Now, there are systems available for home use at many plumbing supply houses and home stores.

Arrestors never have to be "recharged" as air chambers do. However, being mechanical devices they will eventually need maintenance or replacement. Air chambers, being non-mechanical, should last the life of your home.

Any fluid that moves through pipes can cause hammering, not just good old "aqua pura". Water hammer arrestors are used throughout the chemical industry to prevent damage to valuable equipment. If you are interested in surfing the web site of a manufacturer of water hammer arrestors for industrial use, visit