Taking Care of Noisy Water Pipes
Did you ever turn off a faucet only to experience sounds and vibrations similar to those produced by a three-point earthquake? Here is what happens. Imagine a fast moving stream of water traveling down a narrow pipe. Suddenly and unexpectedly the water finds a closed valve in place of what, moments earlier, was an escape point. All of a sudden the water within has nowhere to go. An important fact to remember here is that whether the water source is a well, a local storage tank or a community system, the one fact remains – water doesn’t compress. As it comes to an abrupt stop a loud thud results that, and more often than not, it can be heard throughout the entire house. The deafening sound is known as a “water hammer”. And rightly so. The hammering action that creates the horrible racket is actually capable of damaging joints and connections in the pipe – thus this column is worth your careful and considerate attention.
So, why doesn’t your plumbing system make a loud noise each and every time a fixture is turned off? First of all, not every water valve closes quickly. In fact, most valves close slowly enough to prevent water hammer. But even the best laid plans of mice and men can fail. As gaskets in a faucet get old and brittle they can cause the faucet to close more quickly – and a water hammer can result.
Air chambers are added to the plumbing system when it is first installed to act as cushions to prevent water from slamming against the piping. Since air compresses it absorbs the shock of the fast moving water before it has a chance to slam against the end of the pipe. Many household plumbing systems have air chambers built into them at critical locations — like the clothes washer and dishwasher — where electric shut-off valves close rapidly. In some homes air chambers are located at every location where water is turned on and off – even the toilet. Most of the time you can’t see air chambers because they are hidden within the wall with the rest of the pipes.
An air chamber is a vertical pipe located in the wall cavity at the point near a faucet or valve where the water supply pipe exits the wall. The pipe that makes up the actual air chamber usually terminates about twelve-inches above the point where the supply pipe exits the wall. Although they remain concealed in the wall, air chambers are close enough to the fixture to properly cushion the water. The air chamber acts as if it were an upside-down water glass. Once filled with air it becomes a perfect cushion. In copper systems a one piece pipe called a closed nipple is used to make air chambers and since they are one piece there is no place for the air leak, thus these are the most dependable kind. In older systems that use threaded pipe the air chamber is made from a capped nipple. Here there is the chance that air can leak from the cap allowing the air chamber to fill will water rendering it useless and making a once quiet, functional water supply system noisy and prone to damage.
The most common way to eliminate a water hammer is to replenish all air chamber with air. You can’t inspect the air chambers, so this procedure is a must. Here is how to do it. First, shut off your home’s main water supply valve. Next, open a few faucets inside your house. Then, find the faucet on the property that it located at a lower elevation than all the rest – usually outside. Turn it on to completely drain all water from the pipes. Some folks incorrectly refer to this as “bleeding” the system. Normally, when you bleed a system it is in an attempt to REMOVE AIR. In this case we want to ADD AIR. As the water is drained from the pipes it is automatically replaced by air – this includes the air chambers. The moment the water is completely drained from the piping the lowest faucet should be turned off and the main valve reopened. Air will be pushed out of the horizontal and open vertical water lines and will sputter as it exits the faucets inside. However, air will remain in the upside-down air chambers. And in most instances, this procedure will eliminate a water hammer.
Sometimes a water hammer can occur when there is a loose pipe mounting strap. A loose pipe strap can allow the pipe to move freely vibrate against framing members as water is turned on and off. This can happen even if all the air chamber are in good shape. So, make sure to check all accessible pipes to insure that they are properly and tightly connected.
By the way, there is another kind of air chamber called a shock absorber. A shock absorber is an air chamber that is fitted with a gas filled bladder that is connected to a piston. They say that the bladder will not leak and therefore is supposed to last forever. It is our opinion that the fewer mechanical devices in your plumbing system the better. A simple conventional air chamber can be refilled with air in a few minutes – who needs pistons!?! And, good luck!