Silent Water Hammer Causes More Damage Than Loud Water Hammer

First, I will get right to the point. If you replace your washing machine hoses you should add water hammer arresters (shock absorbers). I will provide a picture of my favorite below. Later, I will provide plenty of details.


Also, my favorite hoses come with built in elbows. I will provide a photo of them below. Unlike most manufacturers that refer to their hoses as five year hoses, this manufacturer calls them lifetime hoses. 

Okay, now we will get to the important details.

 Most people get alarmed when they hear banging noises in their pipes but find it difficult to believe they have a problem when everything sounds normal. People don’t hesitate to spend money to make their pipes quiet but, if there are no shock-absorbers (water hammer arresters) on the clothes washer shut-off valves, there is a water hammer each time the washing-machine solenoid (fill valves) stop water flow (whether you hear it or not).
If you can imagine how your elbow would feel if you jabbed a steel rod straight into a brick wall, you might understand the hammering effect that takes place when a valve closes quickly. [Note: Electric solenoid valves on clothes washers, dishwashers and ice makers close very quickly.]

Water hammering and added stress can contribute to premature failure even if your home has normal water pressure. Fill valves on toilets (balcocks), faucets, solenoid valves, pressure reducer valves, and other water control devices are exposed to a very stressful shock each time energy bounces back uncontrolled from a fast closing valve. Shock absorbers (water hammer arresters) provide trapped air that absorbs the bounce back energy flowing back from a fast closing valve.

Capturing bounce back energy also helps to protect supply connections, pipes and water heaters.I think water hammer contributes to premature plastic pipe failure, supply line failure to toilets and faucets and other connection failures. I also think this hammering increases the occurrence of pin hole leaks in copper water pipe. I think water hammering contributes to water heater heat trap problems and could even contribute to premature water heater failure.

If you need more convincing you can buy a pressure gauge with a hose connection and make some observations when your clothes washer solenoid valve closes. Usually it will be easy to see dramatic needle jumps on a pressure gauge even if it is attached on an outside faucet located far from the clothes washer.

Of course, the higher your water pressure is, the more dangerous the water hammering will be and the more it is likely that you will hear it. Some people stop noise by replacing a defective pressure reducer but fail to realize that the useful life of the new pressure reducer will be shortened by the silent-but-still present water hammering.

Much in the same way high blood pressure can be “the silent killer”, high water pressure and/or water hammer can cause major damage.

Homes that rely on a pressure reducer to control high water pressure coming in from municipal water mains must make sure the pressure reducer is working properly(it can also cause banging and other strange noise).

It is important to make sure shock-absorbers are at least installed on the shut off valves for the clothes washer. Even without high water pressure,water hammering can dramatically increase the frequency of plumbing failure and water damage (see the list above).

It is best to have a shock-absorber on every fast closing valve. They are recommended and are available for clothes washers, dish washers and ice makers.

Most home owners can probably install shock-absorbers on clothes washer valves if they are capable of replacing their clothes washer hoses. [Usually hoses should be replaced every five years.] If your dishwasher is replaced, shock-absorbers can usually be easy to add at the same time. The small size of the pipe and the long coil necessary for ice-makers, seems to make shocks less important for ice-makers but one can usually be installed easily.
While I strongly recommend that shocks are at least installed on clothes washers, and preferably on dishwasher supply lines, I want to help people focus on some details.

Extreme care must be taken when screwing hoses on clothes washers. Most washers have soft plastic threads that are very easy to cross thread. Sharp metal threads on a hose will cut across plastic threads and ruin the plastic connection if not screwed on properly. Do not rush. Take the time to watch closely as you gently screw hose threads on to to plastic threads at the back of the clothes washing machine. I usually recommend making hose connections as tight as possible with your fingers (hand tight) and then only 1/4 to 1/2 a turn tighter. As with every plumbing connection, careful testing for even the smallest leak with a dry finger is very important.

Another detail to focus on concerns the attachment of the shock-absorbers. Some clothes washers have very little space for the hoses and for the shocks. You should see how the particular shocks you want to install will fit and if they will be subjected to damage from an out of balance dancing clothes washer.

I like the”Sioux Chief” brand water hammer arresters (shock absorbers) with 3/4″ female swivel hose thread by 3/4″ male hose thread the best only if they fit in the space at the shut off valves (behind the clothes washer) safely. Sioux Chief is not the only maker of easy hose connection type shocks. If the Sioux Chief will not fit properly, you should consider those made by other manufactures.

I like the stainless steel type washing machine hoses best. Some are only rated to be safe for five years, some are rated to be safe for ten years or more. Frequently hoses that have a sharp turn fitting (elbow) built in are desirable, depending on the available space you have. Some hoses have what is promoted as a flood protection feature. I am not sure if I like or dislike the hoses with the “flood protection” feature. I have seen “flood protection” type hoses that stopped flow unnecessarily when I just turned the water main on and off. To reactivate, I had to disconnect and reattach the hose. The “flood protection” type hoses may or may not be improved and they may or may not provide flood protection.

I will write more about important things that make your home safer when I find the time.

I will try to provide details concerning how important a thermal expansion tank is when I find the time. Right now I just want to say that if you have a pressure reducer, you should have a thermal expansion tank. Usually if you have a thermal expansion tank the tank will be very close to the water heater. If you have a pressure reducer it will usually be very close to your main water shutoff valve in your home.

When cold water is heated it expands (gets bigger). A thermal expansion tank provides a place for expanding water to go. If there is no place for expanding water to go, a dramatic increase in water pressure creates dangerously high pressure.

Much like water hammer stress frequently causes premature failure (see the many at-risk items I mentioned above)uncontrolled thermal expansion is dangerous.

Thankfully, now most plumbing codes require the installation of a thermal expansion tank if the home doesn’t have one and the water heater is being replaced in a home that has a pressure reducer.

Now you have plenty to think about-but-please just focus on the shock absorbers for now. If you have any experience at replacing washing machine hoses and you read my details that I provided, I think you should be able to replace the hoses and install the shocks. If you have to buy a new machine and others will be installing a new machine, you should make sure you purchase two shocks and have them install them for you.

If you have to replace your dishwasher, you should have the installer add shocks as he hooks up the water supply line.

About the Author


Mike started his plumbing apprenticeship in 1969. He has over forty years experience solving plumbing problems in homes. Mike helps people avoid mistakes. He is the founder and president of Quick Quality Plumbing Inc.. Mike published a book ( and he is the administrator for the web site (