Re: "machine gun" water pipes
Posted by Robert on April 24, 1999 at 02:12:39:
In response to Re: "machine gun" water pipes
: Sometimes it just happens. Most often, however, it happens when any spigot in the house is turned on. The pipes vibrate and sound like a machine gun. It lasts until the spigot is turned full on, or, when it just happens, the "machine gun" sound lasts from 5 to 10 seconds and then stops. What's going on and how can I eliminate the problem. Thanks.

The noise you are hearing I beleive is what is called water hammer. What is happening is that when you turn the water fauset on, the water, which is at a stand still suddenly begins to move but then is regulated by the fauset, and this causes an osilation to occur or in other words a shock wave is sent back the other way through the pipe. It's kind of like having a room full of people and when you open the door they all move to the door at once. Water weighs about 8lbs/gal. so if you added all the water up between your fauset and your meter it would add up to alot of weight, so when it is suddenly stoped or slowed down enough, it makes a loud bang each time it occilates because water doesn't compress very much if at all. Most plumbing systems have one or more what I beleive is called a stand pipe. This is a small piece of pipe in the water line somewhere, usually about 3-4 inches long that sticks straight up and is capped off as if it were going to be used for something but wasn't. This traps air in the line and creates a cushion for the water bounce on thus eliminating the bang. In some older plumbing systems it was designed to hold a little air some where in the system for this purpose. The problem is that eventually the air is worked out of the system until there is not enough air to cushion the water anymore. The way to fix it is easy! Just shut the main water valve off, and drain all your water pipes by opening all of your water fausets. When you can get no more water out of the pipes, close all the water fausets and turn the main water valve back on. One at a time, starting at the lowest fauset in the house bleed the air in the pipes out by turning the fauset on until no more air comes out. Then do the same for all the other fausets. This sould get rid of the noise.

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