Replies

1. 
   David_Thomas | Jan 24, 2002 12:27am | #1

   *
   Like a bang that shakes all the pipes in the house? That is "water hammer". It is due to the momentum of all the water suddenly coming to a stop. The momentum gets transferred to the pipes which then move if not secured well.

   The fix: Add air cushions and secure the pipes better.

   Air cushions can be found pre-made in the plumbing aisle. These units are sealed and preferred but a cost maybe $5 each. Or you can site-build unsealed ones. Remove a 90 or two and replace with a tee. Take the extra leg up (so it will trap air) and run it 6 or 12 or 18 inches. More is better. Ideally, choose locations at the end of long, straight runs. The site-built ones eventually water-log. Drain the house plumbing to replace the air in them. Put ones on both the hot and cold runs. If the run from the well is long, consider an air cushion there are well.

   Securing the pipes should be done with an eye to minimizing longitudial movement (along the length of the pipe), not just holding it up against gravity. I often wrap a bit of tar paper or 1/8" closed-cell foam (the stuff used under bottom plates) to pad between the pipe and the pipe strap. It eliminates the metal-on-metal noise when the hot-water pipe expands and lengthen when hot water flows through them.

   Get under the house, if you can, and listen for where the waer hammer is coming from. Just grasping the problem pipes firmly in your hands will reduce the noise and confirm that you are on the right track. Good Luck. -David

1. 
   Wet_Head_Warrior | Jan 24, 2002 12:47am | #2

   *David, did you ever make an air cushion out of a clear tube and watch it? I did. It is my opinion they are worthless. UPC says if used they must have a means to add air. Not knocking you... would like to hear your comments.

1. 
   David_Thomas | Jan 24, 2002 01:21am | #3

   *WHW: I haven't done exactly that, but maybe I will now. I've had sight glasses on process equipment for the purpose of visualizing the liquid height (like the glass tube on a coffee percolator). And sometimes I've constructed little (2-3" high) air-filled head-space chambers for the purpose of detecting contaminants in the water*. Those do bump around when you close the valves quickly. So it seemed like they were acting like little shock absorbers. But smaller diameter transparent tubing would make the dynamics clearly.I've got a precision gauge (5", liquid-filled) on my piping manifold. Interesting to watch the effects of water use and the patterns of city water pressure. In NYC, they can detect commercial breaks during football games and popular shows by the drop in pressure caused by all the flushing.Didn't know that about UPC and air additional. Thanks. Seems easier, IMHO, to drain the piping and refill (one valve, one bucket in the utility room) than to run around under the house with a air compressor hose or bicycle pump.Another "fix" to water hammer is to close valves slowly or install only slow-closing valves. I used only ball-valves in my own house, but then I know how to use them. Your thoughts? * Volatile water contaminants (like benzene, gasoline, TCE, etc.) are much easier to detect in air than in water. So the head-space chamber is to allow a few cubic inches of air to come to equilibrium with the water in question. -David

1. 
   Wet_Head_Warrior | Jan 24, 2002 02:39am | #4

   *Yes, they make great shock absorbers. Just don't last. I use only ball valves too. Anywhere there is a quickacting valve (Delta single handle maybe) I install a Sioux Chief hammer arrester nearby. They are cheap and permanent.Yeah I hear you on the drain down thing... but who wants to do that as often as needed? Or fill it like code implys?Often the expansion tank I install at every water heater takes care of most of the problems. Sioux Chief has one you can install at a supply stop so I always check when job is done and if needed install one at problem location.

1. 
   xJohn_Sprung | Jan 24, 2002 04:19am | #5

   *What I was told the problem is with the unsealed dry risers is that the air in them eventually dissolves into the water, and they fill up and lose their cushioning ability.-- J.S.

2. 
   Wet_Head_Warrior | Jan 24, 2002 04:27am | #6

   *yep

3. 
   David_Thomas | Jan 24, 2002 10:17am | #7

   *Hence the advantage of the sealed units. Which perhaps should be a no-brainer: spend $5 to avoid a periodic maintenance item that goes on forever. But if you're laying pipe, you can always site-build one. Versus running to the hardware store for a couple of sealed units.