Water hammer...fact or fiction?

[Richard]

What is water hammer?
What causes water hammer?
Can it be designed out?
Can it be managed if not designed out?


Reasons I ask: Went to local plumbing store (several times). One of the guys upon finding out that I'm going from 3/4" copper to 1/2" shutoff valves for my shower, told me that the sudden change in sizes of pipe help cause hammering. (I have heard it before but NEVER in my house yet)

I hadn't thought of it happening to me, I always thought it was in older homes (my experience).

Another time I was there, I asked a different person and he said it was because of AIR in the system, and it had nothing to do with sizes of pipe used ( /forums/images/graemlins/confused.gif )

Clearly they're not on the same page ! /forums/images/graemlins/crazy.gif

Currently, I don't have any waterhammer effect in my home. I don't want to cause it in the shower I'm building. I'd like to take any reasonable precautions to eliminate it and my walls are currently still wide open (much to my wifes chagrin /forums/images/graemlins/tongue.gif)

Should I just add a 10" stub that is T'd off vertically so it's above the waterline? A website I found said if you do that, the air will soon be disolved into the water and it will be rendered useless (besides, isn't that perhaps the same air in the system that one guy said CAUSED it?)


What say the experts?

 

[Egon]

Yes water hammer is for real.

It may be caused by a sudden stoppage, change or change of state in fluid flow.

Yes systems can be designed to minimize it.

And yes, it can cause considerable damage. And yes it can be very noisy.

Egon /forums/images/graemlins/grin.gif

 

[EddieWalker]

Just about every home built has 3/4 supply lines that reduce to half inch. Aint nothing your doing going to cause any problems.

Sounds like somebody was either having fun with you or he's one of those know everything types that's never done any actual work.

I ran a 1 1/2 inch line into my home and have it teed and reduce down to 1/2 inch through out the entire home.

Eddie

 

[Shimon]

If you feel like reading, here is a good page about it: water hammer

 

[duber34]

That was a very good read Shimon. Thanks for the link.

Regards,
Duber

 

[JSUnlimited]

Rich,

Water hammer happens do to the sudden stop of the flow of water. This happens no matter what, pipes, hoses, etc., or combination of sizes of said containers. Usually the problem is the type of valve or device using to stop the flow of water. For example, a solenoid operated valve on a laundry washer opens and closes suddenly d/t electrical automation. Whereas a manual operated valve on a garden hose fixture slowly opens and closes (unless somone uses a 1/4 turn gas shut-off type valve.)
In the fire service, we have relief valves on the pumps mounted on the trucks. Usually manually set, however on the newer trucks, it's computerized. When water is flowing and then suddenly stopped, the relief valve opens and vents the excess pressure out under the truck. Imagine flowing 1500 to 2000 GPM of water and suddenly stopping it. Sort of like a Mack-Truck hitting a brick wall. Somewhere....something will give......usually the weakest link such as the firehose. However sometimes it the pump housing or couplers. Either way for a firefighter it's outright dangerous, even life threatening if you are depending on that hoseline. For a homeowner and plumbing, it's BAD.....and expensive if a pipe or plumbing appliance fails.

In terms of reducing pipe sizes, it's done all the time. Stopping the flow of water is what's important. I'm no plumber so I hope this helps. /forums/images/graemlins/confused.gif

 

[PineRidge]

We had water hammer in an apartment where we lived. Every time the clothes washer water solenoid would close BAM! I picked up a inexpensive set of hammer arresters at Home Depot that screwed on each water line at the washer and that immediately took care of the problem.

 

[Soundguy]

I've seen 'arrestors' that "T" off from a line then terminate.. suposedly they are a cushoning device, built inline inthe copepr extension pipe.. that has some give. ( never seen inside one.. just theorizing on how they work.. )

Soundguy

 

[Cliff_Johns]

</font><font color="blue" class="small">( I've seen 'arrestors' that "T" off from a line then terminate.. suposedly they are a cushoning device, built inline inthe copepr extension pipe.. that has some give. ( never seen inside one.. just theorizing on how they work.. )

Soundguy )</font>

Guess I always thought those little Ts in the pipe were just trapped air. Since air compresses (and water doesn't), it acts as a shock absorber for the hammer. Can't say as I know one way or t'other, but that's what I always thought.

Cliff

 

[PineRidge]

SoundGuy here's what most of them look like on the inside. inside arrestors


The mini's shown lower on the page are exactly what I added to the clothes washer (they work).