Water hammer...fact or fiction?

[Regal]

<font color="blue">Somewhere....something will give......usually the weakest link such as the fire hose. However sometimes it the pump housing or couplers. Either way for a firefighter it's outright dangerous, </font>
Richard; The example that Mega Me gives of 1500 to 2000 GMP flow is very good. For instance if two lines are flowing and one person quickly shuts his nozzle off, the pressure is directed to the other open nozzle. Without some sort of pressure relief built in, the extra surge could be quite a surprise to the person on the other line. We are not really comparing apples to apples here though. 1500 GPM at 100+ PSI vs what? 20GPM at 60 PSI ? Even though, at 8 lbs per gallon, anytime you abruptly stop the flow you could cause water hammer.
You are installing a shower? IMO I wouldn't be concerned with hammer there because you are manually shutting it off, probably not too fast. As someone else pointed out, a washing machine solenoid valve does shut off instantly. If you don't have a hammer problem there then I don't think you will create one with your shower.

 

[rebuilder]

Once pushed about 60 feet of water line right out of the ground with a 1000 gpm fire truck. Made for one very unhappy fire chief. (It was at a drill!!)

 

[turnkey4099]

Just started reading the thread so excuse me if someone else has already answered.

Water hammer is caused by a stream of water suddenly being forced to stop, e.g., rapidly shutting off a valve. A hammer can cause real damage right up to breaking piple joints.

Yes it can be designed out but the 'pipe' stub is not the way to go. The guy that said the air will disappear is correct.

Correct way is with a surge tank. That is a small tank that has a bladder in it to keep the air and water separate. It acts as a 'spring' to absorb the shock. Best is to position it near he end of a run. They are not high budget items so in doubt, use more than one.

The guy who said air in line causes it is, to put it mildly, full of it.

Harry K

 

[Soundguy]

The water hammer arrestors that I and another poster spoke of use a gas cushion and a piston to seperate the water from the gas...

Soundguy

 

[turnkey4099]

Yes they do. They are also a bit smaller and easier to install.

Harry K

 

[PILOON]

Since many TBN's have wells hence use pumps, I think you might be interested to know that todays pressure tanks will take care of the water hammer problem.

The most commonly used tanks have a 'bladder' setup or baloon inside of the tank to equalize pressure.
The trapped air in the bladder takes care of the hammering as it becomes the system shock absorber.

 

[PineRidge]

Piloon that may be the case in some or most installations but I can tell you from first hand experience that we have a well here with a bladder in the water tank (air charged tank) and still got water hammer at the washing machine, hence the water hammer arresters were installed at the washer itself. We have no noise problems at this point since the arresters were installed. No, I don't own stock in the company either. /forums/images/graemlins/cool.gif

 

[PILOON]

PineRidge
Come to think of it, my washer kinda clunks and it is about 5" from the tank.
As someone else mentioned, solenoid valve make for a sharper more sudden shut off.
Always figured that I was hearing the clank of the volve rather than a hammer.
On the other hand none of the pump fitted houses that I know have any hammering and most were built by DIY's that for sure never installed anti hammer devices.

In my house only the washer makes a hammering and it also did it when it was in the city.

I know that just about any tap in a non hammer protected plumbing can cause hammer and was common in older homes that had higher pressures.

Maybe I'll order one of those devices.

 

[RobertN]

I have heard of water mains breaking 1/4 mile away from where a hydrant is closed to fast, or a valve is closed to fast.

I have heard water hammer in a pump. I had heard it in a home water line, but never on an engine. When it happened, it had a very metallic sound to it. The guy was lucky he didn't blow the pump; fortunatley he only flowing 100gpm or so... All of us on the crew knew immediately what it was though...

Water hammer can be an issue in irrigation lines. If the pipe has a weak glue joint, a fast opening irrigation valve can make it pop.

 

[PineRidge]

Being the kind of guy that always asks "what if" I have to wonder what tiny PC board the manufacturers could add to a clothes washer. The PC board could enable soft stop of the water solenoid valves similar to the way a dome light on a new car slowly times off after you get in the vehicle. I would think washing machines cause the majority of hammer and this idea might just eliminate the need for arresters within the home altogether. Somebody call Maytag, quick!