Water hammer...fact or fiction?

Soundguy · Apr 10, 2006

( I think you might be interested to know that todays pressure tanks will take care of the water hammer problem.

)

If you have a check valve between your pump and your house ( I do.. I think it is code in FLA now. ) then the hammer can still occur in the house. I have the arrestors installed at my WH.

Soundguy

Soundguy · Apr 10, 2006

( 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 )

I don't think it would be a simple electronics upgrade.. but rather a different valve. Most all electric water valves I know of are solenoid or diaprahm dump valves.. they are either open or closed.. no inbetween. What you are asking about would have to be some kind of valve that orificed down.. perhaps with a worm gear setup.. would need a sensor for full open and full closed.. either motor current sensor.. or adjustable stops... I think that woud way overtick the plumbing ( no pun intended).. Probably at best.. they could install an integral hammer arrestor to the input of the water line, and that would be easier and cheaper than the worm drive orificed water valve..

Soundguy

PILOON · Apr 10, 2006

( ( I think you might be interested to know that todays pressure tanks will take care of the water hammer problem.

)

If you have a check valve between your pump and your house ( I do.. I think it is code in FLA now. ) then the hammer can still occur in the house. I have the arrestors installed at my WH.

Soundguy )

Thanks for the answer, Soundguy.
We don't use checkvalves between pump and house here.

We do often place a check valve near the pump on the intake (suction) line however on jet pump installations to help keep the intakes primed as the smallest piece of foreign matter can let the foot valve deprime the intake. (Naturally not needed with the artesian type well pumps.)
Also many folks have heat tracing wires installed as frost here goes to about 4ft. A deprimed line lets some heat tracers overheat and blow. And those tracers are costly to replace.
Our problem is the land is so rocky that often we can't dig deeply enough to avoid frost line.
But the scenery is beautiful and worth the inconveniences.

PILOON · Apr 10, 2006

Re adding anti hammer to a washer;

I have been told that any product that is manufactured costs 10% in raw materials of the retail price.
Meaning that an 'anti hammer' solution incorporated in a washer would raise the retail price by about $75.00.
That is probably why they dont do it.

But a valid suggestion.

In production costing they always go to the engineered line and never over, to the point of special production runs of a non standered resistor to save $$. Or maybe a 3.5 amp diode when a 5 amp is an industry standard.
Was told GM went to the side battery posts due to the fact that it costed about $1.00 less per vehicle (cost of lead, weight (shipping and MPG).
In other words,'Good enough' or 'meets the specs'

Soundguy · Apr 10, 2006

( In production costing they always go to the engineered line and never over, .....
In other words,'Good enough' or 'meets the specs' )

I surely believe that. The last 2 companies I've worked for have that mentality when it comes to product engineering.

We have actually even taken a concept or 'off the shelf' product, seen how far it exceeds job specs.. and then de-engineer it and come up with a product that save a half cent over the original, and is way de-rated, and use that instead.... I'm sure ( I would.. ) the consumer would pay the other half cent to get the extra ratings.. but then.. what do I know.. I'm in the eng dept... /forums/images/graemlins/shocked.gif

Soundguy

fenneran · Apr 10, 2006

We had this in our office building last year. We all heard a big "Boom" and figured it was someone in the next office screwing around. Turns out that it was a water main breaking in a closet in our other building. When someone noticed water seeping out the door, and they opened it to investigate, a room full of water and a six-inch main line went streaming into our call center. Within minutes there was 4 inches of water throughout the building. Turned out the city guys were up the street and closed or opened something a little too quickly and our building was at the end of the line. It was a mess.

midlf · Apr 11, 2006

When our washer cuts off the water supply it appears to take a 1/2 second or so for the valve to shut. No noise and no hose movement. So I wonder if the snap off type of valve has been superseded by a slower acting one.

GE about 3 yrs old.

Chuck52 · Apr 12, 2006

I've got one of those hot water circulating systems in my newly added master bath because it is a long run from the water heater. This pump is on a timer, and before we normally get up in the morning it starts running the hot water through the cold water line until it gets to a set temperature at the pump. Nice to get a hot shower quickly in the morning, and reduces the wasted water. However, there is a slight hammer when the solenoid shuts off, so I bought one of the small arrestors to install under the bathroom sink where the circulator is. I haven't installed it yet, and now I'm wondering if I really need to put it under the sink, or would it do the job anywhere else in that line......say somewhere more convenient and easy to work at? In other words, how close to the source of the hammer effect need it be? The instructions say "as close as possible" or something of the kind.

Chuck

PineRidge · Apr 12, 2006

Chuck I believe what you are referring to is a rapid-delivery hot water kit . I installed one here at our place after the builder told me that it really wasn't necessary, (right!) When the pump is running its almost instant hot water at any tap in the house.

I think your arrestor will work best if you can get it as near the offending culprit as possible.

JD4610 · Apr 12, 2006

I usually try to explain water hammer to people like this: Imagine that your water pipes are train tracks and the water is a train. If that train is running down the tracks, and you slowly close the faucet, the train comes to a gradual stop and no harm is done. However, if you quickly slam the faucet shut the 'locomotive' at the head of the train stops more or less instantly, and all of the 'cars' following plow into it. This causes a huge spike in pressure at the closing valve that actually swells the pipes momentarily, followed by a backwards-progressing shock wave of water that slowly dissipates throughout the pipe network. This pressure wave is what can cause a noise at a location far away from the faucet or valve being shut and is affected by the size and length of each pipe, how far from the valve it is, and the "springiness" of the pipe itself.

The water hammer arrestors work by giving the water a temporary detour when the valve shuts, and absorbs the pressure like an accumulator in a hydraulic system. They need to be installed as close to the valve or faucet as possible for maximum effectiveness, and are a code requirement in many jurisdictions.

When I designed and installed the water system in our house three years ago I used water hammer arrestors at the dishwasher and washer hookups and no air traps at all. It never made a peep no matter how fast you closed any of the faucets, until a few weeks ago when we installed a new LG brand washer. I now get a slight knock occasionally from a pipe near the second floor bath that had never been there before and only happens when the washer valve closes. Back to the drawing board, I guess. /forums/images/graemlins/blush.gif Jay