Water hammer and what is the cause?

Question

I have seriously rough case case of water hammer in the lower level bathroom. It only occurs when the hot water is turned "on" by itself. If cold and and hot are turned on simutaneously or if hot is turned on after cold, no problem. If hot is turned on by itself, man, it's like a train is going by right outside my door. Wife is buggin. I have no peace. Can you help a brother out?

If this is just a washer job, I'll try to tackle it myself. If I need hammer arrestors and the like, it's a plumbers job. Perhaps I need need to re-establish flow (tried b4;failed, perhaps not done right). My wife called a repair man who suggested a new hot water heater. My house is eight years old so you see what kind of criminals I'm having to deal with. I really need to be able to do this myself. YA team, can you help?

Answer 1

As one of the other answers suggested, if this is happening when you turn the water on, it is not classic water hammer.

Water hammer - in the traditional sense - is caused when you have water flowing and shut it off very quickly. Why? Water has a density of approximately 8 pounds per gallon. When you shut the water off quickly, the decelleration is very quick which causes a spike in force (and also pressure). This force/pressure spike is what causes the pipes to make the sound -- not much different than if you were literally hitting them with a hammer (only it's the mass of the water inside the pipe). A water hammer arrestor is simply a tube in which a pocket of air is trapped which absorbes the pressure spike and dissipates the energy from shutting the water off quickly. You can buy them pre-made, or you can make your own if you know how to sweat fittings.

As to what is happening in your situation - I agree with the other poster that this is probably the result of a ballance valve on your faucet not functioning properly. What I suspect is happening is that because there is no cold water, the ballance valve is cycling on and off quickly trying to ballance the flow of hot with the non-existant flow of cold. This on-off-on-off cycle is probably happening as a natural, resonant frequency in your waterline.

Ways to fix it:

The easiest way would be to replace the faucet.

Does this happen only if you turn the hot water on quickly, or does it happen even if you slowly turn just the hot water on?

If it happens regardless of how quickly you turn on the hot water, then I'm more inclined to think this is the valve. If it doesn't happen if you turn on the hot water slowly, then you may (50/50 shot here...)be able to fix it with a water hammer arrestor.

Is it your water heater - no, that guy was looking to make a buck off of you. Wish I could help more. Good luck!

Answer 2

Water hammer is a pressure surge resulting when a fluid in motion is forced to stop or change direction suddenly. It occurs when a valve is closed suddenly and a pressure wave propagates in the pipe.

Water hammer on a water line will commonly result in very high pressure  spikes. These spikes are not just at the valve, but they reverberate backwards from the valve throughout the whole system, rattling and shaking pipes, until it is absorbed. If you don't fix it, it can mess up your water heater, washing machines hoses, pipe, fittings, and more.

There are only two ways I know of to get the air out; push it out by increasing the water velocity (speed), or open the pipe and release the air.

To push the air out you need to temporarily increase the water velocity to the point the water "sweeps" out the air bubbles. To do this turn on all the faucets in the house and then flush all the toilets. Again, give it a few minutes to push that air out. If you know where the water supply comes into your house turn off the faucets starting with the one closest to the water supply entry point, then close them one at a time moving away from the entry point. As you come to a toilet when you are moving through the house turning off faucets, flush it again, then wait two minutes before closing the next faucet. Don't forget the faucets on the outside of the house!

Good luck

Answer 3

I betcha it's a loose washer.

Answer 4

The water hammer could be caused by a washers fludder in the faucet or the angle stop under the sink. Try this first close off the hot water angle stop and open it a little bit to see if this solves the problem, you can adjust the angle stop to stop the problem and this will only take a few minutes to see if it works. No tools needed for this fix!

Answer 5

If the sound occurs when the hot is on then you have a bad valve in the faucet. Depending on the style of the faucet it may be easier just to replace the faucet itself rather than figuring what part is bad. I suspect the hot valve has an internal restriction and some type of balancing valve that has to do with the hammer. It is fairly easy to change a faucet with just a minimum of tools. Good luck!

Answer 6

While any of the above could be right, try this first:

Shut off your main water supply and then turn on all your faucets, showers tubs and flush your toilets. Next turn everything back off and turn on your main water.

When you use your faucets, etc some air will blast out ...this is normal.  

Answer 7

Water hammer noise is usually when you turn the water OFF: the momentum of the flowing water causes the pipes to go high pressure for a moment, making the clanging racket in the pipes.

A water hammer is nothing more than a trapped air space to absorb the water's momentum. Usually, there is one each on the washer hot and cold lines, hidden in the wall. You'd have to check and see if they're present, if not you might be able to find some s***w-on types that go between the washer and the valves.

If you plan to put a water hammer on the heater it's easy if you have copper pipes: just cut, put in the T and sweat it in. If they're steel threaded, those are a pain... need a threader, etc.

Knowing it's an easy job then it should be cheap for a plumber to do it. The one trying to sell you a heater... well, maybe yours is old, but it isn't the problem, is it?

EDIT: the wonky faucet is a possibility. That's an easy thing to fix - get a different faucet. Even if you 'fix' this one it'll probably just do the same thing again down the road.