Water hammer?

'Hot's on the left, cold's on the right, E36 M3 don't flow uphill, payday's Friday and the boss is a sumbitch'. See, I'm qualified to be a plumber. But water hammer? I dunno.

chez Curmudgeon was built in 1979 and has a combination of copper and the newer plastic pipe, I have had no problems with water hammer until the last day or so and it seems to be confined only to one faucet in the master bath. I understand what it is, but WTF would make it start all of a sudden? AFAIK there is no accumulator etc in the system, or at least if there is I can't find it.

What sayeth the hive mind?

Water hammer is bad. It destroys plumbing. And firetrucks.

You should have a bladder tank somewhere, maybe two. If the bladder has deflated or failed, you will have water hammer.

Do you have a well?

I'm on city water, no well. It's weird how it started all of a sudden and seems to be confined to one faucet. I did notice something else this morning: after I ran the shower the faucet quit doing the water hammer.

Do you have a thermal expansion tank?

Clicked on this hoping for some awesome new tool.
Disappointed.

near all my faucet copper lines - there is a tee with an extra copper leg capped off. I thought this was the general design to help with water hammer.

I'll try to do better next time.

I didn't see an expansion tank anywhere under the house, I may need to add one. I did see something about adding that 'leg' to help with this, but if they are present they are behind the drywall.

It might be as simple as a loose pipe clamp.

Some of the water hammer arrestors are just a place that collects air in the piping. If that void becomes water logged, you loose the air cushion. One simple thing to do would to drain down your system.

But first, try messing with your shut off valves below the faucet. If they are not open all the way, open them up and vice versa.

If you have any valves on the mains feeding water to the area, make sure they're open all the way.

Chances are your local (to the faucet) water hammer arrestor popped it's little air pocket.

If you want some product names for water hammer arrestors: Watts or Zurn/Wilkins A design guide: http://content.zurn.com/pages/technicalinformation/Arrestor/WH%20Combined.pdf

A cheap band-aid fix is to turn the main water off in the house, then open the spigots to drain everything down to the lowest outlet. Close them and turn the wataer back on.

Many times, this fixes the problem. It simply lets air back in to act as a cushion, stopping the water hammer effect.

Right, there's air in the system. Drain it like Fox said and it may go away. Somewhere, somehow in the last few days air has been introduced into the system.

Think "Bleeding Brakes".

Think opposite The air was absorbed into the water. The air compresses when shock waves happen in the water. Water doesn't compress so much = water hammer.

I am an engineer at a company where very smart people have been flowing fluids through pipes for decades.

Water hammer sucks, is very destructive, very hard to predict, and harder to fix.

Good luck. Something as easy as an increase or decrease in input pressure could cause a system to suddenly experience water hammer.

Huh. On the oil tankers, we would get a water hammer all the time and never worried about it. A bit different though, as it wasn't air in a water line, but water in a steam line. You put steam through pipes to heat the oil cargo sometimes, and the water would run down the steam line on deck and slam into an elbow. Far as I know, it never broke the steam line.

Water hammer isn't air in the line, it's lack of air. The air acts as a cushion, without it you get hammering.

This is a decent image of a home made water hammer control. Just a pipe on each side (hot and cold). As long as there is air in there, it dampens the water motion and eliminates the hammer.

Time passes, and the air gets absorbed into the water. Then hammering starts.

The fix is what I described. Turn the water off and drain the lines. That lets air back in. Turn the water on, and the air gets trapped in those lines again. It only takes a few minutes to do it.

Water hammer is now gone. It will come back in time. Just repeat the drain down.

Fancy water hammer fittings are just like this picture, but have a rubber diaphram to keep the air from migrating into the water.

This is the exact same problem as wells and their pressure tanks.

Water hammer has nothing to do with air. (Air in water is cavitation, different animal altogether.) Water hammer is a hydraulic shock, and can come from an abrupt change in direction, a sudden pressure surge or pressure change like closing a valve. The shock wave travels back and forth through the lines and makes noise. Hammer Arrestors are simply a shock absorber, using a piston or diaphragm, to absorb the shock wave. I have not seen one that uses an air pocket, but it sounds like they exist and if the pocket was lost, then it would explain why it no longer works. I would recommend finding the source of the hammer and stopping it however. Arrestors are for an occasional shock when closing a valve, not for a sustained problem.

So why did it start all of the sudden? Most likely a pressure change somewhere. That faucet was just below the threshold for water hammer, but pressure has increased locally and now it is making noise. Most likely, calcium buildup inside the faucet reduced the ID of the pipe or orifices in the faucet. Reduced ID means less flow and greater pressure. Greater pressure means water hammer. Take the faucet apart, change O-Rings, and clean out all gunk buildup.

Another option is that it always hammered, but the pipe was secured tightly and you never heard it. A clamp may have shaken loose somewhere. Still, fix the cause. Is your main pressure regulator going bad and allowing more pressure to the system? This usually means water hammer at one faucet, which spreads to others, then everything starts to leak. A pressure gauge attached to the slop sink will tell you where you are set.

foxtrapper wrote: Water hammer isn't air in the line, it's lack of air. The air acts as a cushion, without it you get hammering.

I am pretty sure this is wrong. It's about fluid flow, air presence notwithstanding.

We develeoped water hammer over the years, but it got a lot worse when we bought a new washing machine. We had known for a while that we have high water pressure in our neighborhood and the HOA advised everyone to install a pressure reducer. We did and the hammering went away. I'm not sure if we have the small air pockets, but I don't think we have one of the larger tanks. If it every comes back, I'll do the drain down thingie.

Fast acting valves can lead to water hammer. Washing machines tend to have fast acting valves...

RossD wrote: Fast acting valves can lead to water hammer. Washing machines tend to have fast acting valves...

I have also heard this in industry. We slew valves open for this very reason.

A regulator at the inlet may be the right fix.

Or a shut off valve with an arrestor built in like this laundry outlet box:

If you do work with the state of wisconsin, you have to install arrestors at fast acting valves on domestic piping and specifically at washing machines; it's in their specs.

If it started all of a sudden in one faucet, start at that faucet. There could be something in the aerator or stuck inside the valve body. Water hammer is caused anytime you stop the flow of water suddenly. The hammer you hear is the vibrations of the pipe smacking up against the framing. If all else fails, install a pressure tank at the meter.

Shotgun. Be sure to fire the warning shots first.

I knew I could count on this bunch!

AFAIK there's been no change in the water pressure, but the City of Columbia is not known for covering anything with their customers. Well, except for rate increases. Since it seems to be confined to one faucet, I'll check it out thoroughly first.