Water hammer - air in pipes

[jug]

Hi all
When I turn on the basement washroom hot water....the pipes bang and rattle like a jack hammer....I drained the system and it goes away for a days and comes back. I friend ( plumber ) told me to install a water hammer arrestor on the washer and dish washer and that would get rid of it but I went home depot told the guy about the issue I have and he said the arrestor won't help???
Any advice.
Thank you!!!

 

[Terry]

If it's the hot side of the lav faucet, I would first open up the shutoff all the way on the hot side.
It may be a loose and faulty rubber washer that is fluttering when the water goes by it. Sometimes opening the shutoff all the way is all that is needed.
You can also replace the shutoff if you determine that it's gone bad.

Normally with air chambers in a home, you can replenish by draining down and refilling. The water chambers will waterlog again.
Hammer arrestors are mechanical, so they don't waterlog.
We install them for dishwashers, washers and ice makers. Plumbers know that, and so does your friend.

 

[Sponsor]

 

[hj]

An arrestor will do NOTHING if the noise is caused by opening the faucet. That usually indicates a faucet in need of repair. It is also NOT "air", unless you have a compressor connected to your water pipe.

 

[LLigetfa]

Normally with air chambers in a home, you can replenish by draining down and refilling. The water chambers will waterlog again...

hj claims that waterlogged air chambers cannot be drained and replenished. That may or may not be the case depending on where and how they were installed. When I did my plumbing, I situated them so that any air that could be in the lines might rise up into the chambers. hj also stated that you need a compressor to get air in the lines, but on the hot side, small amounts of air can separate from the water due to heating. You can see that in action when you start to heat a pot of water on the stove.

If it was air, then it would likely spit out on first use and quickly diminish. Most likely it is not air but rather vibrations from a loose stem or washer. If there are waterlogged air chambers, replenishing them with a bit of air could change the harmonics enough to stop the vibrations but as Terry said, they will quickly waterlog again. Mechanical arrestors have a piston and O-ring seal to keep the air precharge separate from the water.

 

[Reach4]

Yes, but jug said "I drained the system and it goes away for a days and comes back." If you open high and low faucets, the chambers should drain and not fill up in a few days or a few weeks. I did not follow the bit about the air compressor either.

That plus the fact that jug said that the noise happens when the faucet is opened indicates it is not water hammer, as HJ said. In fact, it could some repeating/continuing/oscillating noise rather than the single sound that water hammer is.

 

[LLigetfa]

If you open high and low faucets, the chambers should drain and not fill up in a few days or a few weeks...

There is no guarantee that they will ever drain completely and so there might be only a small amount of air trapped which quickly gets absorbed. Agreed that it is not classic water hammer but rather an oscillating jackhammer sound.

 

[hj]

Have you ever seen a bottle full of water inverted? SOMETIMES it will drain out, but if the end is under even a small amount of water, it stays in the bottle. An air chamber is a very small column of water and there is seldom enough "pressure" to let the water out and air in through the same small opening.

 

[Craigpump]

Maybe I missed it, but did he say whether he's on city water or private well? If he's on a private well, the system could be getting air bound due to leak between the pump and tank.

 

[Jadnashua]

Water hammer occurs when you abruptly stop a flowing column of water (typically, fast acting valves like solenoid valves used to control things like ice makers, washing machines, etc), the inertia causes it to hit upon the now closed path, and it can literally hammer the pipe up against something, making the sound. On a washing machine hose, you might only see the hose jump (not particularly good for it). A flaky washer or something caught in the water stream can bounce around during flow, and momentarily cause the flow to start and stop, or at least flutter, also making a sound (more often sort of like a machine gun). A classic water hammer is a one time bang when you close a valve fast enough (course, it might rebound and hit something else if it moves far enough). So, depending on what it is, a hammer arrestor might resolve it, but as said, if it happens when OPENING a valve verses closing one, it is more likely something in the water stream itself banging up against an obstruction, affecting the flow than classic water hammer.

 

[Asktom]

Water hammer discussions, air chamber, arrestors etc will not help Jug, that isn't the problem. Do like Terry said and fiddle with the setting on the angle stop, which may or may not fix it. If not, shut off the hot side and pull the stem, the washer is either worn or loose. Take the stem to a decent hardware/plumbing store and get a new washer and seat. If you have a seat wrench, yank the seat and take it with you. If you don't have one, get one while you are at the store. They should be able to determine the seat you need from the stem and you can double check it to be sure it identical when you pull the old one. I would put a bit of pipe dope on the seat's threads, HJ wouldn't. You might get a couple extra washers and a second seat so you will be ready when you need to work on the cold side.