Rattling Water Heater

Oh Great Plumbing Sages:

My mom's water heater has developed a rattle. The rattle appears to be coming from the hot water outlet. Of course, it only makes this noise when water is flowing. The water heater is plumbed with galvanized pipe and there are two unions just above the hot water outlet. Could one of these unions be making the noise? Help, please!

Don

Some few years ago, they were using ball-check type heat trap nipples. They had a habit of making a clicking noise. Maybe just replaceing the nipple will fix it.

heater.

Turn off the water, disconnect the hot water pipe, and turn on the water. The heat trap ball bearing should pop out.

OK, once the heat trap ball bearing pops out, what do I do with it? Should it be replaced? What in the world is a "heat trap ball bearing"? Never heard of such a thing. Thanks!

Once it pops out toss it over your shoulder for good luck and hook the water heater back up without it!

The ball is what was rattling! Heat Traps are used to stop convection loss... Not a big deal to worry about.