After draining my hot water heater to clean out any gunk that might have settled, I closed the spigot. However, it wouldn't completely close. I tightened the nut on the valve gingerly so as not to overtighten and strip the threads. That seemed to work. A glass jar under the spigot remains dry every time I check it.

However, if I cover the spigot with a plastic screw cap to which "plumber's goop" has been worked into the threads, after a few days, there will be about 1/4 to 1/3 of a capful of water. Why does closing off the spigot cause a leak when there doesn't seem to be one without closing it off.

I did notice this on my outdoor faucet - when I took off the cap I use there, some water is present. But I don't see any drops coming out of the spigot (though I don't keep a jar under the outside spigot to check for leaks.

There are 3 places that a spigot can leak.

1. Where it screws into heater. Wrap thread with teflon tape.

2. At the packing nut. Tighten nut while holding spigot build with a wrench.

3. At the spout. Replace washer or replace spigot.

Chuck

I believe you are saying that if you place a cap on the drain spigot of your water heater, that after a couple of days you find a very small amount of water in the cap.

If that is correct, don't worry about it. Only means you have a very, very, very small leak. The reason for using the cap is because you can't get the valve to stop leaking.