1. I forget...
2. The drain is out of sight on the bottom of the tank so...... I forget
3. The drain is hard to reach so......... I forget
4. When I do remember, but because I forgot for so long, the petcock is rusted in place

Since I don't want to wreck a good air compressor, I figured I best come up with a simple inexpensive solution.

Step one was removing this stubborn bugger. Being made of brass, the corners were easy to round off even with the correct sized wrench........so it called for vice grips.

Now that it's out, let's see how much water was in my tank......

Yuck......... at least a quart of dirty rusty smelly "water"

Off to Lowes for a few common plumbing parts. The hole takes a 1/4" NPT thread and I was hoping to get away with galvanized or black pipe but all they had in that size was brass..... a 90 degree male/female, 3" straight pipe and a shut off valve.

A little Teflon pipe thread sealer and we're good to go.

The only thing you have to pay attention to is the handle orientation so that it doesn't hit of interfere with anything.

I need rubber bumpers on that support bracket!