I was winterizing the trailer last weekend (sad but true... summer is over for us
) and using air pressure to blow out the water lines. I gapped out and put the water heater valves in bypass while I still had pressure on the lines.
I was puttering around, ran a bit of antifreeze in the lines etc...I went to drain the water heater about an hour later and as I was removing the anode rod in the heater to drain..I could hear a hiss as I was getting down to the last of the threads...before I knew what was going on...BLAM... It shot the rod out, and six gallons of water in a real hurry, with most of it ending up on me. Thank god I was standing to the side as that rod is about crotch level!
It did a good job of blowing out alot of crud, also I was amazed at how much was chewed off of the anode rod over the summer, as we only used it for about 10 nights this season....next year I am draining the tank after trips.
Also keep in mind there is still alot of water left in the bottom of the water heater, I use a wet & dry vac and a skinny hose to suck up the remaining water. I use the vac also to suck out the traps in the sinks...and replace the water with antifreeze.