James,
My first Beaver was a 1993 Patriot and the fresh water tank drain was just like the one described by Ed. A word of caution though, if the water is coming out of the tank housing by the insulation at the drain valve, it may not be the drain valve leaking. The supply line to the tank enters the tank near the LF lower corner, and that is were the fresh water tank leak on my 93 was even though the water dripped out of tank housing by the drain valve.
The supply line fitting that was plastic welded to the tank cracked, and I had to remove the tank and take it to a plastic fabrication shop to have a new fitting plastic welded to the tank. The shop just ground off the old fitting, then they welded a one inch thick block of polyethylene to the tank and drilled and tapped it for the supply line fitting.
Gerald