As per the message since it was post over 120 days it says to start a new thread..... So where is the petcock located on the muffler.?
Forward side, port corner area, just above the seam of the muffler. When you open the cabinet door under the head sink, the muffler is the square white fiberglass looking box with a hose coming into the top of it from the wet exhaust pipe. Its a standard automotive brass radiator petcock available at any auto parts store.
kev : You can access that petcock from the head as it's under the sink.
It's the brass looking thing on the right front near the bottom of the muffler.
thanks..... will look for it