I Just winterized My 335 today and wanted to share a few notes which I hope will help others on the forum as I have been helped in the past:
a) Water Pump: The water pump is located dead center in the bottom of the island, behind the bottom drawer facing the Stove. The drawer can be removed for better access by pressing on 2 SMALL black plastic release levers which can be seen on the inner end of the outer most section of U channel on the drawer slide when the drawer is fully pulled out. Push the ride hand release down and the left hand release up and pull out the drawer.
On the inlet pipe of the water pump there are two pipes attached to a T fiiting: One pipe goes to the fresh water tank and there is a cut off valve which should be turned off to prevent anti-freeze from going into the fresh water tank, The other pipe is connected to nothing and is used to stick into the antifreeze bottle in order to pump anti-freeze into the system. There is also a cut off valve on this pipe, it is normally closed, but when pumping anti- freeze you open it.
b) Water heater: The water heater by pass assembly is located behind the access hatch in the main cargo bay on the back wall - driver side. You must remove the access hatch by removing the screws securing the access hatch. Ther are two cut-off valves in the bypass assembly: one valve cuts off the water into the water heater ( the lower coupling on the tank), this valve is normally open, but is closed when anti- freeze is in the pipes thus preventing antifreeze from entering the water heater, the other valve controls the bypass pipe between the input and output of the water heater. This valve is normally closed, but is opened when anti- freeze is in the pipes.
I believe the actual winterizing process is covered elsewhere and I will not go into details here.
Here's hoping for an early spring so I can get back to the open road.