www.paushe.com: summerizing

First flush out the antifreeze by connecting a hose to the city water and then run all taps (shower, toilet, bathroom sink, kitchen sink, outside) until clear; then turn off the water
Turn two petcocks at pump to summer position
Fill freshwater tank, including 1/2 cup of bleach for 30 gallons of water, run 12V pump to push solution to kitchen and bathroom sinks, and let sit for three hours (make sure smell of bleach in the water before turning off taps).
After three hours, turn on pump and run kitchen and bathroom taps to drain freshwater tank, refill tank, drain again
Turn three petcocks at hot water tank to summer position
Turn on city water to fill the hot water tank and flush the system until no bleach scent
turn on gas and test hot water tank heater operation

EXTERIOR

Install group 24 battery (install the Group 27 or stow it in bike area as a 2nd, if dry camping)
Unroll awning and check
Check exterior lights (jump 11 & 1 pins in Bargman connector with a fuse), including dump valve light and step light
Remove winter covers from fridge and hot water vents
Remove tire covers and store in garage for use when parked in driveway (UV protection)
Air conditioner: remove external winter cover, clean filter, test; check screws that hold shroud to ceiling
Front trunk: return anything taken out for winter (usually cordless drill and torque wrench only)
Wash and wax (including washing roof)
Lube stabilizers
Lube locks and hinges

Tires - check air pressure, torque (including spare)

Hensley Arrow - uncover, grease spring bars, ball, torque nuts check all bolts

Hook up truck and test all electrical connectivity

Open a victory beer