How they plumbed your water heater is model dependent. They all should have bypass valves or when you winterize you will use an additional 6 to 10 gallons of RV anti-freeze to fill the HW heater.
There is a one valve type that uses a "T" type valve and a check valve in the hot water out port in the water heater, and a 3 valve system that uses no check valves. There have been reports of a 2 valve setup with a check valve but I do not have a photo of that type.
ALWAYS make sure the AC power switch is OFF (shown with a safety pin through it) before draining the water heater. Not all water heaters have an AC power option.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW