If you look at the back of the tank you will see a pipe between the intake and output lines of the tank. The valve arrangement can vary from one to three. Your '05 most likely will have either two valves, or a valve and a check valve.
This is a three valve arrangement, but it will give you an idea of what you're looking at.
Then you can test the valve positions for being in by-pass mode by draining your hot water tank then turning on your pump and opening a hot water faucet. You should get cold water coming out of your faucet without filling your hot water tank.
Your 2005 should look like this, this is from a 2004
On the top is a check valve to only let water out of the heater. On the bottom is a 3 way selector valve. You flip that selector to point up and it then bypasses the HW heater. The check does not always 100% shut off but it does shut off a majority if the flow. Sediment from the HW heater can get stuck on the seat I believe. Mine never sealed dead tight but sealed well enough that I only lost about a quart into the HW heater verses 6 gallons to fill it.
Hope this helps and good luck.
PS don't forget to purge the outside shower and the toilet sprayer with RV anti freeze if you have one. Common forgotten winterizing times.