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.
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
Google Custom Search For Sunline Owners Club