X2 on what creativepart advises. I have a check valve issue behind my water heater related to my bypass and need to get to it for replacement on our 38Q. I crawled under the rig and found the access panel. Does not look like an enjoyable job getting to it and off, but is likely doable. Will attack mine in a few weeks. Fingers crossed getting the panel off. Not made for old geezers like me. Good luck on yours.
Joe a/k/a "Americanrascal"
2016 Winnebago Adventurer 38Q +tow dolly
8th RV to sit in our driveway in 35 years