Yeah, been there done that!
The first time I winterized I use five gallon jugs of antifreeze before I realized I was filling the dang wh! Then a couple of emails to the dealer and manufacturer eventually located the bypass valve.
No! Wait! I bought the rig winterized. I found the bypass the first time I took a shower!
Ten seconds of warm water folowed by freezing cold! Yep, now I remember! I learned where the bypass was fully lathered and wrapped in a towel!
Chet