Nice looking TT. Your 2017 might still have the small sticker showing you where to look. I don't have a Salem, but in terms of looking, I can tell you my low point drains were inside the frame rails covered in foam. There is a 'low point drain' sticker on my 2018 TT and I still couldn't see them without laying on my back.
Mitch in MN
2018 Patriot (Grey Wolf) 23MK travel trailer
2011 Durango 5.7L and OEM tow package