I believe I read once that, on a hill rack they used to use a sight glass,but, it is NOT inline w/ the liquid line, but, instead it has 2 -1/4 " lines that attach it to the side of the liquid line.
Is it true that this style of piping the s/g it is used solely for moisture indicating only and NOT for determining liquid content.
I can try and dig out my old Hill books, but I'm trying to avoid that If possible.