Unfortunately it isn't possible to attach PDFs, but here is the primary figure from the Maple Digest article Dave and I were referring to. It summarizes 10 yrs of research at UVM and Cornell on 5/16" spout/tubing sanitation studies (replacement, cleaning, combination). The story with 3/16" tubing is a little different due to the plugging problems.

Citation is: Perkins, T.D., A.K. van den Berg, and S.L. Childs. 2019. A Decade of Spout and Tubing Sanitation Research Summarized. Maple Syrup Digest 58(3): 8-15. Folks should try to find it and read it before asking a bunch of questions since they are likely to be answered in the paper. We publish the majority of our research there. Back issues are archived online (after 1 yr). A subscription is $10.00/yr. http://northamericanmaple.org/index....-syrup-digest/

Attachment 20338