The 5/16 used for drops has the advantage because in a 5/16 tube the air (gasses) can pass the sap, in 3/16 the air does not pass the sap. Thus, using 3/16 drops pulls more bacteria contaminated sap back into the tree. The sap leaving the tree is bacteria free, it gets contaminated in the tubing and the taps/fittings.
I use a lot of 3/16, but I have no 3/16 drops. All of my drops are 5/16. I used to change out every drop on a 3 yr rotation. After Dr tim told me it was not necessary, I've now gone to just changing the taps, tees and inline fittings every year. I also clean the tubing shortly after the season using calcium chloride and again in the fall, before things freeze up, then I rinse well. 30 minute minimum contact time works well.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.