Venting mainline? Yes or No?

[Tube Tamer]

We have 1900' of mainline. 1600' of 3/4" and 300' of 1/2". Upper 800' is 300' of 1/2" and 500' of 3/4" and has pretty good drop. The 1100' balance follows the natural slope of a creek bottom, not much drop, to the storage tanks. My question is do we need to vent the upper end of the mainline? My reason is the first day we tapped about 160 and had about 200 gals of sap in 5 hours. this was without the upper end being tapped and possibly some venting was occurring. Since we tapped the upper end we have had equally warm days but very little run. Could this be due to lack of venting? Would appreciate any help. Thanks.

[Brian]

Do you have vacuum? With vacuum you should not vent your mainline, with a gravity system "yes" it should be vented.
BRIAN

[Salmoneye In VT]

There are conflicting schools of thought on this...

Depending on the picth overall, a gravity system does NOT have to be vented...In some cases it is best...Some not...With a good drop in elevation, once the lines fill, it actually will create it's own vacuum and you will get greater amounts of sap...If, like what you seem to be seeing in your case, there is a long run of only slight drop, you may indeed need to vent at the farthest point of each branch, and you will never be creating a natural vacuum...

Only real way to figure it out is to try it for your specific situation...

See also the link below for one of the best sapping resources anywhere on the Net!

Hope This Helps!

http://ohioline.osu.edu/b856/b856_33.html

<a href=http://ohioline.osu.edu/b856/b856_33.html>Ohio Maple Producers Manual</a>

[Chris S]

I did not get a run on Tuesday (Rochester) either despite the warm up. The problem was the 5 degree morning (too cold). I doubt that there is a problem with your lines, the problem is with the weather> :( Good luck, it looks like a good day Saturday with temps in the mid 40's :lol:

Chris