Mane line vent

[Brokenridge farm]

On mane line without vac. do I vent the end of line.

[WESTVIRGINIAMAPLER]

No, because any opening is sucking bacteria into the mainline. Everything needs to be sealed tight.

[shane hickey]

I have asked the same question and everyone told me no. They told me it wasnt a good idea, I still couldn't believe them. So this year I have 2 woods on gravity. I am going to try it on 1 and not the other to see if there is a difference in production. I let you know what I find out after this season.

hilltop maples

[Haynes Forest Products]

What happens if the runs are a nice down hill run the sap will start to create a natural vacuum. Not some big 10HGs but enough to get the sap moving and help out the dips. Plus I believe that if the line freezes and its vented you wont get that slight push of the warmer sap past the frozen areas and you could get sap running out the back:mad:

[PerryW]

I get natural vacuum from my 5/16" lateral lines, but unless your gravity mainlines are severely overloaded, I doubt the mainline would ever get filled up enough to create a natural vacuum. In a properly operating mainline, the sap runs along the bottom of the pipe like water in a gutter which produces no natural vacuum..

So I can see no advantage to venting the mainline. Just one more place to introduce bacteria and a possible place to lose sap if the mainline freezes up.

[highroadsyrup]

This has been a question we have wondered about for years. I started closing the end taps a few years ago, I couldn't see any big difference in sap yeild. It always made my Dad feel better with the line vented :lol: I have 500 c/v out this year, some will have the end tap vented and some will be closed. I am tracking sap a little more seriously this year so maybe I will know for sure.

[argohauler]

I'm on gravity flow and vent the back end of the main line. On the last manifold or star, I hook on a piece of line 5 or 6' long and tie it up on the anchor tree. My uncle does this as well. It's handy when you go to wash the lines. Everything gets pumped out that vent hose and when it runs clear and doesn't foam on the ground anymore you pinch it off with vise grips, then do your lateral lines.

I also vent every lateral line. I watched the sap just sit there in the line. I pulled the end cap and a way she went. I put a 16 -18 " chunk of line on the end tee with a splicer on the end of that and a string to tie it to the end spile.

As far as bacteria goes, my syrup quality has been fine.

[PerryW]

Argo,

Certainly, if your laterals are not vented and you pull the end tree tap, the sap will race down the pipe. This is the natural vacuum working. It will flow like crazy until the line drains, then it will slow down again. I guess your method would reduce the amount of sap stuck in the lines, but would also reduce the natural vacuum. Certainly food for thought.

Actually, my laterals are often unintentionally vented by a pesky squirrel. I can usually detect this just by looking at the flow in the lateral. If is see the sap smoking down the pipe, but with a large percentage of air in the lines, I know there must be a leak and I'm sucking air. I always rush to patch this leak because I think the flow capacity of the lateral is reduced if if mostly air is flowing in the pipe.

What would be nice is to leave your laterals unvented but as soon as the sap flow stops, have a solenoid valve which opens the vent and allows the lines to drain. However, this would most likely be impractical and prone to mechanical failure.

I think the bacteria issue is not a syrup-quality issue, but a length-of-season issue. After all, people make decent syrup with buckets which are totally exposed to the air. I think the point about the bacteria it that is makes the taphole dry up quicker. My buckets certainly seem to have a shorter season than my (gravity) tubing.

[ennismaple]

There's lots of research out there about vented vs non-vented gravity laterals. Over the course of a season non-vented gravity should produce 32% more sap (see UVM Proctor Research highlights 2006-2007, page 2, first paragraph).

As for the original question, venting a gravity mainline would provide no benefit as the mainline does not flow full so there's lots of air above the sap to allow it to freely flow downhill.

[Haynes Forest Products]

I also think there is a false reaction to alot of sap with bubbles in it rushing down the line verses slow moving sap in a full line.