gravity drop line question

[randolphvt]

I have one line with about 10 taps on it. Last year I had issues with no drip-gravity (no pump).
If I pulled the tap at the end of the line (furthest from collection bucket) it would run. Do I need to put a loop in the line as a pressure release.
In my mind, I thought of the soda straw. You know as a kid, you would put your straw in your drink then plug the top of it and you can lift
your soda inside the straw because there is no pressure release.
Thanks in advance for replies.

[Sugar Bear]

I have one line with about 10 taps on it. Last year I had issues with no drip-gravity (no pump).
If I pulled the tap at the end of the line (furthest from collection bucket) it would run. Do I need to put a loop in the line as a pressure release.
In my mind, I thought of the soda straw. You know as a kid, you would put your straw in your drink then plug the top of it and you can lift
your soda inside the straw because there is no pressure release.
Thanks in advance for replies.

I have had this problem before and everybody else who does this kind of thing will.

The disadvantage of venting the end of the line, which is what you did, is that you are letting dirty air get closer to or even at your tap holes.

You may not have enough pitch to overcome friction and you are sap locking, in which case you are better off on drops to buckets, which will not "fan" fresh dirty air through the system perpetually as sap flows, like venting the end of the line will.

But if you are steep enough then ....

1) Slope everything down hill as much as possible. Tight and straight. No sags.

2) After the lowest tap in your run, try to have as long, straight, and steep of a run to the collection barrel as possible. Straight and Steep are the most important in this section of the run. Long is best at about 75 feet long and steep as possible for 10 taps. Ultimately this section of tubing is the engine behind any natural vacuum you are going to generate. And if it is steep enough you should be able to generate at least 18 inches at the top of the run on 10 "good" taps on 5/16 tubing.

I have no experience with 3/16 but they say 3/16 will do better on less slope, but has the disadvantage of clogging fittings much more easily the 5/16.

[DrTimPerkins]

Do not vent the lines (unless you want less sap).

It is an optical illusion of sorts. As soon as you pull the plug, the sap runs out quickly. But if you watch for little while you'll see that it soon stops, then you'll get one drop in (from the tap) and one drop out. What you'll also get is air being sucked into the line, which carries microbes and hastens taphole drying.

In short, venting will result in considerably lower sap yield on a tubing system.