Poor man's checkvalve

[Groves]

Ok, I'm on buckets on the ground.

There is a tension in the bucket-on-ground world between putting your tube well into the bucket such that it's not easily dislodged, and putting your tube barely in the bucket so the tree doesn't suck any sap back up.

In the vacuum world the checkvalves prevent the sap from moving back up, and not only stem sap loss, but also contamination. Got it.

I don't think the checkvalves work very well on gravity, but I had an idea.

In order to prevent the tree from sucking sap, all I really need is some sort of air gap. Keeping the tubing above the level of the sap in the bucket is the normal way to produce this gap, but can also lead to the problems of tubing falling out, finicky placement, etc.

Why wouldn't I just drill or melt a small hole in the top of the spile? or the top part of the tubing next to the spile?

Could this allow me to go ahead and keep plenty of tubing in the bucket, while preventing the trees ability to suck it back up? We all hate how that micro hole in our drinking straw messes the whole system up. Same principle.

I guess in theory the hole in the tubing could go anywhere above the bucket, but then you have tubing with a hole in it, which might be problematic in future years.

Would a super small hole near the spile introduce too much contamination?

[DrTimPerkins]

In order to prevent the tree from sucking sap, all I really need is some sort of air gap. Keeping the tubing above the level of the sap in the bucket is the normal way to produce this gap, but can also lead to the problems of tubing falling out, finicky placement, etc.

Why wouldn't I just drill or melt a small hole in the top of the spile? or the top part of the tubing next to the spile?

The subject title is a somewhat incorrect. This is not a check-valve, it is a vent (or an intended leak). In general, venting of tubing systems is a bad idea. You lose 1/3-1/2 of your sap yield (depending upon several things). Not sure how microventing will affect the results, except for the fact that a 3' long piece of tubing running down into a bucket will generate 2.65" Hg vacuum. You would lose that if you vented. Perhaps a better alternative would be to put a pinhole in your tubing just above where the tubing goes into the bucket. This will accomplish the same thing (tree will suck air instead of sap), but you'll still get the (small) benefits of vacuum.

[Groves]

the fact that a 3' long piece of tubing running down into a bucket will generate 2.65" Hg vacuum

How does this work, exactly?

I can see how filling a tube full of liquid and then stopping off the top and letting gravity pull on the column of liquid can produce a vacuum at the top.

In practice, though, the drip of a tree can never fill the tube, can it? I mean it runs out preventing the seal that produces the vacuum. In a very small tube I suppose capillary action can keep the tube from clearing, but 5/16" tubing?

Clearly, I don't understand all that's going on.

[cpmaple]

I used 5/16 tubing last year for the first time into pails. I seen that happen on about 20 of the 50 i put out. Trees were running hard so i could only say that it was the amount of sap there at the time to start the process and they stayed that way all season. seem to get a little more from those trees then the ones that didnt do it. cpmaple

[DrTimPerkins]

How does this work, exactly?

I can see how filling a tube full of liquid and then stopping off the top and letting gravity pull on the column of liquid can produce a vacuum at the top.

In practice, though, the drip of a tree can never fill the tube, can it? I mean it runs out preventing the seal that produces the vacuum. In a very small tube I suppose capillary action can keep the tube from clearing, but 5/16" tubing?

Clearly, I don't understand all that's going on.

As long as you do NOT have any leaks in the spout or tubing, the sap will fill the tubing and create a suction on the top (like filling a straw and putting your finger on the top....the vacuum holds it in until you take your finger off).

The same thing happens in vacuum tubing.

The sap has enough capillary action so that it readily can fill a 5/16" tube. Happens all the time. One little leak though, and it'll run right out.

[SilverLeaf]

The subject title is a somewhat incorrect. This is not a check-valve, it is a vent (or an intended leak). In general, venting of tubing systems is a bad idea. You lose 1/3-1/2 of your sap yield (depending upon several things). Not sure how microventing will affect the results, except for the fact that a 3' long piece of tubing running down into a bucket will generate 2.65" Hg vacuum. You would lose that if you vented. Perhaps a better alternative would be to put a pinhole in your tubing just above where the tubing goes into the bucket. This will accomplish the same thing (tree will suck air instead of sap), but you'll still get the (small) benefits of vacuum.

OK, Dr. Tim, I read this yesterday, and have been trying to wrap my brain around this, but not quite getting it. :confused: If we're talking about 3' drops to a bucket, I understand how venting it would eliminate any (small) vacuum benefit there. But in effect wouldn't this just make it the equivalent of a bucket spile that drips into the bucket? In this thread (http://mapletrader.com/community/showthread.php?t=10750) yesterday you said that buckets on trees and a new tubing system would produce the same. But reading this current thread it sounds like a new tubing system (even as simple as 3' drops to buckets) would produce just a smidgen more, due to the vacuum benefit. What am I missing here?

Many thanks!

[DrTimPerkins]

Whether you get more sap from a bucket tree or a gravity tubing operation depends upon a lot of things. If you compare a brand-new tubing system to a dirty old spout and bucket, the tubing wins. If you compare a grungy old tubing system to a clean spout and bucket, the bucket wins. If you have roughly equal systems (in terms of microbial contamination) and no natural vacuum, they should be roughly equal in sap yield.

[DrTimPerkins]

Futher explanation....wouldn't let me do it all in one post.....

A spout and bucket operation will have zero additional inches of vacuum.

A vented tubing system, or a spout with tubing into a bucket that is vented (at the top) will have zero additional vacuum.

An UN-vented tubing system with sap running downhill in a 5/16" lateral line WILL have some additional vacuum. The amount will be proportional to the number of taps, the distance downhill, and a couple of other factors.

An UN-vented spout and dropline into a bucket will generate a coupe of inches of additional vacuum (when the sap is running).

[SilverLeaf]

Ok, that clears things up a bit. Bottom line, as it pertains to this thread: if you're going to put up with a little bit extra contamination risk from tubing (assuming the tubing isn't brand new), then you better make sure you're at least getting the most benefit from that tubing (vacuum) that you can.

Thus, don't vent at the top!

[Groves]

How does the benefit of a 3ft tube, and it's 2.X" of vacuum compare with the benefit of tapping low in the tree?

[DrTimPerkins]

How does the benefit of a 3ft tube, and it's 2.X" of vacuum compare with the benefit of tapping low in the tree?

The benefit (from a pressure perspective) is essentially the same. You're simply trading one for the other. However you shouldn't tap really low year-after-year as this might result in cluster tapping.

[Toblerone]

Hmm. Very interesting. So the tubing effectively/virtually (from a pressure perspective) moves the taphole level to that of the end of the tubing. I think I'll be sure to put my sap sacks on trees with room to tap down low, and put tubing on the trees that require higher taps. Does that make sense or is all of this too little to worry about, from a pressure perspective?

[DrTimPerkins]

Hmm. Very interesting. So the tubing effectively/virtually (from a pressure perspective) moves the taphole level to that of the end of the tubing. I think I'll be sure to put my sap sacks on trees with room to tap down low, and put tubing on the trees that require higher taps. Does that make sense or is all of this too little to worry about, from a pressure perspective?

We're talking "marginal" increases. An intermittant 2.5" Hg increase would mean a 5% or less effect in sap volume. Real....but not so important that you want to risk cluster tapping of the tree around the base.