tapping below the lateral

[emti]

Now that dust has settled on the season I have a question/observation on tapping below the lateral. It has been shown than tapping below the lateral does not affect sap production. What I saw this year has me confused. Some drop lines were "bowed" and some were straight. The sap would partially fill the 5/16 drop line and then "stall" part way up to the lateral. There was good vacuum measured at the tap. (25 inches +) The tree gas bubbles were present .If you pulled the tap the dropline would clear and after reinserting the tap the dropline would fill to a certain point and stop.Is it a case when the tubing being full of sap, so no vacuum was present at the tap hole and just relying on tree pressure?? Or is it an illusion and the sap was making it into the lateral but not as visible as when tapping above the lateral? Thanks emti

[RC Maple]

I have wondered about this as well. Most all of my taps on tubing are above the lateral for now but would eventually like to use the entire tapping band. The taps below the lateral always seem to have sap in the drop but I never see it going up into the line. If all the taps were below the lateral, would just as much sap make it to the tank?

[RC Maple]

I thought I'd renew this thread. The discussion was started last June, and it's had a lot of views but not replies. I've still been thinking about the question. A little background - the woods is flat and even with tapping higher at the end of the line, my sight level shows I have tried to maintain a barely perceptible slope. I'm using a 4008 Surflo with 3 5/16 lines with 2-6 taps each. Small setup - I know. I will be making new drops for 2025 for these lines and have been thinking about tap placement and being able to use the entire tapping band. My vacuum gauge at the manifold is showing 25 to 29 in depending on the day and the gauges at the end of the laterals are averaging 20 in of Hg. Must be some small leaks I couldn't find even with a detector (or slight sags due to lack of slope). I now have one tap that is below the lateral and it always seems to have sap in it during the season. Even where drops from taps above the lateral loop below the lateral there can be sap sitting there too. What should I expect to see from a setup like this if a number of taps where below the lateral? Is there a minimum level of vacuum that makes tapping below the lateral an equally good way to get sap in the tank?

[maple flats]

I attended a presentation by Dr Tim where this idea was mentioned. He said it works well and is often used by the larger producers. Go for it! While big producers are not using a little diaphragm pump, there should be little if any loss of flow by tapping below the lateral.

[tcross]

there's some studies UVM has done. i believe on their site the research is there. i want to say dr tim said you'd need around 20" or more to see good results with taping below the lateral. i have a good amount of trees where i tap below the lateral. i run 27-28 " and i seem to have good luck with it. they will take a little longer to thaw out and get running but all of mine run well. i use check valves also, which i think is a really good idea when tapping below the lateral specifically.

[Maple Hill]

Are they tapped straight down or do you make a loop?

[tcross]

i make a loop. that way the sap is less apt to go back into the tap hole. i tend to make a little longer drops when i know it's a tree that's going to be tapped below the lateral.

[RC Maple]

I just watched this video from UVM: https://www.youtube.com/watch?v=3EUsr9Rnajs It was done over a couple of years and showed that whether above or below the lateral, with good vacuum, yields were statistically the same. The vacuum provided in the study was ~25 in Hg, a little higher than what I am averaging on the gauges at the end of the line. So far, after just three years, most of my taps have been high enough that I haven't even had much of a loop in the drop going below the lateral. Going forward though I will be having more of that and a chance to see how they do.

[DRoseum]

Using CV spouts when tapping below the lateral is also helpful to prevent backflow when freeze happens.

[DrTimPerkins]

Tapping below the lateral is a good approach to maximizing the tapping band and is especially useful if you have trees in which the tapping band above the lateral has been peppered pretty hard for several years (older, slow-growing trees that had multiple 7/16" spouts put in them, cluster tapped).

If you do try tapping below the lateral, you want decent vacuum (at least 15" Hg at the spout). In addition, it is good to use CV spouts and it is good to have the spout exit facing down so there is a small loop created at the bottom. This will help to prevent sap from pooling right in the spout for frost-heaving and for sanitation.

The following are good resources to look into:

https://www.youtube.com/watch?v=v-EEYgL7Lt0&list=PLZP4fDl-nB9-4aZkQyDR070QpxcAr02q5&index=6&t=6s

https://mapleresearch.org/pub/m1216belowlateral/