5/16 drops vs 3/16 drops to 3/16 laterals

[pprus]

This fall I was talking to another producer and he mentioned that he was going to switch to a 5/16 drop instead of the 3/16 drop to a 3/16 lateral with the idea that the tree cannot draw the sap back in when it is getting cold. I am curious if anyone has experience with this type of set up and did you find this worked better? I replace all of my taps and drops every year. I am running 3/16 laterals and from top to bottom I have over 200' of vertical drop or an average of 13% slope and everything is just using gravity. I have tried to do a little research and have not found much.

Thank you for your help.

[blissville maples]

The 5/16 drop will eliminate some of the drawback, I would recommend atleast 3' drops. Every tree is slightly different but 5/16 can draw back several feet wjere 3/16 can be several feet, 5-15'

[pprus]

The draw back decreases sap yield? It would also make sense that as the sap is drawn back it would bring bacteria which would cause the tap holes to close up sooner decreasing sap yields as well?

[maple flats]

The 5/16 used for drops has the advantage because in a 5/16 tube the air (gasses) can pass the sap, in 3/16 the air does not pass the sap. Thus, using 3/16 drops pulls more bacteria contaminated sap back into the tree. The sap leaving the tree is bacteria free, it gets contaminated in the tubing and the taps/fittings.
I use a lot of 3/16, but I have no 3/16 drops. All of my drops are 5/16. I used to change out every drop on a 3 yr rotation. After Dr tim told me it was not necessary, I've now gone to just changing the taps, tees and inline fittings every year. I also clean the tubing shortly after the season using calcium chloride and again in the fall, before things freeze up, then I rinse well. 30 minute minimum contact time works well.

[pprus]

Please correct me if I’m wrong but wouldn’t the 5/16 drop decrease the affect of creating vacuum using the 3/16 or is the drop short enough that you still get vacuum? The benefit of using 3/16 is the vacuum that is created to pull more sap out of the tree.

[Mead Maple]

I too run 3/16" lines but utilize 5/16" drops. As mapleflats indicated, I see significant gas being passed using this method. One thing I have noticed is while the larger drops/tap has a significant amount of gas in the line, once the 3/16" is full and has begun the "pulling/vacuum" process, there is minimal breaks in the sap column leading me to be become a true believer in the 3/16" despite some of it's flaws (vs 5/16"). I will continue to use this method until I ever decided to go vacuum on everything. As an FYI, I had 4 lines last year varying from 15-30 taps, each with a vacuum gauge on them. Now these aren't high end gauges but all 4 lines consistently read over 25hg. Several were pushing close to 28hg on good runs. Now this was on virgin trees with all brand new lines/taps/t's/etc. But pulling the tap allowed me to experience that "wwwhhoooossshhhh" sound of vacuum being lost. Hope this helps you out.

[eustis22]

> I would recommend atleast 3' drops.

Really. Is that vertical? How high off the ground is your lateral? Most of my drops run 12-18 inches only.

[mainebackswoodssyrup]

> I would recommend atleast 3' drops.

Really. Is that vertical? How high off the ground is your lateral? Most of my drops run 12-18 inches only.

3' is a good standard. Sometimes I wish we had some longer ones. Try it- you'll be able to get around the tree and different heights much easier. If you have a high lateral area and the drop is too long, just wrap it around the tree and find a good spot to tap. Within reason, you can't make drops too long. 12" is very much limiting the areas to tap on a tree.

[eustis22]

I'll try that this season...most of my laterals start out between waist and chest high.

[maple flats]

You should not even try to make your drops go straight up. That would give you an extremely narrow tapping band after 2-3 seasons. You just want to be able to reach all sides of the tree. Also, look for last year's tap hole, on gravity (except natural vacuum) move over from last years hole 2-3" and up or down 6". With vacuum, either natural or with a pump, tap on the opposite side of the tree. In year 3, go half way between year 1 and 2 tap holes and year 4 go opposite year 3. Then year 5 go between the 2 holes that will get you farthest from year 5's hole. Never try to tap all on the sunny side, that way in year 2 all are on the north side. The way I do it and train any helpers to tap, is to drill hole 1 on the side facing you as you approach the first tree, then on tree 2 tap on the opposite face, tree 3 the face halfway between where you tapped trees 1 and 2. Keep following that type of pattern. Then you will end up with about the same % of taps on each face, giving you the best sap flow every year, not far better one year and poor the next. By the way, the face you tap has little to do with your season's total, but it does affect time of day and season flows. South facing start earlier in the day, north flow later as it cools down. South facing flow earlier in the season, north facing last later in the season. As long as you keep the balance of faces tapped you get the best overall year to year.
If you use any other pattern, just make sure not to favor any one face of the trees.

[DrTimPerkins]

Please correct me if I’m wrong but wouldn’t the 5/16 drop decrease the affect of creating vacuum using the 3/16 or is the drop short enough that you still get vacuum? The benefit of using 3/16 is the vacuum that is created to pull more sap out of the tree.

Let's say you have a 3' long 3/16" dropline going straight up and filled completely with sap. You'll theoretically create 2.6" Hg of vacuum at the taphole. However, you will also lose 36 inches of pressure head, which equals 1.3 psi OR 2.6" Hg vacuum. Essentially they cancel each other out for a good part of the sap run. Now if you still have good vacuum after the wood above the taphole is drained you "might" collect a little more sap that way, but it'll be a fairly small amount.

By using 5/16" drops on 3/16" lateral lines you keep more sap from being pulled back into the tree (backflow) during the freeze cycle, which helps in keeping the taphole viable for longer in the season.

Unfortunately this is one of those instances where physics dictates you won't get something for nothing.

[csievers]

By using 5/16" drops on 3/16" lateral lines you keep more sap from being pulled back into the tree (backflow) during the freeze cycle, which helps in keeping the taphole viable for longer in the season.

I am guessing this benefit would not apply if using check-valve taps?