Designing 3500 tap tubing system.

[DrTimPerkins]

Not to toss cold water on the 3/16" tubing craze, however we've found that (in a high vacuum tubing system) 3/16" tubing is considerably more susceptible to progressive plugging issues UNLESS you flush your tubing annually. If you can't flush, I'd be wary of adding a lot of 3/16" tubing and would suggest sticking with 5/16" tubing. If you can flush, then 3/16" tubing will certainly provide a significant amount of additional benefit in a hybrid (pumped + natural vacuum) system. In this case, "dry cleaning" (pulling taps with the vacuum on) does NOT count as flushing. You need an actual flush with water or preferably with a sanitizing solution.

In addition, 3/16" should NOT be used on flat land or in a low slope setting. Too much friction with the tubing resulting in backpressure and reduced sap yields.

In areas with good slope (elevation drop) where it can be flushed annually, 3/16" tubing works very well either with pure natural vacuum or in a hybrid system.

[Sugarbush Ridge]

Dr Tim; "You need an actual flush with water or preferably with a sanitizing solution." What kinds of sanitizing solutions are out there?

[DrTimPerkins]

What kinds of sanitizing solutions are out there?

There are several, including: water, bleach solution, hydrogen peroxide based cleaners (Premium Peroxide), various commercial tubing cleaners. Just don't use isopropyl alcohol if you're in the U.S. Pay attention to the "contact time" and any rinsing requirements associated with each sanitizer.

Note that this does not constitute an endorsement of any one particular type of sanitizer.

[abbott]

Not to toss cold water on the 3/16" tubing craze, however we've found that (in a high vacuum tubing system) 3/16" tubing is considerably more susceptible to progressive plugging issues UNLESS you flush your tubing annually. If you can't flush, I'd be wary of adding a lot of 3/16" tubing and would suggest sticking with 5/16" tubing. If you can flush, then 3/16" tubing will certainly provide a significant amount of additional benefit in a hybrid (pumped + natural vacuum) system. In this case, "dry cleaning" (pulling taps with the vacuum on) does NOT count as flushing. You need an actual flush with water or preferably with a sanitizing solution.

In addition, 3/16" should NOT be used on flat land or in a low slope setting. Too much friction with the tubing resulting in backpressure and reduced sap yields.

In areas with good slope (elevation drop) where it can be flushed annually, 3/16" tubing works very well either with pure natural vacuum or in a hybrid system.

Good info, but now I want more details. What constitutes enough slope? Does that vary depending on how many taps you put on a line?

If plugging is a concern, would it be wise to flush the lines again in the fall (or just run the vacuum and check for plugs then) after bacterial growth has slowed? Why is plugging more of a problem on high vacuum and what is high enough to be high vacuum (gravity systems on 3/16 achieve high vacuum too don't they?)

I can handle a little cold water if it means I end up with the right system. Thanks for all your help!

[GV2]

In addition, 3/16" should NOT be used on flat land or in a low slope setting. Too much friction with the tubing resulting in backpressure and reduced sap yields.

Dr. Tim, would you consider 25 foot of 5% average drop from lowest tree, inadequate, borderline, or ok?

[DrTimPerkins]

Good info, but now I want more details.

So do we. All we know at this point is that there is some sort of long-term (3 yr) progressive loss in production from 3/16" compared to 5/16" tubing in a high-vacuum environment. We suspect it is progressive plugging, but don't know for certain. We intend to investigate solutions next season, so just realize that we are dealing with incomplete information, and that the story can (is likely to) change as we learn more.

What constitutes enough slope? Does that vary depending on how many taps you put on a line?

Tim Wilmot has published a number of papers on this, as has Steve Childs. I suggest you read their publications to answer those questions.

If plugging is a concern, would it be wise to flush the lines again in the fall (or just run the vacuum and check for plugs then) after bacterial growth has slowed?

Flushing in the spring will remove the sap residue and reduce growth. You could again in the fall, but that would only serve to increase the cost of this activity. We don't know yet what the most effective ways to clean 3/16" tubing is, or whether simply "dry cleaning" (pulling with vacuum on) and replacing drops periodically will suffice instead. We do know that flushing at the end of the season will help reduce plugging issues though, so that is the interim solution until we know more.

Why is plugging more of a problem on high vacuum and what is high enough to be high vacuum (gravity systems on 3/16 achieve high vacuum too don't they?)

Vacuum is vacuum is vacuum. Doesn't matter how it is generated in terms of this issue. It is likely to be an issue with any 3/16" tubing system.

[DrTimPerkins]

Dr. Tim, would you consider 25 foot of 5% average drop from lowest tree, inadequate, borderline, or ok?

Do you mean a 25' total drop in elevation from the lowest tree averaging 5% in slope? If so, yes, that is plenty to generate decent vacuum. You should be running around 18-19" Hg in that setting assuming your system is tight.

[GV2]

Do you mean a 25' total drop in elevation from the lowest tree averaging 5% in slope?

Yes 25' total drop. I think I will give it a try. Thank you!

[WESTVIRGINIAMAPLER]

I'll jump in here some with cleaning issue. We had a good discussion on cleaning at the start of the Friday seminar on 3/16 I did at CDL open house with attendees and Tim Wilmot. I have a lot of 3/16 tubing that has been up for 3 years and 3 full seasons and it looks about as good as what I put up 6 months ago. I saw no increase in plugging in it this year even though it was older. Each of the last 3 seasons we have had way above Normal high temps during a lot of the season which should lead to even more issues with plugging. I flush all mine every year including drops and this year I let the taps hang dry a couple of weeks also. I recommend cleaning 3/16 every year and Tim Wilmot was also in agreement that 3/16 should be flushed after the end of each season. I'm using only permeate to flush with no chemicals as I don't like to use any chemicals.

Tim Wilmot stated he didn't feel sucking system dry with vac pump on a hybrid system was sufficient but should also be flushed. I know a lot of yeast of flushed out when I do this. I think another key to advoid plugging is getting the taps pulled quickly and not leaving them in trees way after season.

I will say I'm only running CDL 3/16 semi-rigid and I haven't used any other brand so I can't speak for what it will do. I'm trying different cleaning methods every season to see what works best.

[DrTimPerkins]

Unfortunately you can't really "see" how clean tubing is from how it'll affect the sanitation aspect of yield enhancement. There is very little relationship to what is seen through tubing walls and how good your sanitation is. I've seen tubing that looks quite bad, but most everything in it was dead (and thus didn't really reduce sap yield), and tubing that looked good, but had a lot of stuff growing in it (just not visible). As far as plugging, despite looking closely we don't see a real lot of material plugging in tubing, so hard to say for sure whether it is truly plugging of fittings or whether this issue is caused by sanitation issues in the dropline. Not surprised Tim Wilmot recommended that flushing -- he has suggested that for some time, and we spoke just as soon as our results this year were in. Unfortunately it is also something you aren't likely to easily detect from yields. The yields we are seeing are still VERY good, but the 3/16" is no longer as good or better than the 5/16" tubing after three years. We don't know yet whether it is plugging or sanitation issues. Either way, we'd recommend replacement of drops after 3 yrs anyhow, so we'll probably test that next spring and see if it corrects the problem. In the meantime, with 3/16" tubing it is probably best to flush the lines and replace spouts annually, and consider replacing drops on a 3-yr cycle. We should know by this time next year whether "dry cleaning" (not flushing) and replacement of drops/spouts is sufficient in a 3/16" system of this type.