Looping Drop Lines

[spud]

I was wondering how much production (if any) is lost because of a drop line with a loop in it. I always try to keep my drops straight but it does not always work out. I have seen taps below the lateral line and always wondered if production is being lost because of it. It seems like vacuum would be restricted big time but has any research ever been done on this? If you look at sap flowing through a lateral line you would think vacuum is being shut off from the trees above it but it's not. I am just wondering how much vacuum and production is being lost because of sagging drops. I don't see anything on the PMRC site talking about this. Thanks

Spud

[Scribner's Mountain Maple]

Good question. I have often wondered the same. I also try to avoid the loop, but there are times when the tap hole is low and the loop is impossible to avoid. I don't have any answers, but know many large producers where I have seen many tap holes at or below the lateral line. They are still making a ton of syrup.

In theory it would seem as though vac would be disrupted much like a sag in a main line, right?

Ben

[Drew Pond Maple]

I think the sap in the dropline would be like a p trap under your sink. One pint of sap in, one pint out. Kinda like the sap in the loop between the hook connector and the saddle fitting that has sap in it. once the tree starts to freeze it would start to suck back up to the tap hole possibly. Not 100% sure though

[spud]

I did see on a PMRC report the use of a duel line system. I think it was to keep high vacuum on the tap hole at all times even when one of the drops had sap in it. Dr Tim should be able to answer that. It just seems like a single drop with a sag in it would cause a lose of vacuum to the tap hole.

Spud

[DrTimPerkins]

The best answer to this question is....we don't know how much negative influence it has. If it has any effect, it would not be positive. Try to avoid the situation if possible, but I understand it isn't always possible. Happens to us at times as well.

Yes, as Spud indicates, we've been doing a lot of work on dual-lateral/dual-dropline systems. This would largely prevent the sap from pulling back into the taphole, even if the drop did fall below the lateral.

[jrgagne99]

Reduced vacuum transfer through the sap is one issue. Frozen sap in the sag in the morning is probably the bigger issue. Depending on weather, it could cause you do loose an hour or two of production waiting for the drop to thaw out, maybe more. Contrary to a frozen sag in a mainline, frozen sap in a drop has a localized effect, but should probably still be avoided.

That's why I use 18" 10 24" drops, not the 30-36" that some guidelines suggest.

[Jeff E]

Here is another way to look at it.
I agree that there would be a certain amount of Vac loss if the sap has to be pulled up to the drop. However, I use the traditional 'sap ladder' in many places in my woods. I have one that lifts sap up 5/16 tubing over 12'. I have a gauge on the high line, and one on the low line. The typical situation when I am checking this area is 24" of vac on the high line, before the lift, and 21" of vac on the low line. In this situation, I was able to add about 120 trees.
My point being that in 12' of lift, losing 3" of vac indicates to me that lifting sap say 6" in a drop line loop will not have a significant impact on that tap.

There is a positive use of the loop as well. I can tell instantly if I have a leaky tap, adaptor, or a hollow tree. This allows me to keep the woods vac very tight, much easier. For me, that was a trade off I was willing to take.

I know on frozen mornings, my laterals will be frozen anyway, so having additional sap frozen in the drops is not a big deal. I could take a few extra minutes to thaw these out, but I dont think I am losing sap because of it.

Keeping the vac high is what I am looking for, and having small dips in the drops really helps me. So I have been doing it on purpose.

[adk1]

What about not on vac?

[markct]

Regardless of the shape of your drops, if they arnt holding sap in them (which will freeze of course) then that means that you have a leak which is worse than any little bit of time lost in flow while they thaw.

[jrgagne99]

Here is another way to look at it.
I agree that there would be a certain amount of Vac loss if the sap has to be pulled up to the drop. However, I use the traditional 'sap ladder' in many places in my woods. I have one that lifts sap up 5/16 tubing over 12'. I have a gauge on the high line, and one on the low line. The typical situation when I am checking this area is 24" of vac on the high line, before the lift, and 21" of vac on the low line. In this situation, I was able to add about 120 trees.
My point being that in 12' of lift, losing 3" of vac indicates to me that lifting sap say 6" in a drop line loop will not have a significant impact on that tap.

There is a positive use of the loop as well. I can tell instantly if I have a leaky tap, adaptor, or a hollow tree. This allows me to keep the woods vac very tight, much easier. For me, that was a trade off I was willing to take.

I know on frozen mornings, my laterals will be frozen anyway, so having additional sap frozen in the drops is not a big deal. I could take a few extra minutes to thaw these out, but I dont think I am losing sap because of it.

Keeping the vac high is what I am looking for, and having small dips in the drops really helps me. So I have been doing it on purpose.

I had never looked at it that way. Visual feedback of a leak at the tap hole is a nice "feature" of a having a sag.

[Scribner's Mountain Maple]

Here is another way to look at it.
There is a positive use of the loop as well. I can tell instantly if I have a leaky tap, adaptor, or a hollow tree. This allows me to keep the woods vac very tight, much easier. For me, that was a trade off I was willing to take.

I know on frozen mornings, my laterals will be frozen anyway, so having additional sap frozen in the drops is not a big deal. I could take a few extra minutes to thaw these out, but I dont think I am losing sap because of it.

Keeping the vac high is what I am looking for, and having small dips in the drops really helps me. So I have been doing it on purpose.

This is interesting. Never really thought about this before. If there is no negative effect of the loop, then it's use would be very helpful in leak isolation and maybe more. It would act as a "P" trap like household plumbing does. In our houses, the use of a PTrap is to prevent stinky air from flowing into our homes. Wouldn't the same concept apply to the tap hole. The loop would prevent dirty air from back flowing into the tap hole. And as a result reducing bacteria in the hole? Makes sense to me. What about production I wonder. If this had no negative impact on production, it would function much like a Check Valve. The sap in the loop acting like a ball valve. Of course not quite as good probably, but similar. I would think it would help prevent back flow into the tap. So long as the loop was far enough away from the tap hole.

I would be very interested to learn if there is a negative impact of the loop on Vac transfer to the tap hole. How would/could you prove it. hmm. maybe take a twisty straw, apply suction on one end and measure how much you get out of the other. Then take the same straw, fill the loop with water and reapply and measure vac pressure. That would do it I think. Now for someone to test it. Any takers?

Ben

[Jeff E]

A couple of questions came up: What about on Gravity? I would not do the sag, as there is no value in finding leaks if your not using vacuum. I would make the 5/16 lines as strait as possible to reduce flow restriction.

Would the sag holding sap work like a check valve? I doubt it. When the trees start to freeze, they create tremendous internal 'vacuum'. They will pull that sap right back into the tree, even with high vacuum. I have been out checking for vacuum leaks in the late afternoon, and watched the sap stop flowing in the lateral lines, with 24" of vac on them and then it would start moving backwards in the lines! That baffled me, until I thought about the internal processes going on in the trees, freeze/thaw cycles.

That is why I use check valves now. Stop the back flow at freeze up! I had taps drilled in the 3rd week of Feb, still making sap on April 25. Those taps had the sag in the drop line, and check valve taps.

[Scribner's Mountain Maple]

I actually do think they would perform like a check valve. The sap in the loop will not be pulled up a ft when the vac is on, assuming the loop is at least that far below the tap hole. Unless sap is pushed back up the lateral lines maybe.

What does a check valve do when the vac is on? not much...upon freezing you are saying the vac in the tree will close the valve over the vac from your pump? That would surprise me a little I guess. If that is true, then the check valve is better on that aspect. However, if the sap in the loop freezes at the same time, won't it function exactly the same way?

I must admit on a new system (which most of mine is), I am not 100% sold on need for the CV's. Considering we are in the age of leaving vac on 100% of the time during season which keeps the valve always open. When my lines get 3-5 years old (more bacteria in them), I think I will use CV more.

So if (big if) the loop performs in a similar way, I think everyone would do it. Right?

[DrTimPerkins]

The loop would prevent dirty air from back flowing into the tap hole. And as a result reducing bacteria in the hole? Makes sense to me. What about production I wonder. If this had no negative impact on production, it would function much like a Check Valve. The sap in the loop acting like a ball valve. Of course not quite as good probably, but similar. I would think it would help prevent back flow into the tap. So long as the loop was far enough away from the tap hole.

Won't work. In a DWV (drain-waste-vent) system like your typical household, the system is VENTED, so there is no strong pressure gradient between the pipe and the toilet, and any gases are most likely to go up the vent (otherwise you might have some real surprises sitting on the toilet or standing at the sink). In a closed tubing system under vacuum, if you have a leak on the outlet side, the air has nowhere to go but backward (towards the tree), and will push any sap (and microbes) along with it....right back into the taphole. A loop is a very minor impediment to this....it'll barely slow the sap down as it travels back. It would take a loop tens of feet in diameter to create any substantial impact on this backward movement. Even so, that wouldn't prevent any sap in the dropline before the loop moving backward.

The negative impact of the loop on vacuum transfer is probably fairly modest given that the tubing (and fitting) diameter is very small and the lumen of the tube is full of a mixture of gases and liquid, resulting in a fairly substantial resistance all by itself (this is the limitation of using 5/16" tubing in pumped vacuum systems). However the loop is definitely a microbial trap of sorts, in that there will be some sap and microbes retained in the loop all the time, and this will inoculate any sap passing through the loop. Of course the small upturn of the lateral line going into the mainline (for leak checking) has pretty much the same type of effect, but probably a somewhat smaller impact than a loop would have.

I guess I'm not sure what advantages putting a deliberate loop in the dropline for leak detection has over simply observing the sap flow in the line without the loop. Either way, the rapid movement of air though the line that is indicative of a leak should be readily apparent, so the loop is not really necessary.

[Scribner's Mountain Maple]

Thanks you Dr Tim. I knew it was something simple like that.:)

I think I will stick with the non-loop approach and use CV's on my system when it gets a little older. Of course as most have pointed out, in some circumstances the loop is unavoidable.

Ben

[DrTimPerkins]

I actually do think they would perform like a check valve. The sap in the loop will not be pulled up a ft when the vac is on, assuming the loop is at least that far below the tap hole. Unless sap is pushed back up the lateral lines maybe.

The loop will not serve the same function as a check-valve in a non-vented system.


What does a check valve do when the vac is on? not much...upon freezing you are saying the vac in the tree will close the valve over the vac from your pump? That would surprise me a little I guess. If that is true, then the check valve is better on that aspect. However, if the sap in the loop freezes at the same time, won't it function exactly the same way?

The loop doesn't function as a check-valve. The trap in a DWV system, which is VENTED by design, is made to prevent the movement of gases backward. The small amount of standing liquid in the trap functions ONLY because the system is vented to the atmosphere, so the very small amount of resistance of moving through water (compared to simply going up the vent) is enough to prevent the gases from bubbling up through your fixtures (toilet or sink). This is not the same as a tubing system under vacuum. You've only got two possible directions...frontwards (away from the tree) or backwards (towards the tree). If the gases move back towards the tree, then the liquid is likely to also move towards the tree.


I must admit on a new system (which most of mine is), I am not 100% sold on need for the CV's. Considering we are in the age of leaving vac on 100% of the time during season which keeps the valve always open. When my lines get 3-5 years old (more bacteria in them), I think I will use CV more.

There is relatively little benefit to be had from using CV adapters or spouts on a brand-new, never had sap through it, system. This is because there are no microbes there yet. Once the lines have been used for a season, they have microbes in them....and unless you do something, your sap yield will drop. There will be a slight effect initially, and it'll get larger the older the tubing gets (as more and more microbes build up.....until about 6-8 yrs when the tubing is about as contaminated as it can get).

In all of our studies the vacuum is left on 100% of the time (unless the power goes out, which we cannot control). If you look closely at flow in tubing systems, it is not 100% steady in the same direction. There are brief periods of time when small amounts of backflow occur (on the order of seconds and backflow of just a couple of inches or less). Different equipment, sizes of operations, # taps on mainline and lateral lines, single or dual-conductor systems will all affect the amount of backflow you get, along with leaks (that we can't predict). So all of these things will help to varying degrees depending upon how your system is configured, and what happens that you can't predict (leaks, power going out, etc.).


So if (big if) the loop performs in a similar way, I think everyone would do it. Right?

If the loop performed in that way, people would use it. However it won't perform in that way, so there is no need to use it, and perhaps some reasons not to.

[spud]

Very good info Dr. Tim thanks so much. I for one had back flow issues last year because my pump would loose it's ring. I was told this was happening because of a small vacuum leak at the releaser. I have fixed that little leak and gained 1 inch of vacuum. My plan was always to start using the check valve on the third year of my tubing. After watching sap flow to the trees and not the mainline two times last year I knew I needed CV2s right away. There are three main reasons I have switched to CV2s for this season. 1) I want to tap early January without affecting my April sap (14 week season). 2) I want to prevent sap from going back into the tree (back flow). 3) I want production numbers like PMRC. A person can leave their vacuum on 24/7 but this will not prevent back flow. If a person is not using CV2s they will have back flow even if they don't see it happening.

Spud

[markct]

Whats a CV2 ? somehow different from a standard checkvalve tap?

[unc23win]

CV2 is the second generation check valve it is Clear and its all one piece and doesn't require a stubby.

[markct]

Ah ok, any advantage to them functionaly? im already setup for stubbys so even tho I wish they made the reg ones clear I don't think I will go changing up now just to get clear taps

[lpakiz]

Market,
I am set up with stubbies also. They are going on their 4th season this coming spring. I think I will change the drop lines after next season, (after the 5th season) at which time I will convert to the CV2.
I found I can remove a 5/16 line from the fitting by heating the line over the fitting for a few seconds with a propane torch until it looks shiny, then pinching the line with a pair of pliers, not too deep to touch the barbs, but deep enough to grab most of the softened plastic. A bit of a twist and most of the line rips away without ever touching the barbs. Gonna try it that way anyway, before I buy all new tees.

[spud]

How much GPT are you getting from your stubbies? How high vac do you run? When do you tap? Thanks guy's

Spud

[Walling's Maple Syrup]

How much GPT are you getting from your stubbies? How high vac do you run? When do you tap? Thanks guy's

Spud On my woods behind the sugarhouse I had 4400 taps last year. 3500 of these were added last year. 900 were five years old on 5 year old drops. 2900 of the 4400 taps were stubbies and old-style cv's. 1500 were the cv2's. I cannot tell you how the cv's did compared to the cv2's because they were all running into the same releaser. I started drilling last year on Jan. 20. First boil- Jan. 31. Last boil- April 17. 33.8 gpt. The day I started pulling taps(april18) sap was still running over 400gph, but had turned buddy at this point. This year I plan to start drilling the first week of Jan. I ran a little over 27" of vac. last year.
Neil

[spud]

Thanks Neil,

Those numers of 33.8 gpt are very good. What is the smallest tree size you tap? I hope that by using the CV2s and tapping a little early I too will get 33.8 gpt. I wish you the best in the up coming season.

Spud

[sapman]

The biggest advantages I found of CV2s over the originals are one-piece design, so no chance for leak between stubby and cv, and the taper on CV2 seems more "perfect". Leaks were almost non-existent last season (after a few days of fine-tuning, of course), even after freezes. Oh, and the clear spout is nice, too.

[Walling's Maple Syrup]

Thanks Neil,

Those numers of 33.8 gpt are very good. What is the smallest tree size you tap? I hope that by using the CV2s and tapping a little early I too will get 33.8 gpt. I wish you the best in the up coming season.

Spud Spud,
The bottom part of my woods(approx15 acres) was pasture some 50 years ago, therefore there are alot of pole-sized trees(mostly maple) This section is thick with trees and I have probably 500 or so taps on trees as small as 6"(needs thinning in this section if I ever get to it). In alot of spots 2 smaller trees are close enough together where I just put 1 drop between the 2 trees and tap each one every other year. Good luck to you this year as well.
Neil