Tubing/Tapping Recommendations: 3/16 vs 5/16, rigid vs semi rigid

[FarmallCT]

Hi All,


This will be my second year using tubing for maple syrup production. Last year I put up about 60 taps on Leader 5/16 semi rigid UNI-50 dark blue tubing straight into a 275 gallon tote. This year I am looking to expand to about 200 taps and add some 3/4" mainline.

I am currently stuck between expanding my use of 5/16 tubing, or trying out 3/16 tubing while I do not have much 5/16 up yet. I have heard some pretty solid reviews of 3/16 tubing on this site, but I have a few concerns.

My primarily concern is the need for a significant drop to create vacuum. I have read that a drop of approximately 20-30 feet is desirable to create sufficient vacuum. The area I am looking to tap does have a slight slope, but is mostly gradual with no major drops and could easily be traversed by an ATV/tractor if not for the trees/brush/rocks. Just judging by the eye, maybe a 10 ft drop over 200ft. That might still be a bit more than it actually is. Not sure how to accurately measure it better aside from running some lines and finding level.

I believe it is sufficient for a normal 5/16 gravity system, but am not sure that it would be enough to be worth a 3/16 system. The low point is next to a stream bed next to the road and is not near any current power source. A power post could be put in in the future for a vacuum system if I expand to the point it is desired, but is not readily available at this time.

Additional concerns include needing tools for 3/16 tubing where currently I have managed to put up 5/16 tubing by hand, as well as a discussion with a supplier regarding issues with 3/16 if not on a major slope or if vacuum is installed in the future.


My other main question has to do with tubing types. I started last year with Leader 5/16 semi rigid UNI-50 dark blue tubing, primarily due to it being the cheapest option and just wanting to get started with it. I used this in conjunction with CDL 7/16 spouts and CDL Max Flow Tees w/plug. What is the difference between the different tubing types? Rigid, semi rigid, max flow? I haven't found much describing each and their uses, especially company specific types. Should one type be used for laterals and the other for drops? Could also use some advice regarding differences between taps as well. 7/16, health spouts, antibacterial, check valves, etc. I am still fairly new at this and mostly self taught from reading this forum and watching videos of it being done.

Any other input regarding recommended lines, taps/differences between them, how to connect to the mainline, and mainline size/pitch would be greatly appreciated as well.


Thank you in advance!

Matt

[Sugar Bear]

Hi All,

I am currently stuck between expanding my use of 5/16 tubing, or trying out 3/16 tubing while I do not have much 5/16 up yet. I have heard some pretty solid reviews of 3/16 tubing on this site, but I have a few concerns.

Matt

I have no experience with 3/16 but have pondered using it for the vacuum benefits. But regarding your few concerns, one of the things that I have heard from some on this site as well as from Bruce Bascom in person, is that some 3/16 tapers have quite a bit of trouble with 3/16 clogging after the first year or two. Especially at the T connections. That has turned me away from it, but I am small scale so I may do a experiment with it anyway. I should probably do that this year along with my list of 4739 other things to try.

If I were in your situation I would do a side by side comparison with the 3/16 leaving most of my taps as the 5/16 and see how the 3/16 performs in comparison over a period of at least 2 years preferably 3 or 4 years. As Dr. Tim would say you could probably overcome this problem with super sanitation and extra avoidance of wood chips from your tap holes into your 3/16 lines.

[FarmallCT]

It definitely sounds good if you have the drop. I talked with Bruce the other day and that was exactly what he was mentioning with the clogging. I believe he said he put up around 5,000 taps just to take them down a few years later due to clogging. Also I believe he mentioned not much additional benefit already being on a vacuum system. Definitely something I'd like to try, though currently just looking to get my order placed for material so I can get it in time to set up.

Will probably end up sticking with 5/16 since I already have some tubing and taps on hand, but it would be interesting to do as you suggested with a side by side comparison. Would be interesting to get a few taps and a little tubing to compare. Might be easier on a smaller scale with buckets or a small container to avoid two separate larger systems.

[Biz]

If you are on gravity, 3/16 is the way to go IMO. I have several short runs of 10-30 taps on 3/16" gravity, with elevation drop in the 10-20 ft range, and they all run well. On some lines I only see 10" of vacuum at the top. Two of the runs are on red maples and they produce nearly as much sap as the sugar maples. You need 30 ft or more drop to get maximum vacuum, but even a few ft of drop on 3/16 will increase sap production, provided the line isn't too long. I see very few clogging issues on my lines. You may not have clogging issues with 5/16" lines but won't get much natural vacuum if any.

Dave

[bmead]

My suggestion would be go with the 3/4 mainline and 5/16 tubing. with as little drop as your explaining 3/16 would not gain much vacuum and has been shown to have major clogging issues in future years. I installed a 1500 tap woods on 3/16 and removed all of it after the second season and the yield drop i saw.

As for tubing it self i prefer leader max grip for lateral lines and leader max flex for droplines. grip is a little more than uni50 however much easier to work with and holds in the woods better imo.

Taps i would switch to 5/16 vs 7/16 for tree health, the yield difference is minimal and the tree healing is much better!

Connecting 5/16 laterals to the mainline i prefer H20 saddles.

Mainline should have 2% or greater pitch, it can be run with less however it has to be absolutely perfect. if 2% is tough to get in your woods i would recommend going to a 1" mainline vs a 3/4



Hi All,


This will be my second year using tubing for maple syrup production. Last year I put up about 60 taps on Leader 5/16 semi rigid UNI-50 dark blue tubing straight into a 275 gallon tote. This year I am looking to expand to about 200 taps and add some 3/4" mainline.

I am currently stuck between expanding my use of 5/16 tubing, or trying out 3/16 tubing while I do not have much 5/16 up yet. I have heard some pretty solid reviews of 3/16 tubing on this site, but I have a few concerns.

My primarily concern is the need for a significant drop to create vacuum. I have read that a drop of approximately 20-30 feet is desirable to create sufficient vacuum. The area I am looking to tap does have a slight slope, but is mostly gradual with no major drops and could easily be traversed by an ATV/tractor if not for the trees/brush/rocks. Just judging by the eye, maybe a 10 ft drop over 200ft. That might still be a bit more than it actually is. Not sure how to accurately measure it better aside from running some lines and finding level.

I believe it is sufficient for a normal 5/16 gravity system, but am not sure that it would be enough to be worth a 3/16 system. The low point is next to a stream bed next to the road and is not near any current power source. A power post could be put in in the future for a vacuum system if I expand to the point it is desired, but is not readily available at this time.

Additional concerns include needing tools for 3/16 tubing where currently I have managed to put up 5/16 tubing by hand, as well as a discussion with a supplier regarding issues with 3/16 if not on a major slope or if vacuum is installed in the future.


My other main question has to do with tubing types. I started last year with Leader 5/16 semi rigid UNI-50 dark blue tubing, primarily due to it being the cheapest option and just wanting to get started with it. I used this in conjunction with CDL 7/16 spouts and CDL Max Flow Tees w/plug. What is the difference between the different tubing types? Rigid, semi rigid, max flow? I haven't found much describing each and their uses, especially company specific types. Should one type be used for laterals and the other for drops? Could also use some advice regarding differences between taps as well. 7/16, health spouts, antibacterial, check valves, etc. I am still fairly new at this and mostly self taught from reading this forum and watching videos of it being done.

Any other input regarding recommended lines, taps/differences between them, how to connect to the mainline, and mainline size/pitch would be greatly appreciated as well.


Thank you in advance!

Matt

[FarmallCT]

If you are on gravity, 3/16 is the way to go IMO. I have several short runs of 10-30 taps on 3/16" gravity, with elevation drop in the 10-20 ft range, and they all run well. On some lines I only see 10" of vacuum at the top. Two of the runs are on red maples and they produce nearly as much sap as the sugar maples. You need 30 ft or more drop to get maximum vacuum, but even a few ft of drop on 3/16 will increase sap production, provided the line isn't too long. I see very few clogging issues on my lines. You may not have clogging issues with 5/16" lines but won't get much natural vacuum if any.

Dave

At best I'd be lucky to get a 5, maybe 10 foot drop in a few places. Much of that would be reliant on tapping higher up on the tree than normal to achieve the necessary drop, and there would be minimal drop from the laterals to the mainline. Not sure if that would still be worth it. The 5/16 I had up last year flowed fairly steadily on its own with the current setup. Do you have any suggestions for creating a setup to compare production? I wouldn't mind getting some 3/16 to setup and compare, just not sure how to make a fair comparison and measure the difference.

Matt

[FarmallCT]

My suggestion would be go with the 3/4 mainline and 5/16 tubing. with as little drop as your explaining 3/16 would not gain much vacuum and has been shown to have major clogging issues in future years. I installed a 1500 tap woods on 3/16 and removed all of it after the second season and the yield drop i saw.

As for tubing it self i prefer leader max grip for lateral lines and leader max flex for droplines. grip is a little more than uni50 however much easier to work with and holds in the woods better imo.

Taps i would switch to 5/16 vs 7/16 for tree health, the yield difference is minimal and the tree healing is much better!

Connecting 5/16 laterals to the mainline i prefer H20 saddles.

Mainline should have 2% or greater pitch, it can be run with less however it has to be absolutely perfect. if 2% is tough to get in your woods i would recommend going to a 1" mainline vs a 3/4

Thank you, I am leaning towards sticking with that idea for the setup. I believe I should be able to get a 2-4% pitch on the mainline, at least in the section I plan to put up this year. Will have 200 taps max heading in the direction I am heading since it is uphill to the base of our small field and up the sides, with little to no expansion potential beyond the field other than the edges along the road. Wasn't sure if there was any major benefit between going up to 1" or if 3/4" would be sufficient in this spot due to the low number of potential taps. If I were to go further into the woods where there is more potential I would definitely go bigger.

Where do you get your lines/materials from? I used Bascoms last year and have not had any issues. I see the the Max Grip and Max Flex listed on the site so might try them out. Will definitely check out the 5/16 taps. Any suggestions between the green antibacterial, CDL white health, Leader tree saver, stuby with adapter, etc? Are any spouts for use with vacuum only so I can avoid them? I know seasonal spouts are an option as well, though not sure of the advantages/disadvantages on these either.

The one thing I have not been able to find on Bascom's site are the H2O mainline saddles you mentioned. Do you have a different supplier for these? I have seen several others on the Bascom site, not sure what the differences are with the different styles, or how some go together such as the full plastic wrap around vs stainless steel clamp, but was looking at the CDL stationary saddle or the saddle with the stainless clamp. Only thing I am unsure of is if they are complete or additional parts such as gaskets are sold separately.

Thank you again for all the help and advice!

Matt

[Sugar Bear]

It definitely sounds good if you have the drop. I talked with Bruce the other day and that was exactly what he was mentioning with the clogging. I believe he said he put up around 5,000 taps just to take them down a few years later due to clogging. Also I believe he mentioned not much additional benefit already being on a vacuum system. Definitely something I'd like to try, though currently just looking to get my order placed for material so I can get it in time to set up.

Will probably end up sticking with 5/16 since I already have some tubing and taps on hand, but it would be interesting to do as you suggested with a side by side comparison. Would be interesting to get a few taps and a little tubing to compare. Might be easier on a smaller scale with buckets or a small container to avoid two separate larger systems.

Comparing two different line size vacuum gravity systems is difficult. I think each size runs at capacity on different slopes and different numbers of taps. Figuring that out requires a level of science well beyond my pay grade.

[Biz]

It would be great to compare the two setups and prove which one works for your situation. Let us know results. For the 3/16 line I would do a line or two of no more than 25 or 30 taps, 200-300 ft max so you don’t get too much friction loss, and see how it does on a per tap basis. I use a 5/16 drop and checkvalve spout, and 3/16 lines elsewhere. You could put a gauge on the end of the line to check vacuum. Make sure the lines are cleaned well at the end of the season.


At best I'd be lucky to get a 5, maybe 10 foot drop in a few places. Much of that would be reliant on tapping higher up on the tree than normal to achieve the necessary drop, and there would be minimal drop from the laterals to the mainline. Not sure if that would still be worth it. The 5/16 I had up last year flowed fairly steadily on its own with the current setup. Do you have any suggestions for creating a setup to compare production? I wouldn't mind getting some 3/16 to setup and compare, just not sure how to make a fair comparison and measure the difference.

Matt

[DrTimPerkins]

Comparing two different line size vacuum gravity systems is difficult. I think each size runs at capacity on different slopes and different numbers of taps.

I'd second that. Getting good information isn't easy. Not saying that producer data isn't important, but doing one or two lines of one thing and a couple more of the other won't tell you much unless you control for tree size, position on slope, etc. In this case, you could actually see pretty decent vacuum on the upper trees, but still get low production due to the friction caused by the low slope section, so measuring vacuum alone isn't enough to tell the whole story.

[Sugar Bear]

My suggestion would be go with the 3/4 mainline and 5/16 tubing. with as little drop as your explaining 3/16 would not gain much vacuum and has been shown to have major clogging issues in future years. I installed a 1500 tap woods on 3/16 and removed all of it after the second season and the yield drop i saw.

As for tubing it self i prefer leader max grip for lateral lines and leader max flex for droplines. grip is a little more than uni50 however much easier to work with and holds in the woods better imo.

Taps i would switch to 5/16 vs 7/16 for tree health, the yield difference is minimal and the tree healing is much better!

Connecting 5/16 laterals to the mainline i prefer H20 saddles.

Mainline should have 2% or greater pitch, it can be run with less however it has to be absolutely perfect. if 2% is tough to get in your woods i would recommend going to a 1" mainline vs a 3/4

Good way to go IMO. I would add that you should make certain that your 5/16 have a decent length of undisturbed final run into the 3/4 mainline after the last tap of say 50 feet or more, as much as you possibly can. If you have a tree or trees down near the mainline and a long 5/16 line coming down from trees up higher, then do not tee into that 5/16 line from the down low tree. It will corrupt any flow/vacuum generated in the long 5/16 line coming from the upper trees.
If you have taps near the mainline they should be individually submitted to the mainline or with no more then two or three other taps from other low trees into the mainline.

In these off the grid vacuum setups, it seems to me a 3/4 or 1 inch mainline should be appropriately named a "lateral" line as it should slope down and across the slope "laterally". And any 5/16 lines should be called "vertical" or "vacuum" lines as they should run vertical down the slope as much as they can, synergizing slope and drop into vacuum and into the "lateral" mainline where in theory it should become vacuum less, unless of course you decide to vacuum the output of the mainline with a pump.

Your vacuum generation will take place only in the long 5/16 lines into the mainline so long as it is not corrupted by any T's inn the long final run into the mainline. Of course this is contingent on a decent amount of slope in your grove.

And it raises the question to me does it make sense to "vent" the end of a mainline in this scenario??? I would say yes, but I only have experience in this scenario by generating vacuum on 5/16" lines into barrels at the bottom of a run rather then a mainline. The good thing about this is it has shown what works well and what fails as I can see directly how much each run has generated and don't need a gauge to know if I am generating vacuum or not. Although this year I plan to use a gauge to see how much more vacuum I could be generating.

And YES you can generate beneficial vacuum in 5/16 if it is set up correctly.

Do not put more then 10 taps or less then 5 on a 5/16 vacuum run at peak flow times if they are big trees.

If they are small trees go 15 to 10.

[Sugar Bear]

After revisiting your landscape I would say that you should have no more the 4 or 5 taps on a 5/16 "vertical" line. The more of that 10 vertical feet that the final run into the mainline takes up from the last tap to the mainline, the better your 4 or 5 taps will do. You may at least be as good with taps to individual buckets.

If you do more then 4 or 5 taps on this landscape you will sap clog for sure and definitely be worse then taps with drops to individual buckets.

4 SURE!

[bmead]

Thank you, I am leaning towards sticking with that idea for the setup. I believe I should be able to get a 2-4% pitch on the mainline, at least in the section I plan to put up this year. Will have 200 taps max heading in the direction I am heading since it is uphill to the base of our small field and up the sides, with little to no expansion potential beyond the field other than the edges along the road. Wasn't sure if there was any major benefit between going up to 1" or if 3/4" would be sufficient in this spot due to the low number of potential taps. If I were to go further into the woods where there is more potential I would definitely go bigger.

Where do you get your lines/materials from? I used Bascoms last year and have not had any issues. I see the the Max Grip and Max Flex listed on the site so might try them out. Will definitely check out the 5/16 taps. Any suggestions between the green antibacterial, CDL white health, Leader tree saver, stuby with adapter, etc? Are any spouts for use with vacuum only so I can avoid them? I know seasonal spouts are an option as well, though not sure of the advantages/disadvantages on these either.

The one thing I have not been able to find on Bascom's site are the H2O mainline saddles you mentioned. Do you have a different supplier for these? I have seen several others on the Bascom site, not sure what the differences are with the different styles, or how some go together such as the full plastic wrap around vs stainless steel clamp, but was looking at the CDL stationary saddle or the saddle with the stainless clamp. Only thing I am unsure of is if they are complete or additional parts such as gaskets are sold separately.

Thank you again for all the help and advice!

Matt


If your expansion in future will run into the system your putting in now, be sure to size this system appropriately. If not 3/4 will likely work well.

I have a local dealer (Wendel's Maple) I work with for my materials, he carries leader, h2o and a bunch of other brands.

Taps wise I suggest leader check valve, either the stubby adapter style or the disposable/seasonal. Weather you go with the check valve or not I recommend replacing the tap each season. research shows huge yield improvement in both replacing taps and the use of check valve taps. the advantage being a clean, bacteria free tap and tap hole prevents the tree from walling off cells. Giving you better runs throughout the season and possibly a longer season and more sap.

I am not sure if Bascoms carries H20 products, their website has a dealer locator section to find a dealer near you.(https://h2oinnovation.net/en/)

The advantage with the h20 in my opinion is the gasket both seals the hole and a large are around the hole. The stainless clamp style (dsd brand) has a very small gasket and does not insert in the hole, making the seal iffy and them hard to get a perfect install on. I have seen this style fail in my woods, and i have since replaced them all.

I have not played with the cdl saddle at all, the h20 saddle wraps completely and is secured with a stainless screw instead of a plastic tab.

Never a problem!! if you have any questions feel free to reach out and ask!

Brandon Mead
D&B Maple

[bmead]

Good way to go IMO. I would add that you should make certain that your 5/16 have a decent length of undisturbed final run into the 3/4 mainline after the last tap of say 50 feet or more, as much as you possibly can. If you have a tree or trees down near the mainline and a long 5/16 line coming down from trees up higher, then do not tee into that 5/16 line from the down low tree. It will corrupt any flow/vacuum generated in the long 5/16 line coming from the upper trees.
If you have taps near the mainline they should be individually submitted to the mainline or with no more then two or three other taps from other low trees into the mainline.

In these off the grid vacuum setups, it seems to me a 3/4 or 1 inch mainline should be appropriately named a "lateral" line as it should slope down and across the slope "laterally". And any 5/16 lines should be called "vertical" or "vacuum" lines as they should run vertical down the slope as much as they can, synergizing slope and drop into vacuum and into the "lateral" mainline where in theory it should become vacuum less, unless of course you decide to vacuum the output of the mainline with a pump.

Your vacuum generation will take place only in the long 5/16 lines into the mainline so long as it is not corrupted by any T's inn the long final run into the mainline. Of course this is contingent on a decent amount of slope in your grove.

And it raises the question to me does it make sense to "vent" the end of a mainline in this scenario??? I would say yes, but I only have experience in this scenario by generating vacuum on 5/16" lines into barrels at the bottom of a run rather then a mainline. The good thing about this is it has shown what works well and what fails as I can see directly how much each run has generated and don't need a gauge to know if I am generating vacuum or not. Although this year I plan to use a gauge to see how much more vacuum I could be generating.

And YES you can generate beneficial vacuum in 5/16 if it is set up correctly.

Do not put more then 10 taps or less then 5 on a 5/16 vacuum run at peak flow times if they are big trees.

If they are small trees go 15 to 10.

The only thing i will add is not to vent the 5/16, this nulls any vacuum you are trying to create. It also allows bacteria into the system and the trees. studies have shown vented systems produce drastically less sap

[Sugar Bear]

The only thing i will add is not to vent the 5/16, this nulls any vacuum you are trying to create. It also allows bacteria into the system and the trees. studies have shown vented systems produce drastically less sap

Yes I agree but I was not suggesting to vent any 5/16 runs into the mainline which if he gets any vacuum at all in this landscape he will only get it formed from the final run of the 5/16 tubing into the 3/4 mainline. I don't think he will have enough slope to generate vacuum in the 3/4 mainline even if he does fill it with enough sap. And if he does fill the 3/4 mainline with sap I think he will be better off venting it with this pitch. I was suggesting he vent the 3/4 mainline so that if it proves too small at times of peak flow he could open the vent for peak flow and then shut it down again. Bacteria that gets into the 3/4 mainline should be a good distance from the taps and unless you plug the output of the 3/4 it will be there anyway. And even it you do plug the output of the 3/4 religiously between flow the bacteria will still get there anyway.

No definitely do not vent the tops of the 5/16 runs. That is different from what I am saying.

I think Wilmont has suggested venting in this situation but I am not certain of that.

Here ... read these two paragraphs from Tims article in 2013. He is spot on, but he should substitute the term "Vertical Line" where he uses the term "Lateral Line". You want these 5/16 lines to be Vertical down the slope as much as possible and not Lateral or across it. Call the mainline "Lateral" or slightly sloping. Its a non vacuum line. And could be vented to facilitate flow as Tim says. Anyway none of us are writers and that is why we have to learn a lot of this stuff on our own. Cause it makes for "intuitive confusion".

Tim Wilmont says the following .... pay careful attention to the last sentence of the second paragraph. That is the most important sentence in this thread

In contrast, a gravity line does not rely on air displacement; instead, vacuum is generated in each closed lateral line by the weight of the sap. In a gravity line that is leak free, the highest vacuum is at the top of each lateral line, and diminishes to nothing (atmospheric pressure) at the bottom where the line joins a mainline or empties into a tank. Thus trees lower along any line may be subject to some, but not the maximum possible vacuum, unless there is a significant amount of vertical drop on the line below the tree. For this reason, the ideal arrangement would be a line connecting trees near the top of a slope, and then a stretch of line below these trees continuing down the slope to the tank or mainline. This may not always be possible.

Although great diligence is necessary to keep spouts tight and lines leak free, the advantage of natural gravity vacuum is that each line is independent-unlike vacuum coming from a distant pump, the vacuum is generated in each individual line and a leak in one line does not affect other lines in the system. Mainlines should slope gradually in order to drain the sap into a tank, but mainlines in this system will not be under vacuum and could in fact be open at the far end in order to facilitate flow of sap down their length. Thus, in setting up a system, place the mainlines across the slope at a shallow angle, and run the lateral lines straight up the slope where they will generate the maximum vacuum due to elevation change.

[bmead]

Yes I agree but I was not suggesting to vent any 5/16 runs into the mainline which if he gets any vacuum at all in this landscape he will only get it formed from the final run of the 5/16 tubing into the 3/4 mainline. I don't think he will have enough slope to generate vacuum in the 3/4 mainline even if he does fill it with enough sap. And if he does fill the 3/4 mainline with sap I think he will be better off venting it with this pitch. I was suggesting he vent the 3/4 mainline so that if it proves too small at times of peak flow he could open the vent for peak flow and then shut it down again. Bacteria that gets into the 3/4 mainline should be a good distance from the taps and unless you plug the output of the 3/4 it will be there anyway. And even it you do plug the output of the 3/4 religiously between flow the bacteria will still get there anyway.

No definitely do not vent the tops of the 5/16 runs. That is different from what I am saying.

I think Wilmont has suggested venting in this situation but I am not certain of that.

Here ... read these two paragraphs from Tims article in 2013. He is spot on, but he should substitute the term "Vertical Line" where he uses the term "Lateral Line". You want these 5/16 lines to be Vertical down the slope as much as possible and not Lateral or across it. Call the mainline "Lateral" or slightly sloping. Its a non vacuum line. And could be vented to facilitate flow as Tim says. Anyway none of us are writers and that is why we have to learn a lot of this stuff on our own. Cause it makes for "intuitive confusion".

Tim Wilmont says the following .... pay careful attention to the last sentence of the second paragraph. That is the most important sentence in this thread

In contrast, a gravity line does not rely on air displacement; instead, vacuum is generated in each closed lateral line by the weight of the sap. In a gravity line that is leak free, the highest vacuum is at the top of each lateral line, and diminishes to nothing (atmospheric pressure) at the bottom where the line joins a mainline or empties into a tank. Thus trees lower along any line may be subject to some, but not the maximum possible vacuum, unless there is a significant amount of vertical drop on the line below the tree. For this reason, the ideal arrangement would be a line connecting trees near the top of a slope, and then a stretch of line below these trees continuing down the slope to the tank or mainline. This may not always be possible.

Although great diligence is necessary to keep spouts tight and lines leak free, the advantage of natural gravity vacuum is that each line is independent-unlike vacuum coming from a distant pump, the vacuum is generated in each individual line and a leak in one line does not affect other lines in the system. Mainlines should slope gradually in order to drain the sap into a tank, but mainlines in this system will not be under vacuum and could in fact be open at the far end in order to facilitate flow of sap down their length. Thus, in setting up a system, place the mainlines across the slope at a shallow angle, and run the lateral lines straight up the slope where they will generate the maximum vacuum due to elevation change.

I under stand the venting of the mainline on a gravity system. i just wanted to be sure your post was not miss interpreted to mean venting 5/16.

[DrTimPerkins]

As long as they are appropriately sized and sloped, mainlines don't really need to be vented. Doing so risks loss of sap if there is a freeze-up or other type of plugging somewhere along the line.