5/16" Gravity runs - open top or no?

[tuolumne]

We have installed 4 new gravity lines on 5/16. These have between 18 and 24 taps each, with elevation changes of 30-40'. Runs are all around 300-350' long. I feel that more taps would be better to achieve some gravity vacuum, but none of the runs could be combined. The runs are all sealed; the end of the line is a tap. Last night we observed a steady drip at all collection points, and air pockets slowly moving uphill. Based on how fast our buckets were dripping, it seemed like there should be a lot more sap coming out. Of course, removing the top tap causes all the sap in the line to rush out at once.

What is the consensus on these numbers? Should the top be opened or not? I did add a vacuum gage to the top of one line last night, but things are frozen now and we won't have any results in yet. When I cut the line to tee in the vacuum at the top, there was a tremendous sucking of air for a few seconds, so there was some vacuum. It was too late to watch it build again.

[5050racing]

Closed it will build vacuum and keep bacteria to minimum .I'm just a small time others will chime in and confirm this,I have 4 runs like yours maybe not as long I have some 1/2" mainline that it goes into.

[Sugarmaker]

We have good luck with a CLOSED system.
Regards,
Chris

[tuolumne]

We'll leave things closed at this time. The sap is running about 1.5 gal./hour from a line with 24 taps and the vacuum gauge still reads zero. The buckets seem to be having a better run than that.

[Maplesapper]

A vacuum wont exist if air is allowed to enter. Think hamster water bottle.
If you have a proper vacuum, the bubbles would be pulled down the tube where they overcome the atmospheric pressure at the bottom of the lateral.
The Dr at UVM seemed to prefer a good free fall with no taps for the last portion of the run.
Also the vacuum is stronger at the bottom of the run in natural systems vs pumped.

[lastwoodsman]

I also have had good luck with a closed system.

[SeanD]

A vacuum wont exist if air is allowed to enter. Think hamster water bottle.
If you have a proper vacuum, the bubbles would be pulled down the tube where they overcome the atmospheric pressure at the bottom of the lateral.
The Dr at UVM seemed to prefer a good free fall with no taps for the last portion of the run.
Also the vacuum is stronger at the bottom of the run in natural systems vs pumped.

I have 30 taps on 5/16" gravity that I've used for four seasons and I have a new one with 30 this year. In both cases the air bubbles go down hill. I used to think something was wrong, but I can never find leaks and I get a decent amount of sap.

The closed system will give you a bit of natural vacuum and keep microbes out.

Sean

[Ryan August]

I know this is talking open vs closed but I wonder the same. I have full lines that just do not seem to move much. Any ideas hoe much volumn a foot of 5/16 holds?

[wnybassman]

Online chart said .0045 gallons

http://www.engineeringtoolbox.com/pipe-water-content-volume-weight-d_1734.html

[wildlifewarrior]

Think hamster water bottle.
We have had 30-40 taps on a gravity system the last two years the same as was described, 5/16ths going into a 1 inch mainline with saddles. We haven't had any luck, for instance today on 25 taps we got about a gallon TOTAL! our buckets got about 1/4 of a gallon each. We look at the system and I cannot help but think that the problem is like you mentioned the hamster bottle effect. We notice that the sap seems to build up at the fittings I feel that there isn't enough pressure from the trees to break the pressure at the fittings consistently.
I am glad I am not the only one experiencing this.
We decided to put a main line wire in today to ensure that there is no dips.

Thanks
Mike

[Maplesapper]

Hey Warrior-
The guys at VMU only spoke of achieving Vacuum in 5/16 with a minimum of 25 taps, and a straight run of tubing, ending in a steep pitch.
This ONLY on only single laterals running down the slope.
How far do you laterals run before they hit the mainline?
Is the mainline open?

[wildlifewarrior]

Hi, I don't want to derail the thread or change the focus on me.
We have no more than 8 taps per lateral, each lateral about 30 feet long at the most and most have a 10 deg drop. We were told many times to not exceed 10 taps per lateral, 25 seems like a ton. Any ideas would be greatly accepted.

Thanks
Mike

[Maplesapper]

Here's part of what the Dr. at UVM said.....http://www.uvm.edu/~pmrc/highvacuum.pdf

While the maximum number of taps to put on a 3/16" line is yet to be
determined, I have had success with lines up to 22 taps during strong sap
runs... under these conditions the sap flows very rapidly through
the line, and because of this may arrive cooler at the tank than in a pumped
line.
• For high vacuum, the minimum number of taps to place on a 3/16" line
approximately 150' long is 4 or perhaps even less; the minimum number of
taps on a similar 5/16" line is as yet undetermined, but is greater than 10. This
assumes a good vertical drop below most of the trees.
• A long zig zag line has achieved better vacuum and flow in my experiments
compared to a branched.• Line length does not seem to be very important.

[wildlifewarrior]

Thanks Maplesapper, apparently more is better!
Mike

[Yellzee]

it's hard to give into the temptation for the instant visual happiness of seeing sap flowing out by opening the end of a lateral. I run all gravity and in my experience over the long term keeping the end closed yields more sap, and as others have mentioned,,, it will keep bacteria out and your tap holes will last longer. maybe you need to have a decent drop though. if you are doing small individual runs to a bucket, don't be afraid to run the lateral further down hill to collect if you have the drop to use. ie.. you don't have to put the collection bucket at the last maple tree... more natural vacuum.

[tuolumne]

I was maybe to quick to draw conclusions at the first based on visual observation of sap flow. Our total run over Saturday and Sunday for 434 taps was 275 gallons or 0.63 gallons/tap. 102 of those taps are on gravity lines, and the rest are on buckets. We collected all gravity lines in 5 gallon pails and had a total of 94 gallons. That means that this first run was 0.92 gallons/tap for the gravity lines and 0.55 gallons per tap on the buckets. These totals show a much different picture than my visual observation of the dripping. That said, the gage stayed at zero the whole time.

I am sold on the 3/16 idea even having never tried it. Our sugar bush seems ideal for an extensive gravity system of 3/16" laterals running into large/open mainline collectors. If fittings and such become more readily available in the next few years it will help.

[Maplesapper]

Natural gravity vacuum systems have almost zero vacuum at the top of the lateral.....as you are finding.
Greatest vacuum is created at the end of the lateral, all the weight of the collected sap compounding the effect closer to the end of the run.
Try the gauge at the bottom.

[Bentley Wood Maple]

We'll leave things closed at this time. The sap is running about 1.5 gal./hour from a line with 24 taps and the vacuum gauge still reads zero. The buckets seem to be having a better run than that.
We started with 180 buckets and quickly learned how time intensive emptying buckets is not condusive to working 60 hrs a week to subsidize the sugarhouse.
Initialy I thought per tap buckets out yielded our gravity taps. But after 4 yrs of learning gravity lines I think we have closed the gap on per tap yield. Up to 375 taps and and last yr we came close close to one qt syrup per tap on forest trees. The upper ends of all 6 of our mainlines are either capped or have a 1/4 turn ball valve

[Snowy Pass Maple]

I was maybe to quick to draw conclusions at the first based on visual observation of sap flow. Our total run over Saturday and Sunday for 434 taps was 275 gallons or 0.63 gallons/tap. 102 of those taps are on gravity lines, and the rest are on buckets. We collected all gravity lines in 5 gallon pails and had a total of 94 gallons. That means that this first run was 0.92 gallons/tap for the gravity lines and 0.55 gallons per tap on the buckets. These totals show a much different picture than my visual observation of the dripping. That said, the gage stayed at zero the whole time.

I am sold on the 3/16 idea even having never tried it. Our sugar bush seems ideal for an extensive gravity system of 3/16" laterals running into large/open mainline collectors. If fittings and such become more readily available in the next few years it will help.

Call D&G USA in VT - they have 3/16 "maple" tubing and fittings now - they are putting another roll in the mail for us tomorrow! Can't wait to try it... going to take advantage of the cold snap to get them up this coming weekend. Great to deal with as others have commented on here.