Hi Spud

[Hop Kiln Road]

Didn't want to clutter up Starting Small's thread. My 300 taps are on 5 systems, none of which have easy access to electricity, obviously not ideal for vacuum systems. My 7 year gravity averages are 12.7 gpt sap and .325 gpt syrup. I am converting my 1/2" systems to 30p from black plastic basically for the interior visibility. This year hope to have one system of one tap per short lateral. My theory is 5/16 tubing can not handle peak flows and that stringing together 5 to 15 taps per gravity lateral, while it may produce some natural vacuum under some conditions, constricts the heavy runs which represents the bulk of the crop. This theory is based on two observations. First, my buckets always out produce my gravity tubing. Second, in the early tubing/natural vacuum studies, the 1/2" lines far out produced the 5/16, particularly during heavy runs in the lower slope areas. This information was sort of lost as it became irrelevant in the rush toward high vacuum. Bruce

[rchase]

I think the uvm proctor did research on 1/2" lat lines. From what i remember it producted alot of sap. Mabye Dr.Perkins can wieght in on this?

[cpmaple]

two season' s ago I had 47taps on gravity 5taps per lat running to a half inch main and was getting 65gals plus a day from them so I will stick with it but now they r on vac

[spud]

Hop kiln Road,

Your overall averages are very good for a gravity system. Getting .325 gpt of syrup per tap is not much less then what most high vac guys are shooting for. Most high vac people I talk to are very happy with a .4 gpt average. The studies on natural vacuum on gravity system were done using smaller tubing then 5/16. There are studies being done now using 1/2 tubing and custom made fittings that are not available to sugar makers yet. I talked to someone who has his whole woods set up like this and he said his first year produced 35+ gpt of sap. Although last year he only got 20 because of the short season. He is convinced he will get 35+ gpt of sap on average years. Please note though that he is using high vacuum to get this amount of sap. At this time they are not sure if this would be cost effective to set up a whole woods this way. I don't think by having 15 taps on a lateral line (gravity) would restrict sap flow. It seems to me the 5/16 tubing could handle that amount of sap (but maybe not if your trees run a lot). If your trees run well enough on buckets to out preform a tubing system with 15 taps then lowering the amount of taps per lateral line may be the logical answer. How far apart are your 5 systems? Could you put a booster tank in the middle of the 5 systems and then branch out to each system so vacuum could be used?

Spud

[Hop Kiln Road]

Hi Spud -

I pump 5 tanks on a 6 mile loop so it would be 5 gas vacuum systems which doesn't make economic sense. Just like vacuum systems need wet/dry lines, gravity systems need to separate the gas from the sap quickly to enhance flows. I have 260 taps on tubing and 25 buckets. I have a water meter on my gathering tank pump. It is during the peak flows that the buckets really outperform the lines.

My tree diameter is above average, I don't tap under 12" and double tap only at 24". This is really about capturing and concentrating sugar, not sap. Here is an old Morrow study:

http://fls.cals.cornell.edu/OCRPDF/FLS-014.pdf

My read of Table 5 is that unvented 1/2" lines on 3-7% (low) slopes had 2X the production of 5/16's during heavy flows. I understand that commercial operations have to have vacuum and all the studies ignored gravity systems since the 70's. But in semi-suburban sugaring it isn't necessarily a viable choice. I think I can reach an annual average of .4 gpt syrup on gravity systems, tapping fertilized orchard trees. In 2008, with excellent weather conditions, I got .42 gpt.

Thanks, Bruce