Yet another 3/16 thread

[tonka]

So of all the info I have consumed on and off the trader about 3/16 tubing layouts, it seems like what I've all read is on the lines of high vacuum, steep slop, and vertical drops to gain high vacuum levels in the system. Is it possible to have a system work with no intention of trying to reach high vacuum levels in a system with the recomended 10 to 15 taps on slight slope of 3% to 5% with no vertical drop but to have a tail from the first tap on the line to your mainline or tank that is 30+ feet in length keeping the same slope throughout to create a column of sap in the line that will create some vacuum in the line?

I have seen it myself work on a 5/16ths gravity system and it did create natural vacuum on a 3% to 5% slope.

[maple maniac65]

When I first started 20 years ago, I ran 500' of 5/16 with 110 taps on it. The experts laughed and told me I was doing it all wrong.

Well I've been wrong most of my life but it amazes me that the so called mistakes get no credit unless a fancy college degree comes with it.

[wnybassman]

I think some vacuum will be achieved. I believe I read the general rule of thumb is 1" of vacuum for every 1 foot of drop.

[maple flats]

I believe the vacuum generated will be about .85"/ft drop or there abouts when sap is flowing good and somewhat less on slow flows. The more sap in the 3/16 the greater the vacuum.
Somehow if I'm picturing your set up question right, I think a tail from the last back down to the main will be counter productive. It seems that would pull sap from the main if it was full enough, using the sap in the line generated from the first line going past all the taps until you achieved a balance and then the vacuum might be equal in both directions, if it picked up no sap from the main, it would be like venting the top tap, which kills any vacuum.
The property of vacuum generation using 3/16 is that the sap does not pass the gases (bubbles) in the line.
While you were able to get what looked like good flow with 500' of 5/16 and 110 taps, you were getting less than what a vacuum pump could have because you were over loading the line and line friction held it back some.
Others have posted similar results in the past on 5/16 too, but just do an experiment. Connect a pump to push water thru a 500' roll of 5/16 and measure the flow for a minute, then do the same using 50 or 75' of 5/16 and measure again. The difference is due to line friction.
Heck, even when using air hoses to power a higher consumption air tool, you lose from line friction if the air line is too long.
Back to your question, at 3-5% slope you can generate vacuum on 3/16 even without the ideal 30' drop in elevation and in that case, longer is better as long as you do not exceed about 30-35 taps on the line (one study by, yes the college degree) Tim Wilmott suggested that 37 might be the max, I have 41 on one line that is 1200' long, I'll be changing that to 2 lines for this next season. And I have about 30' drop in the lower 60-70'.
With 3% slope if only 200' long (total 6' drop) you might get somewhere near 5" at the top and progressively less as you go down the line, if that line is 500' you should get 2.5 times that at the top, then less as you go downhill. If the drop was an average of 5% the vacuum increases proportionally.

[tonka]

When I talk about a tail, my thinking on it is if you can build up a column of sap in the line with the proper amount of taps with the subtle slope, the column of sap would help create vacuum, the more sap (from good run) the more weight there is pulling and you would gain in slope drop that would create more inches of vacuum and the same vacuum at all taps because the majority of the weight of the column is below the lowest/first tap on the line.

That clears it up when you say .85"/1 foot slope drop is created, I assumed that occurred when you have vertical drop. That's my miss understanding.

[Thompson's Tree Farm]

So of all the info I have consumed on and off the trader about 3/16 tubing layouts, it seems like what I've all read is on the lines of high vacuum, steep slop, and vertical drops to gain high vacuum levels in the system. Is it possible to have a system work with no intention of trying to reach high vacuum levels in a system with the recomended 10 to 15 taps on slight slope of 3% to 5% with no vertical drop but to have a tail from the first tap on the line to your mainline or tank that is 30+ feet in length keeping the same slope throughout to create a column of sap in the line that will create some vacuum in the line?

I have seen it myself work on a 5/16ths gravity system and it did create natural vacuum on a 3% to 5% slope.
The key is the amount of drop not the steepness of slope

[tonka]

Thanks for all the input, you have all help me understand more on the subject of 3/16 tubing layouts. Very helpfull, yhanks again!