long siphon

[springhills]

Does anyone have experience with a long siphon? I ran a 1" black plastic pipe 3000 feet from a collection tank to the sugar house. There's an 80 foot elevation gain and then a 120 foot drop. I was hoping to pump the sap until a siphon was primed, and then be able to shut off the pump, let gravity do the rest, and have the tube empty itself when finished. When we tried it for the first time It worked fine to pump through, but a siphon never got started and I had to let 80 gallons of sap back into the collection tank. We figured air must have gotten in to the line, but I started to wonder if the 40 foot net elevation drop was enough to overcome all the friction in that long pipe.

[Fred Henderson]

Although friction lose is much less in plastic than steel pipe. But with 3000 feet of it has to be considered and factored in. I can not tell you what it is. It has been a very long time since I had to calcaute them.

[RileySugarbush]

Siphons work by atmospheric pressure pushing the sap up the suction side of the tube when a vacuum is pulled by the weight of the sap on the down side. For sap, the maximum height on the suction side is theoretically about 33 feet, similar to water. For any significant flows, pressure loss due to friction will limit that a bit more. Probably not practical for more than a 20 or 25 foot rise above the level of the collecting tank.

[hydrogeo]

As a ballpark, my handy friction loss table shows a loss of about 23 feet per 1,000 feet of pipe at a flow rate of 5 gpm. This is with a c value of 120 for relatively smooth pipe. Without really crunching the numbers to see what the flow would be with 40 feet of head, it looks like in theory it would work, but your flow rate will probably be painfully slow. Interestingly, if you could up-size your pipe to 11/2" it looks like the friction loss would only be 2.83 feet per 1,000 feet of pipe at 5 gpm and it could work. However, I also agree with the amount of rise being a problem.

[maple flats]

I agree, you can not siphon over the 25-26-27' height. The same as pumps can not "pull over that height". The theoretical height at std air pressure is about 33' but that would only be for a perfect vac etc. You always loose. I don't know what you could do to correct it, without a series of sap ladders each with their own vac pump. Sounds too cost prohibitive.
Dave

[brookledge]

I would think that even if you could get it to pull a syphon you would lose it when the tank drained and then you would have to go back and pump it again to get it to work again so why not just pump it as needed.
Keith

[springhills]

Thanks for the replies. I guess I'm probably stuck pumping it at about 7 gallons a minute, and letting the 50 gallons run back. For now at least. I could get another 1000 feet of pipe; long enough to run around the hill. Any thoughts on this? I'd have to run it flat for about 2500 feet and then drop it the 40 feet in the last 1500 feet. It would be worth it if gravity would take it and the pipe would empty; even if I had to prime it with a pump daily. I don't need it to run fast, just to keep up with the gallon or two per minute rate in which it's flowing into the woods tank.

[WF MASON]

A friend of mine here in Porter has one of his collection tanks on the low side of a field , the field has a knoll in the middle , he runs a 3/4" line up and over the knoll to a holding tank by the road, I'm guessing the evelation from the tank to the top is 30-40', he pumps about 40 gallons to get the siphon going then it sucks the tank dry. I would think if you had pumped enough over the top the siphon would work most of the time , but I guess not.

[3% Solution]

Seven gallons is better than fooling with the thing right now
Are ALL you connections tight, if not that will stop any siphon.
Now if your going to pump it and you don't want that 50 gallons going back, put a check valve in at the tank.
Another problem you may have is the low point in your may have enough sap to freeze and not thaw out when you really need it to be.
Remember "Murphy's Law"

Dave