Vacuum results are not what we thought

[MN Jake]

Wondering if anyone has ideas on this. We used bags 2011 up until 2016 at which point started up a vac system. Almost every year on bags we were getting full bags daily during the prime of the season. 3 years of vac now and we are pulling an average of a half gallon per the per day. All 3 years on vac have been like this. We have had no problem running 27" all the time on 500 taps. I'm just not understanding it.

[DrTimPerkins]

We have had no problem running 27" all the time on 500 taps. I'm just not understanding it.

Where are you measuring the 27"? Just to be certain, you are measuring that in " Hg (mercury)? What is the vacuum at the end of the mainline the furthest out in your woods? What sort of grade do you have? Single or dual-mains?

[MN Jake]

Thanks for responding Dr.
We are in a flat situation so ladders are one hurdle for us, they seem to work very well. I have not measured vac out at the ends but when I pull a tap on the ends it sounds very strong and leaves red marks on the skin in seconds. Slope is about 1% maybe 1.5 on some shorter runs. We are measuring in hg and that is at the releaser, we have a 100' 2" line feeding the vacuum to it. We oversized the pump for future expansion. It's a 5 hp two stage sihi, which I believe is 36 cfm at or above 20". I was under the impression that 15" is enough to double production.

[MN Jake]

Also I might add that I read Bills thread about the frost in Minnesota that you had responded to. I had thought maybe we were lacking because of it. These same 3 years have also been little to no snow cover at the coldest part of winter. After reading that thread I started to rethink the situation.

[S.S.S]

I have bags side by side with high vacuum, and if I had to rely on all bags I wouldn’t make half the syrup I do.

[MN Jake]

I have bags side by side with high vacuum, and if I had to rely on all bags I wouldn’t make half the syrup I do.
That's the impression that I had. I'm trying to figure out why its not happening

[Clinkis]

Something sounds amiss. I’m in a similar situation with minimal slope and multiple sap ladders. I’m using an old dairy pump and pull around 24” at the releaser and around 20”-22” in the woods. My average sap yeild increased 40%-50% when I switched from buckets.

My concerns would be pooling and inefficient ladders. I deal with these 2 issues constantly. I think the first thing you need to do is get some gauges in the woods at the ends of your mains. Sticking your finger on the end of tap will not tell you if you are having pooling. I constantly check vac levels especially below my ladders and if I see a significant drop I will adjust air injector and walk main looking for sags. Without gauges in the woods you are blind.

[n8hutch]

Are you tapping the same trees that you tapped on bags?
What is your tap hole sanitation like? Are you using new taps every year? CV taps ? 3/16 or 5/16 tubing? What size Drops are you using?
What kind of vacuum practices do you follow? Do you leave the pump on until things freeze up?
There could be lots of reasons. But you should be getting a lot more sap than that.

[BAP]

What’s your tapping depth?

[MN Jake]

What’s your tapping depth?
About 1 3/4". Did that with bags also

[eagle lake sugar]

I wouldn't beat yourself up over it, it has more to do with location than anything. Last season was bad here and this season is even worse. We're a couple hundred miles north of the majority of Vermont and Quebec producers and using their yields for guidelines are setting you up for disappointment. A sugar maker from Quebec started a 12000 tap sugarbush near me a while back, he ran it for a few years and discovered that extreme northern Maine is nothing like Quebec or Vermont. Those maples became saw logs and firewood and he moved back to Quebec.

[Russell Lampron]

Being on flat ground you will have to create an artificial slope to get good flow and vacuum transfer. On the end of the mainlines that are furthest away from the releaser secure your mainline as high in the end tree as you can reach so that you can get a 2% or better grade. You will have to have a reverse slope on the laterals on that end of the mainline. You won't get as much sap from them as you will the ones that are sloped down to the mainline but you will get some and more overall. If you can eliminate some of the sap ladders by doing that you can also set up a wet/dry set up to get better vacuum transfer to the lateral mains.

To touch on what someone else has said, every year since I put my taps on vacuum it has been a season saver or maker. When I did vacuum and buckets it was clear to see that I was getting a lot more sap from the vacuum. So much so that I hang zero buckets now which is how many I want to collect from.

[MN Jake]

Dr. Perkins was talking about frost on another thread that a fellow Minnesotan had started. That was my original thought behind our lower than expected yield. These last three years excavators were talking about 6 feet of frost in areas (I build homes). A couple years back waterlines were freezing 8 feet deep. I didn't really hear or ask for reports this winter but it was no different in terms of almost no snow cover, prolonged subzero temps, and frost that persisted throughout the maple season. I couldn't go 1 inch into the soil with a shovel until after the season ended. There's still frost in some areas.
Every year that our bags were filling was also good snows throughout winter and almost no frost.

Point is, I'm having trouble pinpointing a major problem with the lines. I'm a hands on type of guy and my vacuum "evidence" seems a little unscientific, if there is a loss it's not a significant amount of trees. Most lines are working well.

[maple flats]

If you have good vacuum at the end of your lines and keep leaks in check, you are getting the best you can expect with the conditions. Finishing the season and still not being able to put a shovel in more than an inch is telling the whole story. Just wait for a winter with average snow cover and you will see a huge gain, be ready for it. Under the conditions you described the bags would not have been near as good as the tubing/vacuum set up.
Try to add some vacuum gauges, I do it by using a saddle on mains and just a T on some laterals. Every main I have has a gauge at the far end, but maybe only about 5% of my 5/16 and about 10% of my 3/16 have gauges. However even that gives me a good picture of what is going on. I have sap ladders too, but plan to eliminate them this year and next. I will start using 3/16 to climb to the main instead because of the 3/16 fact that the air (gas) does not pass the sap.

[MN Jake]

Maple flats, the thread about the frost where Dr. Perkins mentioned the trees would not be able to recharge is where I started questioning things. It likely boils down to most were locked in the frost, there are a good number of trees that were likely thawed from the river edges. I should have spent more time examining which taps were really running and what weren't. Thanks everyone for your input