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