vacuum level and weather conditions

[Buffalo Creek Sugar Camp]

Has anybody noticed vacuum levels change with different weather conditions? I have struggled to keep my two pumps above 20" all season. I have Indiana vacuum water cooled LR pumps. We have walked the lines many times trying to tighten things up. My systems seem tight because the sap is flowing steady into the releaser. But, twice during this season when it has been raining (low pressure system), my pumps have jumped up to 24 or 25". It was in the 40's so I know things weren't froze up somewhere. Is this typical with all vacuum setups? Or is it the type of pump I have? I do try to keep the pump cool, both cooling lines are running through small streams. My pumps should be big enough, 1.5 CFM per 100 taps.

[Haynes Forest Products]

I would say its a combination of Barometric pressure and the rain helping to seal the taps buy filling in the voids with liquid and bark swelling. Now it sounds like your starting to see patterns with the equipment, trees and weather. Write it down and learn from it and save the time in the bush with the knowledge.