Gauges on 3/16 lines

[Biz]

So over the past couple of seasons I have broken about half of the vacuum gauges that I have put on my 3/16" lines (with pump). They just stop working. Last week I took a gauge that works which I used last year. I shook it for a while and an amazing amount of sap came out which was obviously trapped in there from last year. My guess is sap gets trapped inside and freezes, destroying the gauge.

I also was observing the gauge while testing my Shurflo pump setup and the sap (or water for test) goes crazy when vacuum shuts off, goes shooting everywhere including in the gauges, where it can't escape. My plan for next season is to use 5/16" drops to the gauges instead of 3/16". This will at least allow the gauges to drain through the 5/16 where the 3/16" traps liquid and prevents draining. It will take a season to test this theory but worth a shot.

The other idea is to keep the pump running longer until sap stops flowing and vacuum is reduced, this should cut down on sap shooting around as much and make the gauges last longer. I'm testing my new controller which can sense vacuum and turn the pump off after vacuum drops instead of just when temp goes below freezing. For the small diaphragm pumps, the drop in vacuum indicates that sap has stopped or slowed down. This will optimize sap yield / battery life. Going to be fun to see how this works out, looking good so far. I'll post videos soon. Mick and David will be getting their new units next month to check out!

Dave

[SSS2017]

That's awesome Dave... I can't wait for the season!

[WVKeith]

Dave:

I just use natural vacuum with the 3/16" lines, but I also have a high percentage of gauge failures. I originally just credited that to cheap gauges, but I will watch for sap flow back this season.

Keith

[maple flats]

I had 1 gauge fail last year. My set up was using 5/16 take off from a 3/16 lateral. I had about 12 gauges out, with the 1 failure. When I run a gauge in a lateral I use a 5/16 about 28-36" long, with a 5/16 barb x 1/4" female iron pipe thread and the gauge screws onto that. I tie the gauge almost straight up from the lateral. That seems to work, but I usually still get 1 or 2 gauges fail each season. When I ran the gauges on 3/16 tubing the rate was higher.
My vacuum shuts off when I run out of gas. I try to guess when it will freeze and try to run an hour or 2 past, but it's still a guessing game.

[DrTimPerkins]

I also was observing the gauge while testing my Shurflo pump setup and the sap (or water for test) goes crazy when vacuum shuts off, goes shooting everywhere including in the gauges, where it can't escape. My plan for next season is to use 5/16" drops to the gauges instead of 3/16".

Gauge damage due to backflow isn't terribly uncommon, but happens more frequently with 3/16" tubing (drops) than with 5/16" due to the increased amount of backflow in the smaller diameter lines. Going to 5/16" drops will help some (reduced backflow), but will not totally eliminate the issue.

Most of these gauges have a small diaphragm. Liquid contacting this isn't an issue unless the liquid freezes and ruptures the membrane. Then the gauge is toast.

You can reduce the problem to a fair degree by putting a small check-valve in the line, or a water filter, or even a CV spout placed in line before the gauge. Just be sure the check valve is oriented in the right direction.

The other thing to keep in mind.....if this is happening to your gauges and causing them to fail, it is almost certainly happening in your tapholes as well and rendering them less productive in the second half of the season than they might otherwise be. Backflow carries microbes from the tubing system into the taphole, eliciting a tree response which results in the process of taphole "drying", which reduces sap flow from affected tapholes and depresses sap yield.