Check Valve Adapters and Gravity

[Bill Southern NH]

I currently use the Leader Check Valve Adapters on my gravity tubing system and on my buckets as well. I have 60 taps on tubing, and 30 buckets hanging. I use the adapters because i was given a bag by a friend. I was wondering if there is a better spout out there for gravity systems or if the check valve adapters are fine. My lines and drops are all 2 years old. I'm also wondering if I should change the check valve adapters every year or try to disinfect them and use them over. My season is done and was just wondering for next year.

Thanks,

Bill

[CharlieVT]

The Proctor Gents may chime in with the best reply, but my understanding is that the data, while not strong, suggests that there is a benefit to using check valves on gravity. However, the benefit on a gravity system is no where near the benefit on a vacuum system.

As far as reusing them, not recommended. The plastic doesn't disinfect well, and reusing them will defeat the benefits.
HTH

[Russell Lampron]

Check valve adapters and spouts aren't needed with gravity because sap can't get sucked back into the tree when it stops running. Any adapter or spout will work with gravity as long as it is new if plastic or sanitized if metal.

[CharlieVT]

The subject of check valves on gravity has continuing interest for me.

From a cost effectiveness point of view, Russel is quite correct, check valves are not needed on gravity.
If you are buying spouts for gravity, stainless reusable, or plastic seasonal spouts make sense.

I don't think the statement: "...with gravity... sap can't get sucked back into the tree when it stops running." is entirely true. During freeze cycles, the negative pressure in the tree can draw sap back into the tree, expecially on a gravity tubing system; with traditional bucket and spile, not so much. But these tap holes on gravity are probably going to start healing up before a comparable tap hole with a check valve on vacuum.

Something that I don't believe has been studied, is the performance of a check valve in response to the slow and low pressure changes at the tap hole in a gravity system. Will the check valve ball close the valve in response to the slow pressure changes?

If you already have some check valves, no reason not to use them, and they may even improve sap yield by extending the duration that the tap hole yields sap.

From the article DEVELOPMENT AND TESTING OF THE CHECK-VALVE SPOUT ADAPTER
Maple Digest 21A:21-29 :

"2. Gravity Tubing or Systems with Low Vacuum Levels in the Woods. In general,
the higher the level of vacuum, the greater the potential benefit from Check-Valve spout
adapters. Although Check-Valve spout adapters may produce some improvement even
under gravity tubing conditions, the potential for backward movement of sap in tubing
systems is greater with increased vacuum level."

The entire article can be found here: http://www.uvm.edu/~pmrc/?Page=checkvalves.htm