Drop Size on 3/16" tubing

[CaptT820]

Is there any empirical evidence showing whether or not a 5/16" drop to a 3/16" line yields more or less sap than a 3/16" drop to a 3/16" line?
I know there are several other factors involved such as elevation drop, number of taps, weather, etc. but wanted to ask.

I figured that a 3/16" drop to 3/16" line would yield higher vacuum thus higher sap yield, but this year is showing me otherwise, at least so far.

Thanks

[tgormley358]

My understanding from others here is 5/16 is preferred not for sap volume but to prevent the tree from sucking sap back into the tree when temps drop, like a reverse vacuum. I tried 5/16 drops on my 3/16 lines this year but haven’t concluded anything yet on its performance.

Tom

Tom

[ADK_XJ]

That's interesting, I'd never heard of this or thought through the possibility that it could draw sap back up into the tree...I'm ready for the Maple Research Center guy to show up and debunk this.

[CaptT820]

Tom-
I have seen this phenomenon myself this year where the sap either hangs out in the tubing or actually will run in reverse. I never saw this with the 5/16" drops. It would be nice to hear from Dr. Tim.

Thanks

[Wanabe1972]

This is the science to the check valve tap. It keeps the trees from sucking the sap back into the tree and causing the holes to close up. I have switched to 5/16 drops on 3/16 lines this year and can already see the sap does not fill the 5/16 drop so hopefully will protect the taphole. We will see.

[eustis22]

I assume there is some kind of transmogrified tee that takes a 5/16 drop to plug into a 3/16 lateral?

Can check valve spiles be re-used?

[Wanabe1972]

Yes you can buy the 3/16 x 5/16 x 3/16 tee anywhere you get 3/16 supplies.

[maple flats]

The 5/16 drop has less chance of having sap pulled back into the tree, because in 5/16 as it freezes the sap falls while the gases (air) gets pulled in. Unlike a 3/16 where the sap does not pass the air of vice versa.

[wnybassman]

My plan is to replace all my drops next year with 5/16ths.

[bmbmkr]

I assume there is some kind of transmogrified tee that takes a 5/16 drop to plug into a 3/16 lateral?

Can check valve spiles be re-used?

I quit buying CV spouts when I switched to 5/16 drops.

The most sap I have seen in the 5/16 drops is 14". That equates to 1.07 cubic inches. That would fill 38" of 3/16. the 3/16-5/16-3/16 tees are readily available and cheaper than CV spouts- win win.

[Goggleeye]

I thought I saw somewhere the research on whether to use 5/16 or 3/16 drops on 3/16 lines on gravity, but now I can’t find it. My average slope is 5-10%. I’m going to be replacing quite a bit of line this year, and I’m wanting to maximize production. Does anyone know where the article is? Or remember the best setup for this situation? Thanks

[AlbanyVT]

I have this same question about 5/16 drops on 3/16 line and don't see any research to support the practice one way or the other. I just did my fittings and tubing inventory this AM and am torn between which way to go when expanding my bush this winter. Anyone?

Thanks

[bill m]

You want to use 5/16 drops with 3/16 laterals. The reason is when the tree freezes at night it will suck sap back into the tap hole. This shuttling of sap in and out of the spout and tap hole causes bacteria to grow and sap production will go down. There is less of an effect with 5/16 versus 3/16 drops. Natural vacuum is not affected.