Should I change my drops when putting new seasonal spouts on my gravity lines?

[CharlieVT]

Reportedly, there is an article in the current Maple News with information about dropline replacement interval if you are NOT using CV adapters or spouts.

Has anyone read this who can briefly summarize the findings?

I'm getting ready to tap my gravity trees with new seasonal spouts. This will be my third year using these drop lines. Should I change just the spouts or drop lines and spouts?

Thanks in advance for your replies.

[mountainvan]

Short answer if you want more sap then yes.

[DrTimPerkins]

Has anyone read this who can briefly summarize the findings?

Having written that piece, the very short summary is:

1. If you're NOT using CV spouts or adapters, the estimated net profit is highest by replacing drops every 3 yrs.
2. If you can get/make/deploy drops very cheaply, your sap is worth a lot (you retail your syrup), or you have very high yields (0.5+ gal syrup/tap), then replacing drops more frequently might be advantageous. If the opposite is true (getting the drop material is at retail and/or you pay somebody to make and install them, your sap isn't worth a lot, or your have low yields of <0.3 gal syrup/tap), then replacing them less frequently (every 4-5 yrs) is more advantageous.
3. If you ARE using CV adapters or CV spouts, there is no economic advantage in replacing drops out to at least 10 yrs unless your tubing material or fittings are starting to fail.

Given that you are collecting sap using gravity, your baseline sap yields are likely to be on the lower side (compared to vacuum), thus replacing drops every 4-5 yrs is probably a better alternative. The lower your sap yields, the lower your "margin" for profit is as well, thus it is harder to justify the cost at a more frequent interval (even though as mountainvan has indicated, you definitely will get more sap). So it all depends....are you trying to just make more syrup, or are you trying to make more money? If you want more syrup, then change the drops. If you want to make more money, then change them next year or the following year.

Note that this is based upon the goal of achieving the highest estimated net profit, not the highest sap yield. A greater sap yield may be achieved by replacing drops every year, however the costs of doing that tend to be very high, so your net profit (what you put in your pocket after you pay all your bills) is lower doing that.

An Excel-based tool for assessing various sanitation scenarios can be found at http://www.uvm.edu/~pmrc/Economics%20of%20Replacement%20Strategies%20v.%201 1.25.2013.xlsx

[maplestudent]

Dr. Tim,

Though I always like to understand the science behind things like this, it was hard for a novice like me, when reading through the studies, to grasp the what the bottom line is due to all the variables. Thank you so much for simplifying it the way you have here.

[Homestead Maple]

A study that was done by Stephen Childs of Cornell University.

http://maple.dnr.cornell.edu/pubs/2013%20Maple%20Tubing%20Research%20Report.pdf