Check valves on 3/16th tubing

[CharlieVT]

Has this been discussed? If so, someone point me to the thread?

Excluding a discussion of cost, and restricting the discussion only to sap yield, doesn't it make sense to use a check valve on a 3/16th where good vacuum is being generated?

I am considering using a CV2 spile with a short length of 5/16th and a 5/16th to 3/16th coupler to adapt the CV2 to a 3/16th system.
(Or are check valves for 3/15th tubing already in the works by one of the manufacturers?)

Why would this not provide the tap hole longevity benefits that are seen with conventional pump vacuum systems?

Thanks in advance for your thoughts.

[Cedar Eater]

Has this been discussed? If so, someone point me to the thread?

Excluding a discussion of cost, and restricting the discussion only to sap yield, doesn't it make sense to use a check valve on a 3/16th where good vacuum is being generated?

I am considering using a CV2 spile with a short length of 5/16th and a 5/16th to 3/16th coupler to adapt the CV2 to a 3/16th system.
(Or are check valves for 3/15th tubing already in the works by one of the manufacturers?)

Why would this not provide the tap hole longevity benefits that are seen with conventional pump vacuum systems?

Thanks in advance for your thoughts.

Is this a 3/16 pump vacuum system or a natural vacuum system? My understanding is that 3/16" natural vacuum lines do not experience the surges common on mechanical vacuum systems.

[maple flats]

Someone stated in another thread, that a CV in 3/16 made no sense because the vacuum is always on until everything freezes solid and it is back up before the trees thaw.

[DrTimPerkins]

Someone stated in another thread, that a CV in 3/16" made no sense because the vacuum is always on until everything freezes solid and it is back up before the trees thaw.

Although there hasn't been a lot of research on this subject, there are certainly some scenarios where backflow could occur (leaks, freeze-ups), although probably with less frequency than on a pumped vacuum 5/16" tubing system. These would not be from the mechanical releaser dumps, unless the 3/16" tubing were in combination with a pumped vacuum system. On a hybrid (pumped vacuum +3/16") system, when you do lose vacuum, the backflow could be WAY more than on a 5/16" system, simply due to the smaller size/volume of the line. And the small surges from releaser dumps will flow further back for the same reason. So there is no simple clear-cut answer to this question.....in some cases the CV with 3/16" will definitely help, more so in hybrid systems than in pure 3/16" gravity vacuum systems.

The 3/16" guru Tim Wilmot just stopped by my office while I was typing, so I asked him. His answer was "yes", CVs can help in a 3/16" vacuum system. He did do some 3/16" tubing research with CVs several years ago, and felt that they were beneficial.

[220 maple]

Dr. Tim
Pass the word to Tim that the 3/16 tubing systems that he lead the Workshops on in West Virginia last June worked beyond belief, one of the participants reported over 15 gpt, I was skeptical myself because the trees that I chose for the test had very little drop until they fell over the edge of the ridge, I will send him video via email later, needless to say he said it would work and he was right! In my personal opinion he is a first ballot Maple Hall a Famer, if he is not already in the Hall of Fame .
Mark 220 Maple
President WVMSPA

[CharlieVT]

Thanks, Gents, for the replies.

From the Wilmot paper, Maples Under Pressure 2009
"...the negative pressure measured at the tap hole can be as low as -7.5psi (15 inches of Mercury)."

From the Wilmot paper, The 3/16th Phenomenon Maple News December 2014:

"...if the tubing runs down a slope that is 20’ from top to bottom, and the tube is full of sap, the weight of the 20’ of sap is theoretically enough
to create 17.7” Hg... When the taphole is lower than this, for example when the taphole in question is in the middle of the line and is only 10’ in elevation from the bottom, then the maximum vacuum at that taphole will be less—10’ of sap will pull a maximum possible vacuum on that taphole of about 8.8” Hg."

More thoughts: Since these values are theoretical, and in practice due to variables like leakage, gravity induced vacuum will be lower, I find it easy to imagine that trees lower on the slope of a 3/16th gravity line could easily have negative pressures in the tap hole that exceed the vacuum in the lateral. Given this, and the data on the benefits of check valves, I theorize that check values would be especially valuable on trees that are lower on the slope of a 3/16th gravity line.

While there may be little benefit from a check value for the trees at the highest elevation of a 3/16th gravity line, I am thinking it may be possible to devise a "rule of thumb" where by any trees below a certain minimum elevation above the bottom of the 3/16th line would most benefit from a check valve spout.

[DrTimPerkins]

Dr. Tim
Pass the word to Tim that the 3/16 tubing systems that he lead the Workshops on in West Virginia last June worked beyond belief, ....

I will let him know, and I'm sure he will appreciate the kind words. Thank you.

[M&M Maple Grove]

Thanks, Gents, for the replies.

From the Wilmot paper, Maples Under Pressure 2009
"...the negative pressure measured at the tap hole can be as low as -7.5psi (15 inches of Mercury)."

From the Wilmot paper, The 3/16th Phenomenon Maple News December 2014:

"...if the tubing runs down a slope that is 20’ from top to bottom, and the tube is full of sap, the weight of the 20’ of sap is theoretically enough
to create 17.7” Hg... When the taphole is lower than this, for example when the taphole in question is in the middle of the line and is only 10’ in elevation from the bottom, then the maximum vacuum at that taphole will be less—10’ of sap will pull a maximum possible vacuum on that taphole of about 8.8” Hg."

More thoughts: Since these values are theoretical, and in practice due to variables like leakage, gravity induced vacuum will be lower, I find it easy to imagine that trees lower on the slope of a 3/16th gravity line could easily have negative pressures in the tap hole that exceed the vacuum in the lateral. Given this, and the data on the benefits of check valves, I theorize that check values would be especially valuable on trees that are lower on the slope of a 3/16th gravity line.

While there may be little benefit from a check value for the trees at the highest elevation of a 3/16th gravity line, I am thinking it may be possible to devise a "rule of thumb" where by any trees below a certain minimum elevation above the bottom of the 3/16th line would most benefit from a check valve spout.

I am a one-man operation so I am trying a new approach this year of finishing up early and spending a portion of the season on research and development, hence my latest frequency of posts.

I believe I heard UVM is in the works of some research at the moment on 3/16 lines but I was curious if any of this information has been updated in regards to check valves on 3/16. I run a highbred natural gravity/diaphragm pump system and use 5/16 drops with clear spouts. We have had our first solid freeze in weeks so I walked my lines to see what was happening. All of the taps had at least 6 to 8 inches of distance between the tap and the column of sap. This also includes taps below the laterals.

In addition, I have a shut off valve right before the pump so I can clean out the strainer without losing vacuum in the lines so theoretically, no microbes backing up at that time.

Would there be any other reason of switching over to check valves other than an additional safety net? Am I missing something? I realize at 300 taps you’re talking about a difference of $75 but when you get to thousands, it quickly adds up.

[billyinvt]

I have been using check valve spouts on 5/16 drops into 3/16 laterals on about 200 taps for a few years now. All natural vac, no mechanical. CDL makes a T that accommodates this set up. It works really well. I have used stainless spouts in the past and I get better total yield with check valves. My guess is that it has to do with the longer viability of the tap hole due to the check valve keeping it "cleaner". I think it is worth the extra cost, but I'm also not trying to do it on a large scale.

[DrTimPerkins]

https://mapleresearch.org/pub/1219tubing-2/

Research has shown that 3/16" tubing tends to outperform 5/16" tubing for the first year, is about the same for year 2, and is less for yr 3 onward without some type of sanitation effort. This is with new spouts each year and no line cleaning. Mainly this is due to clogging at fittings. Films of microbes forming on the inside of the tubing break off, slowing down the flow of sap or plugging sap flow at fittings entirely. So clogging is ONE of TWO issues.

The SECOND issue is sanitation. Backflow of sap (carrying microbes into the taphole) can occur in 3/16" tubing systems, and especially on hybrid (pump + natural vacuum) systems it can be way worse than in 5/16" systems. The smaller tubing diameter allows backflow to occur from a much longer section of tubing.

Sanitation is as important in 3/16" tubing as it in in 5/16" tubing, however there are some key differences. The main one is that NO method of spout/dropline sanitation by spout/drop replacement is completely effective in combating clogging further down the line at unions or other tees that aren't replaced. Thus, either some type of chemical sanitation OR total replacement of all fittings (tees and unions) every couple of years is necessary to maintain good yields on 3/16" tubing in the long run.

Cornell has also done similar research and unsurprisingly has found similar results. I think the Southern maple group is also finding similar results. In short, 3/16" can be very effective in generating vacuum, but it takes slightly different approaches (more work) to maintain good sap yields.

To return to the question of CVs...yes, they work well in 3/16" systems at the spout sanitation level, but they don't address the clogging issue (same as new spouts, new drops, antimicrobial spouts, etc.). None of those things have any effect on clogging.

[DRoseum]

I use (and replace annually) check valve spiles on 3/16 drops/laterals on aquatec and shurflo vacuum setups. Very very happy with them. One other possible benefit is preventing backflow when tapping below the lateral line. Tapping below lateral on vac systems (or nat vac if you have adequate slope/setup) is effective and can increase tapping band on a tree. The check valve seems like it would be more effective because you could not get the air gap (which is what prevents the backflow) using 5/16 drop lines.

Tapping below lateral might be necessary or desired due to various factors.... prior over tapping.... height of latteral....

[ToadHill]

Dr. Tim, I know that you've recommended dropline replacement every 3 seasons to optimize yields and I was wondering about the timing of the dropline replacement. Specifically, can it be done at the end of the season while pulling the old taps or is there a risk of contamination between then and the next season? Would it be better to replace them in the fall or winter? Thanks in advance for your reply.

[M&M Maple Grove]

Thanks Doc. for the updated research, and everyone else’s input. I’ve been swapping out new t’s, drops and spouts(are t’s assumed with drops?) annually or every other on average. i’m always stocked with drops in the woods and if I see something I don’t like, I switch it out. Looking for a balance between new material and best sanitation practices. I typically get in early and end my season on the early side to combat sanitation issues as well so check valves may have a much less return on investment for someone that follows the same practices.

The first raw oyster I find jamming up my vacuum strainer is when I’m out. I’d rather deal with the headaches during freeze ups.

I viewed the above article and to my understanding, this study consisted of 3/16 lines and 3/16 drops. Is there any current data on 3/16 with 5/16 drops?

Another consideration is what actually happens to the circumference of the interior diameter of the tubing over time as it is being stretched out from tees being swapped out and the weight of long tree to tree runs?

Quick note on sanitation. This year, I added a small, above ground cartridge filter before the vacuum dumps into my holding tank. It is gravity fed and did a fantastic job of keeping the microbes down in the tank. Here’s a quick video I made if you would like a visual:

https://youtube.com/watch?v=TjKy3UthAds&feature=share


This one shows a technique on how to clean the shurflo strainer without losing vacuum and creating backflow:

https://youtube.com/watch?v=OtgRVHPCQmY&feature=share