Sap collection is the first and possibly the most important step in maple syrup production.
The sap collection and handling method dictates the quality of the finished product and the amount of profit earned. During the late 1950's, plastic tubing was invented to was sap collection. Research conducted in the first 20 years improved the performance and efficiency of tubing installations. Studies have also shown that plastic tubing will produce higher yields of cleaner sap than the traditional bucket method of collecting sap and greatly reduce the labor involved with sap collection. The following information, based on research and practical applications, provides the basic information and techniques recommended for installing a tubing system for the first time. It may also be used as a resource to upgrade your current tubing system with a more efficient layout. Remember, proper design, installation, and maintenance of a tubing system goes along with correct tapping procedures and sound sugarbush management.
Tubing has begun to take over the maple industry in Pennsylvania. Installation of tubing can reduce the time necessary to process maple sap into syrup. This publication will provide the basic for tubing installation. For additional instructions, consult your local Extension office, there is one in every corner of Pennsylvania and New York.
Prior to tubing installation a site evaluation of your sugarbush should be completed. Things to consider are the abundance and size of trees; the slope aspect and percent; and the distance to the collection point or tank. Tree diameter determines whether a tree should be tapped and how many taps should be used. Slope percent, the vertical rise over the horizontal distance, is useful for determining mainline size and tubing layout. Slope percent may be determined with a hand level, Abney, or clinometer. These inexpensive instruments may be purchased from Forestry Suppliers and will make the mainline layout more efficient.
Slope aspect, the compass direction a hillside faces, is important because it determines the microclimate of the sugarbush. The compass direction a slope faces determines the relative amount of sunlight, wind exposure, and length of time in snow cover the slope receives. South facing slopes are preferable for a sugarbush because they warm up earlier than north or east facing slopes. This allows for sap production earlier in the season, and facilitates faster thawing of tubing and mainlines earlier in the day. The distance to collection points or tanks, measured by pacing, calculates the amount of mainline required.
After these evaluations are completed, the next step is to map the sugarbush. Show the low and high points, roads, streams, direction of the slop, and the location of tree concentrations and the number of taps. The direction of slope, tree location, and the number of taps will help determine your mainline location, the amount of mainline and tubing required, the approximate number of tubing fittings needed, and the location and capacity of sap storage tanks.
Tubing system components
Mainline, consisting of flexible plastic 3/4 inch and larger, carries sap from lateral lines to the collection point. Mainline comes in a variety of colors and sizes to accommodate the number of taps flowing into it. Ideally, sap should stay cool in the mainline; therefore, many producers have found it helpful to pain dark colored mainline white to maintain a lower temperature of the sap.
The size of the mainline used depends on the slope and the number of taps flowing from the lateral lines. Although 1/2 inch mainline is manufactured, a minimum inside diameter of 3/4 inch is recommended. After years of use and research, the current trend is to use larger mainline diameters. It is much easier to expand an operation without changing the mainline, and larger sizes do not restrict the flow of sap. Larger mainlines also make sanitation during and at the end of the season easier and allow better vacuum transfer.
Lateral lines, consisting of 5/16 inch inside diameter flexible plastic, carry the sap from the trees to the mainline. Tubing for lateral lines also comes in a variety of colors, varying flexibility, and fitting designs. Layout and installation are basically the same for all brands. When the tubing is installed, proper fitting connections are vital. Loose connections may cause leaks in the system and may pull apart during colder weather. In recent years a semi-rigid tubing designed for permanent installation has been widely accepted for sap collection. The semi-rigid design reduces sag and friction thereby enhancing tubing system performance.
Fittings are used to connect the dropline, the section of 5/16 inch tubing connecting the spout (spile) to the lateral line, to the tubing system. Droplines should be at least 24 inches long to eliminate tree damage from cluster tapping. The number of droplines per tree is determined by the tree diameter.
To calculate the amount of tubing needed for your tubing system, a suggested rule of thumb is 15 feet per tap. For example, 100 taps would require approximately 1500 feet of 5/16 inch tubing. The number of fittings required corresponds with the number of taps in the system. For each tap, one spout and one tee are needed. Other fittings like connectors and caps will be necessary on a limited basis. Connectors should be used sparingly as they restrict the flow of sap in lateral lines, and tend to accumulate bacterial more readily.
After the type of vacuum system has been selected, tubing layout is the next step. This process may be accompanied by assistance from experienced tubing distributors, foresters, or Extension Educators.
The first step in tubing layout is to flag the proposed mainline locations in the sugarbush. Take into consideration the number and location of tappable sugar maples and the topography of the site. Mainlines may be located in a natural depression to facilitate sap flow from the lateral lines or run parallel with the slope of the sugarbush. Any brush or conifers that create shade of interfere with the mainline should be removed at this time.
Mainline should be supported every 50 feet by a tree or a support post. Ground lines are not recommended as they will be covered with snow, freeze quickly, and thaw more slowly. Maintenance of ground mainlines during the season is also more difficult and complete drainage is not guaranteed due to natural dips and low spots on the forest floor.
Using a hand level, flag the support trees at the point that indicates the grade and location of the mainline. Mainlines should maintain a slope drainage after every sap flow. A hand level is essential to maintain proper slope percent on hilly ground or flat terrain. On flat ground, a three percent slope is achieved by raising the end of the mainline three feet or more for every 100 feet of mainline.
The number of taps in the area dictates the size of the mainline. Today, maple producers and experienced tubing distributors are suggesting the use of larger mainline diameters. Although 1/2 inch mainline is available it is not recommended. A 3/4 inch to 1 inch mainline should have enough capacity to meet maximum sap flow requirements in a well designed system. Mainline sizes larger than 1 inch may be more difficult to sanitize when permanently installed in the sugarbush. Consult the following chart when considering the size of mainline required. (see table 1).
Table 1. Selecting mainline size (adapted from Morrow 1979)
|# of Taps|
|2000||1 1/4||1 1/4||1 1/4||1||1||1|
Although sap collection directly at the sugarhouse is ideal, it is often not possible. In this case, collection tanks should be located at natural depressions in the sugarbush that are easily accessible for pumping or transportation of the sap to the sugarhouse. Collection tanks should allow at least two gallons of sap storage for each taphole. More storage capacity will be needed at the sugarhouse. Several types of collection tanks are available. When acquiring used tanks, be sure they are clean, free of rust, and have not previously contained toxic materials. Place the tanks on strong level platforms or cribbing. Tank covers protect the sap from precipitation and debris and should be light colored and designed to allow ventilation to keep the sap cool.
Depending on whether the tubing system will use natural or artificial vacuum, lateral lines will vary in the number of taps they carry. While producers are using larger mainlines, they are also reducing the number of taps in lateral lines. Natural vacuum systems require more taps per lateral line to produce sufficient head pressure. It is important to remember that the number of taps per lateral line in a natural vacuum system depends on the slope percent.The slope of the lateral line must be a minimum of three to five percent. A practical maximum number of taps per lateral line is a natural vacuum system, based on the slope percent, ranges between 20-30 taps. Natural vacuum will only work in a tight, leak-free system. Sagging lateral lines restrict the flow of sap. The benefits of increased sap flow in natural vacuum systems are realized only during good sap flow periods.
The merits of vacuum pumping are several fold and should be considered over natural vacuum if at all possible. An artificial vacuum system requires a vacuum pump with a vacuum controller and a vacuum release unit. The vacuum pump is operated at all times when the air temperature is above freezing and there is potential for sap flow. Lateral lines in a artificial vacuum may have shallower slopes. Artificial vacuum is not a remedy for poorly designed or improperly installed tubing systems. A leak-free system substantially increase the volume of sap collected. The benefits of increased sap flow in artificial vacuum systems are found throughout the season, but are best realized during poor sap flow days.
Artificial vacuum systems do not pull or suck maple sap from the taphole; The process is more complex. Sap flow is generally initiated as temperatures rise above freezing. along with an associated increase in sap pressure within the tree. When tree pressure is greater than atmospheric or positive pressure, sap flows freely from the taphole. Conditions often exist during the production season when internal tree pressure is slightly below or equal to atmospheric pressure. This results in low volume or "weeping flows". Vacuum pumping, in effect, lowers the atmospheric pressure in the tubing system. This creates a pressure differential or positive pressure in the tree, which encourages sap to flow more freely. Research has shown more sap can be collected with an artificial vacuum with no significant reduction of sap sugar concentration.
Though the benefits of artificial vacuum are realized in a well designed and maintained tubing system, sometimes the distance from the sugarbush to the location of the vacuum pump is great. In this case, substantial vacuum is lost to friction. Vacuum-transfer systems or booster tanks can be used to reduce the loss of vacuum and increase the volume of sap collected by moving the source of the vacuum closer to the trees. In a vacuum-transfer system, a second tank is placed in the sugarbush. Mainlines from the second tank serve different parts of the sugarbush. The transfer tank is connected to the vacuum pump by two lines. One line carries that sap, while the other evacuates gases, therefore creating a vacuum. The distance between the vacuum-transfer tank and the vacuum pump determines the effectiveness of the system. Distances less than 600 feel may only show slight advantages. Where trees are 1200 feet or more from the vacuum pump, the transfer system is more effective.
Mainlines may be suspended in 9-gauge steel wire or stretched and hung by wire cable grips at each end. Mainlines suspended by wire offers much more support than cable grips and offers a more permanent installation. Mainlines are installed in locations that were flagged earlier. The support wire should be installed as straight and tight as possible, at a minimum of three percent slope. The wire may be attached to the support trees or posts using a lighter grade wire at intervals of no more than 50 feet. The lighter wire will break in the event of wind damage and is easier to repair than the 9-gauge support wire. Side pull the support wire to support tree with the lighter wire. Where wire is attached to a living tree for support, a section of hose, tubing or wood block should be used to protect the tree and allow it room to grow.
The mainline support wire may be tightened using a come-along or hand winch. Electric fence tighteners can be sued for this purpose and left in place.
After the wire is installed and attached to the support trees or posts unroll the mainline underneath the tightened support wire. Mainline should be tied to the support wire with wire twist ties, plastic ties, or short lengths of stainless steel wire approximately one foot apart.
Mainline is best installed with the temperature between 30 and 50 degrees F. If installed in cold weather, the mainline will sag during warmer sap season temperatures. if installed in warm weather, the mainline will contract in cold temperatures and may separate at the fittings.
After the mainline is installed, the lateral lines may be hung.
You may wish to carry a bundle of pre-made droplines to ease installation of the lateral lines. A dropline consists of a long piece of tubing, at least 24 inches to reach the tappable circumference of the tree, a spout, and a 5/16 inch tee.
Start at the mainline with a roll of 5/16 inch tubing and weave it around tappable trees. It is important to roll out the tubing in a manner to avoid twisting and kinking. Avoid sharp bends around trees with rough bark. This might distort the tubing and reduce sap flow. The number of taps per lateral lines suggested by experienced tubing distributors and most maple producers is 10 to 15 taps. This number depends on the type of vacuum system used as discussed previously. When using natural vacuum, plan ahead for the possibility of expanding into an artificial vacuum system in the future. Therefore, keep the number of taps per line at a minimum.
Make the lateral lines as straight and tight as possible. Avoid branching lines off each other with the use of additional tee and y fittings. Branching lines are more difficult to sanitize during and after the sap season, and may lead to less efficient flow of sap. Use a hand level to establish minimum lateral line slope requirements. A special tee fitting may be used to create a harness around the last tree on a lateral line. This eliminates the need for a nail in the tree as support. Lay out other lateral lines in the same manner. Try to bring several lateral lines to common points in the mainline to reduce the number of fittings and breaks in the mainline. Cap unused inlets on mainline fittings.
Lateral lines may stay up for one or two days until the droplines are added.
To install the droplines in the laterals a tubing installation tool may be used, which cuts and spreads the lateral line and inserts the tee from the dropline. As an alternative, a pair of vice grips, tubing spreaders, and shears may be used. A thermos of hot water may replace the use of tubing spreaders. Do not use your mouth for warming the tubing. This introduces bacteria into the system. Note that semi-rigid walled tubing should not be spread to insert the dropline tee or other fittings. The number of droplines at each tree is determined by the tree diameter. Nails, preferably aluminum, in the tee of the dropline may be used as support, but this should be kept to a minimum by letting the trees support the tubing.
Tools for installing the mainline
The following is a list of tools and fittings used to install the mainline
- Mainfolds - used where lateral lines join the mainline
- Stainless steel clamps - to tighten mainline around the fittings
- Reducing connectors - for areas where two different sized mainlines are used
- Wire ties or plastic ties - to attach the mainline to the support wire
- Cable grips - used in the place of support wire
- Nail apron or tool box
- Come-along or hand winch - to tighten the support wire
- Screw drive or nut driver - for clamps
- Pruning shears - for cutting mainline
- Wire cutters and pliers
- Hand level
- Propane torch or thermos of hot water - to heat the mainline before putting on fittings
Tools to install lateral lines
Installation tools and fittings include:
- Hand level
- Shears or pruners
- Apron to carry tools and fittings
- 5/16 inch tee's
- Caps to plug unused fittings
- 5/16 inch connectors
If your tubing installation is not permanent and will be taken down at the end of each sap season, a coding system needs to be devised to identify trees with their corresponding tubing lines. This may be done a number of ways and should include a mark on the tree as well as a tag on the tubing line.
Tubing systems should be checked after tapping and before the first sap flow for possible trees missed during tapping, system damage, and disconnected lines. Systems should be checked also during the season after heavy snowfall, high winds, or extended periods of non-sap flow. This can be accomplished by walking the area for a visual check. Leaks can be found best during sap flow. Artificial vacuum helps locate leaks either by noticeable air bubbles in tubing during a flow or by a hissing sound. The use of an inexpensive vacuum gauge to determine the level of vacuum at the tap is very useful. Natural vacuum can be used to locate leaks, but only during a strong sap flow when natural vacuum is developed.
Hollow taps, avoided during tapping if possible, and tubing holes caused by animal damage should also be located. Damaged tubing should be repaired immediately in anticipation of the next flow. When performing this task, an inexpensive vacuum gauge helps locate areas of low vacuum indicating the presence of leaks. Research has shown that a vacuum of about 15 inches of mercury at the taphole is optimal. This level if vacuum at the tap warrants 20 to 25 inches of mercury at the vacuum pump.
Mainlines should also be checked annually at the support trees. Make sure the tree is not growing around side pull wire and the wire is in good condition. Follow tubing system maintenance procedures throughout the sap season.
Tubing that is removed annually can be washed in place before removal or after it is removed from the woods.
Using this reel-type tubing washer, coils of tubing are place in a spool and slowly rotated in a tank of cleaning solution. Open spouts, tees and tubing ends pick up the solution, and the constant rotation moves the solution through the lines. The solution is removed by rotating the spool out of the cleaning solution. This process may take 30 minutes or more for each step. A practical maximum size for the roll or tubing is around 50 taps. This allows the solution to move freely through the roll and is easily maneuverable by the operator.
Producers with larger operations may prefer to allow the tubing to remain in place during the off-season. Permanent installations require a method of pumping a cleaning solution through the system. This can be accomplished with a pump and tank. A state of the art unit, such as an air injection pump, which uses air pressure with a cleaning liquid, is well suited where liquid must be pumped over long distances or up steep hillsides.
Nearly all producers leave mainlines in place permanently and pump cleaning solution through them. One should either pump clean water through the mainlines after using a cleaning solution or allow sap to flush out the cleaning fluid at the beginning of the next sap season. After cleaning mainlines, open ends of the pipe should be sealed with tape or a fine screen. This reduced the risk of nest-building insects or rodents contaminating and plugging the pipe during the off-season.
A common cleaning solution used in the tube washing device and pressure washing system is a chlorine solution. By mixing 1 part unscented chlorine bleach with 20 parts clean water, you can effectively sanitize the tubing system. A triple rinse with clean water is recommended to remove any residue from the cleaning solution. It is suggested that the chlorine salt residue attracts rodents that ultimately will chew on the tubing. For this reason, producers have used an alternative cleaning solution that does not contain sodium, or simply water alone. In any case, never use a household detergent or any other soap to clean maple tubing or any other equipment used in the maple operation. Soaps cannot be completely rinsed away and will destroy the maple flavor and aroma of syrup.
Uihlein Tubing Washer
A simple but effective device for washing tubing can be constructed easily. This device permits lateral lines to be rolled up in the woods, washed, and drained without being unbundled. The materials may be obtained at little to no cost. These include:
Small electric motor, 1725 r/min, 1/4 hp, with a 2 inch V-belt pulley
Bicycle wheel (20 inch) used as a pulley on a reel shaft
Double pulley from an electric clothes dryer
Washing tank - stock-watering tanks work well for this purpose
Tubing systems in the sugarbush greatly increase the amount of sap collected when they are designed and maintained properly. The use of artificial vacuum also increases sap collection. These are not a substitute for proper tapping techniques and sound sugarbush management. In turn, quality control of the entire maple operation produces the finest maple product possible. The information provided here is intended to help you make maple sap production more rewarding and less labor-intensive work. Please remember, in all aspects of maple production, always practice safely.