Mainline, consisting of flexible plastic ¾ inch and larger, carries sap from lateral lines to the collection point.  Mainline comes in a variety of colors and different 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 paint dark colored mainline white to maintain a lower temperature of the sap. 

The size of the mainline used depends on the slope and number of taps flowing from the lateral lines.  Although ½ inch mainline is manufactured, a minimum inside diameter of ¾ 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