Capping a drip line seals off a section of tubing to prevent water from escaping or redirects flow within a low-pressure irrigation system. This procedure ensures the system maintains proper water pressure and delivers water only where intended.
Termination is necessary for several reasons, including expanding the system to new garden beds, repairing broken tubing, or preparing the system for seasonal shutdown and draining. Proper sealing is important because water loss at the end of a line significantly reduces the pressure available for active emitters, compromising overall system efficiency.
Assessing Your Drip Line Components
Before attempting any termination or repair, correctly identify the type and size of the tubing involved, as capping methods are highly specific to the material dimensions. Drip systems utilize two main categories of poly tubing: the primary distribution line and micro-tubing.
The primary line, often referred to as the mainline, typically ranges from 1/2 inch to 5/8 inch in diameter, though larger sizes like 3/4 inch or 1 inch are used for high-flow systems. This larger tubing carries the main volume of water from the source to the designated watering areas.
Micro-tubing, on the other hand, is much smaller, usually 1/4 inch in diameter, and is used to branch off the mainline to deliver water directly to individual plants or emitters.
Note that the nominal size of poly tubing, especially 1/2 inch, can vary slightly depending on the manufacturer. Using compatible fittings is essential for achieving a secure, leak-free seal.
Terminating the Main Distribution Line
Terminating the end of the larger distribution line, typically 1/2-inch poly tubing, is accomplished using specialized fittings designed to withstand the system’s working pressure, which is usually regulated between 20 to 40 pounds per square inch (psi).
Compression End Caps
One common and secure method involves using a compression end cap, sometimes called a Perma-Loc fitting, which creates a tight seal around the outside diameter of the tubing. To install this, the end of the tubing is first cut cleanly and perpendicularly, and the locking nut on the fitting is backed off to expose the internal barb.
The tubing must be fully pushed over the barb and into the fitting’s body. Warming the poly tubing in the sun or warm water for about 15 minutes softens the material and increases its flexibility, making seating easier.
Once the tubing is seated, the locking nut is screwed forward over the tubing. This physically compresses the tubing against the barb to create a watertight connection resistant to water pressure.
Figure-8 Closures
A second, more economical method for terminating the mainline involves using a figure-8 closure, which does not require a separate fitting. This closure is a plastic piece with two parallel slots designed to fold and crimp the end of the tubing.
To use it, approximately six inches of the tubing end is inserted into one slot. Fold the tubing back on itself to create a tight kink, and then slide the folded end into the second slot.
This physical crimp stops the flow of water. This method is favored for its simplicity and allows easy draining for winterization, as the closure can be temporarily slid backward to release the water.
Sealing Micro-Tubing and Unused Emitter Holes
Sealing the smaller 1/4-inch micro-tubing or repairing holes in the mainline requires smaller, dedicated components to maintain a pressurized system.
Capping Micro-Tubing
When a run of 1/4-inch tubing is no longer needed, the line can be sealed using a 1/4-inch end cap or a small barbed plug. These small barbed fittings are pushed directly into the open end of the micro-tubing, effectively capping the flow with a simple friction fit.
Repairing Mainline Holes with Goof Plugs
Specialized components known as “goof plugs” or hole plugs are used for repairing accidental or unwanted holes in the main 1/2-inch distribution line. These barbed plastic pieces are inserted directly into the puncture site to restore the line’s integrity and prevent leaks.
Some goof plugs feature a different size on each end: a small side for standard 1/4-inch holes and a slightly larger side for a tighter seal in slightly stretched or damaged holes. Push the barbed end firmly into the hole until it sits flush with the exterior of the tubing.
This method is also used to seal the holes left behind when a 1/4-inch micro-tubing take-off is removed from the mainline. Using these plugs is essential for preserving the system’s uniform pressure.