An irrigation line needs capping when the system requires modification, a section is being decommissioned, or a repair is necessary to isolate a leak. Capping is fundamental to maintaining system integrity and ensuring consistent water pressure throughout the network. Properly terminating a line prevents significant water loss, conserves water, and protects the surrounding landscape from flooding or soil erosion.
Essential Tools and Preparation
Before any work begins, the water supply to the specific zone or the entire irrigation system must be shut off at the main valve. After closing the valve, briefly run a zone or open a downstream faucet to relieve residual pressure in the line, preventing an unexpected spray when the pipe is cut. Tools needed include a sharp utility knife, dedicated pipe cutters for clean, square cuts, and a clean rag to dry pipe surfaces for secure sealing. Wear safety glasses to protect against flying debris or chemical splashes from primers and cements.
Sealing Smaller Diameter Drip Lines
Smaller, flexible polyethylene tubing, commonly found in drip systems, requires mechanical fittings that rely on friction and compression for a watertight seal. For main 1/2-inch poly tubing runs, the simplest method involves a figure-8 end clamp. This reusable device works by threading the tubing end through one loop, folding it over, and threading it back through the second loop to pinch the flow shut. Alternatively, a barbed end plug can be firmly inserted into the open end of the tubing, creating a secure, permanent seal against the interior wall.
For a more robust and reusable solution, installers can use an Easy Loc end cap, which features a barbed insert and a locking compression ring. To close off a small 1/4-inch emitter line or a hole where an emitter was removed, a small barbed fitting known as a “goof plug” is used. These plugs are pushed directly into the hole, where their barbed design creates an interference fit that holds fast against the plastic tubing wall. A low-cost, temporary technique for 1/2-inch tubing involves folding the end back several times and sliding a short, stiff piece of wider pipe over the fold to maintain the crimp.
Terminating Larger PVC Supply Pipes
Capping larger, rigid polyvinyl chloride (PVC) supply lines involves a solvent-welding process that creates a permanent, chemical bond between the pipe and the cap. The pipe must be cut cleanly and squarely, ideally with a ratchet-style PVC cutter or fine-toothed saw, to ensure maximum surface contact with the fitting. The cut end should then be deburred and cleaned to remove plastic shavings and prepare the surface for the chemical reaction.
The application of a colored primer, typically purple, is the first step; this liquid softens the PVC surface, preparing it to fuse with the cement. Immediately following the primer, a layer of solvent cement is applied to both the outside of the pipe and the inside of the slip cap. The cap is then pushed onto the pipe and held firmly for about 30 seconds to allow the initial bond to set, creating a single, leak-proof unit. If a sprinkler head is removed but the line remains active, the threaded riser beneath the head can be capped using a female-threaded plug or cap. This threaded connection requires a layer of polytetrafluoroethylene (PTFE) tape wrapped clockwise around the male threads to ensure a sealed connection under pressure.