Beginners Guide: 1/4 Inch Distribution Tubing For Drip Irrigation
The thin tubes that snake from a drip line to each shrub and pot are the part of the system gardeners handle most. There is only one real choice to make about them, and one rule worth remembering.
Published 2 min read
A home drip system is built around a mainline, usually half-inch polyethylene, that carries water through the bed. From that line, quarter-inch distribution tubing, often called microtubing or spaghetti tubing, branches off to individual plants and ends in an emitter, a bubbler or a small sprayer. It lets one line feed plants at different distances.
Some quarter-inch tubing comes with emitters already built into the wall at regular intervals. Colorado State University Extension notes that spacings of 6, 12 or 24 inches are typical, which suits closely planted rows and containers. Plain tubing with a single emitter at the end suits plants spaced farther apart.
Polyethylene or vinyl
Polyethylene tubing feels stiff at first but handles sunlight and heat well. It does not soften and stretch in summer, so it stays tight on barbed fittings year after year. In hot, sunny climates it is the usual choice for tubing that lies on the surface.
Vinyl tubing is soft and flexible. It bends around tight corners without kinking. In strong heat it softens and can expand enough to slip off a barb, which is why it suits shaded beds, greenhouses and containers better than exposed ground.
Outside diameters are close to a quarter inch for both, though inside diameters differ slightly, and quarter-inch fittings generally accept either. Larger mainline sizes are less consistent, since manufacturers make half-inch tubing with different inside diameters, so buy mainline and its fittings from the same maker.
How long a run can be
Friction inside such a narrow tube reduces pressure along its length, and the plant at the far end gets less water than the one near the mainline. Manufacturers publish limits that vary, and a figure often quoted is no more than about 30 feet of tubing and 30 gallons per hour on a single run. Shorter is better. If plants are far from the mainline, move the mainline closer rather than stretching the tubing.
Installing it
Punch a hole in the mainline, push in a barbed connector, attach the tubing and run it to the plant. Pin it every couple of feet with wire stakes and cover it with mulch, which hides it, shades it from the sun and keeps it from becoming a trip hazard. If a plant is removed, seal the hole in the mainline with a small plug.
Every drip system also needs three pieces at the faucet or valve: a backflow preventer, which stops garden water from being drawn back into household plumbing, a filter, and a pressure regulator. Household pressure is often 50 to 70 psi, while drip parts are designed to run at roughly 20 to 30 psi. Without a filter, quarter-inch tubing and emitters clog; without a regulator, fittings pop apart.