Surface installation does not require trenching and is so simple you can have an entire circuit up and running in one afternoon. By not burying the pipe, you avoid many of the usual municipal-code restrictions on location of a system and materials.
On the other hand, it is important to plan carefully so the exposed pipe is not too visible and runs through areas where there is no foot traffic. Often this means you’ll be running pipe in at least two sections: one line around the house to water foundation plantings and other nearby beds, and another line around the periphery of the lot to reach trees and shrubs planted there.
Because surface installations are often manual and connected to faucets, that type of hookup is discussed here. However, you can make a surface system automatic or hook it up as you would a subsurface installation.
Connecting to a Faucet
A proper faucet connection uses a series of connected valves that, in concert, control the system’s water pressure, filtering, and backflow prevention. If there are several outdoor faucets, it might be possible for each to supply one or two circuits that are turned off and on at the faucet. Usually, though, a single supply line is installed that leads from the water connection. Individual circuits are then turned on and off by shutoff valves located at the head of each circuit. This reduces the octopus-like assembly of pipes running from a single faucet.
Start with a dual shutoff Y-connector, with one outlet attached to the water connection and the other outlet left available. This is especially wise if the yard has only one outdoor faucet. If a second outdoor faucet is available, you could reserve it entirely for irrigation and use the Y-connector to assemble a second water connector for another part of the irrigation system, forming a simple two-circuit manifold.
Next you’ll need a backflow preventer. This is essential even if your municipal code does not mention it. For surface irrigation systems, a simple faucet-type antisiphon vacuum breaker is sufficient unless the local code states otherwise.
The filter is next in line. Some so-called complete drip irrigation kits don’t include one, but a filter is essential because the emitter outlets are so narrow that even the modern turbulent-flow emitters can be clogged by a few flakes of rust or other debris. Y-filters are the best choice, since they are both efficient and easy to clean. If you’re on a well system that might pick up sand, look for a sand-type Y-filter. T-filters can also be used.
The pressure regulator comes next. Although some manufacturers of pressure-compensating emitters and emitter lines claim their drip products can run at normal water pressure, it would be unfortunate to see the system blow apart if the pressure rose to abnormal levels. A pressure regulator will prevent that and also prolong the life of pipes and emitters by ensuring constant low pressure.
The simplest pressure-regulation device is the pressure-compensating flow control, which looks like a tiny washer. Better known and more efficient are preset pressure regulators. Buy one appropriate to the needs of the emitters you’ll be using: 15, 20, 25, and 30 psi are the most common. Be sure to install pressure regulators in the right direction; most casings have a stamped arrow indicating the direction of flow. Point the arrow in the direction of the irrigation system, not the house.
Because all the elements of the water connection are designed for 3/4-inch or 1-inch connections, finish with an adapter called a line connection, into which you can insert 1/2-inch solid supply pipe.
As you assemble the elements of a water connection, add lubricating tape or paste to each threaded fitting to ensure a good seat. You may also need one or two hose-to-thread adapters. (Pipe threads are more closely spaced than hose threads are, so trying to twist one onto the other could ruin both.) You might also encounter instances in which two devices meant to fit together in the series both have either male or female threads. If so, use an adapter.
Finish the water connection by solidifying it, if necessary, with metal or wooden stakes, and placing a 4- to 6-inch layer of gravel under its base to help absorb water resulting from flushing the filter.
Installing Supply Lines
Stake out the yard according to the plan, then lay out the main supply line from the water connection to the head of each circuit. The line will be less stiff and easier to manage if you let it sit in the sun first, but you’ll still probably need to hold it in place with a few wire stakes. Never stretch exposed poly pipe so it is completely taut. Leave room for expansion and contraction, especially in cold climates.
Poly pipe can be assembled using couplings, tees, or elbows (see Working With Vinyl Tubing). Unlike 3/4-inch or larger pipe, 1/2-inch poly pipe often uses compression fittings instead of ridged insert fittings with clamps. With insert fittings, the fitting is inserted into the pipe; with compression fittings, the pipe is inserted into the fitting. Simply push and twist until the pipe is inserted about 1 inch into the fitting; soak the end of the pipe in warm water first if it is too stiff. The fitting will cling to the poly pipe by compression, forming a perfect seat.
Begin assembling the supply lines. To link sections of pipe together, or at points where the main supply line branches or abruptly turns a corner, add a tee, elbow, or coupling. When you come to the head of a new circuit, add a manual shutoff valve (a ball valve, for example). This allows you to turn each circuit on and off separately. The shutoff valves should not be inserted into the main supply line itself unless it is the last circuit on the line; instead, insert the valves into a secondary section of supply line, because each circuit must be turned on and off independently from the others.
From the shutoff valve, add supply line as needed to reach the spot where the header line will be placed. Now turn on the water and flush. You are ready to install the circuit.