Irrigation 101

If you are considering operating and maintaining an irrigation system yourself, it is highly advisable to become familiar with the various parts of an irrigation system.

Water Meter

Read your meter before and after running your irrigation system to determine how much water is applied to your landscape. If you are interested in learning how much water is used for every minute your irrigation is running, note the time it takes for the meter to make one full rotation while running the irrigation system. If, for example, your meter reads in units of cubic feet and it took 30 seconds for the meter to make one full rotation, it is using 7.48 gallons (1 cubic foot) in 30 seconds and about 15 gallons per minute while the irrigation valve is operating. The water meter is generally located near the street and measures all water used at the residence. You can find out how much water an irrigation system uses and if the irrigation system has a leak by reading the water meter.

Water meter.

Anatomy of a Drip Irrigation System

This is a drip irrigation system for a home. There are several ways to combine essential components.

Irrigation Main Line

The pipe that comes from the water meter to the house is the main water line. An irrigation main line is a pipe that branches from the house main line in order to supply water throughout the irrigation system. This part of the system is under constant pressure. A manual valve must be inserted where the irrigation main line connects to the domestic main water line. This allows for the irrigation system to be turned off while making repairs to the system without an interruption of water to the house. The pipe that leads from the water meter to the house is the main water line.

Manual Valve

A manual valve is a device, operated by hand, that controls the flow of water through a pipe. It is commonly used to isolate and top the flow of water to one or more sections of an irrigation system during installation, maintenance, or while repairs are performed.

Electric Valve

An electric valve automatically opens when it receives an electric current through wires connected to the timer.  The valve closes when the current is off. Electric valves break the flow of water from the pressurized pipe (irrigation main line) to the non-pressurized pipes (lateral lines) of an irrigation system. Each valve allows water into an irrigation line when opened. Electric valves require 24volt ac.

Backflow Preventer

A backflow preventer is a valve that stops water from flowing ‘backwards’ from the irrigation system and back into the house, or domestic, water supply line.

Anti-siphon valves must be installed 6 inches above the highest emission devices (sprinkler, drip emitter, etc.) on each valve. A special backflow prevention device is required by code if the anti-siphon cannot be installed 6 inches above the highest emission device. Check with your local building department for any additional local requirements.

Filter

A filter prevents debris from entering an irrigation system.  Always use filters on drip irrigation systems. Most filters are sold separately. Some manufacturers sell units that consist of a valve, pressure regulator, and filter in one.

Pressure Regulator

A pressure regulator is a valve that provides a set or adjustable, water pressure to a system or line. Emission devices (sprinklers, drip emitters) operate best at different levels of water pressure. A pressure regulator on the entire system, or individual pressure reducing valves, may be needed to keep emission devices within an optimal operating range.  

Controller (Timer, Clock)

A controller is a device that is programmed to send electrical currents to automatic valves in order to turn them on at a pre-set time, for a specific length of time. They be mounted on an inside wall of the garage or outside near the irrigation valves. A controller that has a capacity for multiple programs is recommended. With multiple programs, irrigation valves can be individually scheduled (programmed) to meet the needs of specific water-use plant types.

Types of Controllers:

Traditional Controller

Smart Controller

Controller Terminology:

Multiple Independent Programs

An irrigation program allows for the setting of specific watering days. Having more than one program allows various valves to be set for different days. Ideally, a program will be capable of weekly (7 day) and interval programming. Weekly programming involves setting the watering days on certain named days of the week, such as every Monday, Wednesday, and/or Friday. Weekly programming is primarily used for lawn irrigation. Check with your city for watering restrictions.

Interval programming is a set number of days between irrigations. A controller that allows intervals of up to once every 30 days is preferable.    

Multiple Start Times

Smart controllers do not require setting multiple start times. If you are working with a traditional controller (not a smart-controller) it is best to set multiple start times to avoid run-off. Multiple start times allow the system to water more than once a day. For example, a controller with multiple start times can water the lawn for 5 minutes, turn off for 60 minutes, and turn on again to water an additional 5 minutes. Cycle watering allows the first irrigation water to soak into the soil (with little to no run off) before applying the second application. Clay or loamy soil, and sites with slopes, need multiple cycles.

Variable Run Times

The variable run time feature is not applicable to smart controllers. If you are working with a traditional controller (not a smart-controller) the variable run time feature allows for more precise watering.

Water Budgeting

Smart controllers will reduce the need to make adjustments using the water budget feature. Although they self adjust, it is always good to keep an eye on your plants to make sure the controller made a sufficient adjustment. If your plants look over watered or under watered, use the water budget feature to modify irrigation output.

Non-volatile Memory

Non-volatile memory retains the set program in the event of a power failure.

Battery back-up

Battery back-up will retain the set program and internal clock in the timer in the event of a power failure.

Rain Sensors Device Capability

This feature allows for installation of a device to automatically override the controller settings.  Some devices turn off the irrigation system during rain. Watering during periods of rain is a violation of Pasadena’s water waste ordinance.