Drip irrigation can deliver efficient water use

Idaho — One of the most controversial issues in Idaho and throughout the arid west is water. Even with a wet winter with high snowfall, available water is limited. Homeowners caring for gardens and landscapes should be "water-wise," and one way they can do that is by using drip irrigation.

Drip irrigation allows for precisely-controlled application of water; it allows water to drip slowly near the plant roots through a network of valves, pipes, tubing and emitters. Drip irrigation may not be right for everyone, but it is a technique that can reduce labor and increase production using less water. It exceeds 90 percent efficiency, while sprinkler irrigation systems are 50 to 70 percent efficient. In many locations, water utilities exempt landscapes using drip irrigation during drought.

Drip irrigation helps maintain a desirable balance of air and water in the soil so plants grow better. Water is delivered more frequently at low flow rates, with the goal of only giving the plant the water it needs. Weed and disease problems can be reduced as soil in between rows stays dry. Drip irrigation creates an environment where desirable plants get the water they need to outcompete weeds for nutrients and sunlight.

A drip irrigation system consists of a backflow prevention device, a control valve to turn on and off the water, a filtration system, a pressure regulator, mainline and sub-mains, drip lines, drip emitters and air and vacuum release valves. All of these components can be found at an irrigation supply or hardware store.

However, not all components are needed in every landscape or garden system.

The backflow prevention device is required to prevent water from flowing back into the domestic water system after the water has been shut off. The law requires these devices on all home irrigation systems.

Control valves are often attached to a timer or irrigation control device. Alternatively, ball valves may be used so you can manually control the flow of water to each set of drip lines.

One of the biggest problems associated with drip irrigation is the clogging of emitters by small debris. To combat this, good filtration is necessary. Most drip systems use a simple screen filter that can be rinsed periodically.

Pressure regulators are needed when your water source produces pressures that are higher than what the drip system is designed for. Pressure regulators reduce the pressure to the drip line. Excessive pressure causes leaks and causes parts to blow apart.

Depending on the complexity of the system, a mainline and sub-mains can be used to distribute water to individual drip lines. Mainlines are generally made from PVC, while sub-mains and drip lines are made from polyethylene tubes.

Drip lines should be covered with mulch to get the most from the limited water being supplied. In addition, mulch helps keep the drip lines in place during windstorms. Drip lines have small openings at regular intervals, so they should be used in row plantings, where plants are also planted at regular intervals.

Emitters are water-dispensing devices that regulate the flow of water to the soil. They’re sold according to flow rates and typically come in one-half, one, two and four gph (gallons per minute) models. Emitters are one of the least expensive parts of the system but are one of the first to get clogged by debris. Emitters are used when plants are not found at regular intervals. Emitters can be installed to water hanging baskets, around shrubs, or anywhere drip lines will not supply sufficient water.

Air and vacuum release valves release air out of the system as it fills with water and allows air back into the system when the water is turned off. They should be placed at high points or ends of the system.

To set up a drip system, a backflow regulator is connected to the water supply, followed by the filter and then the mainline. Valves are installed at points where submains are installed. Each sub-main will supply water to drip lines in one zone. Drip lines are connected to the submain using T-connectors and run along the rows within planting beds. Emitters are installed on sub-mains to supply water to plants not being reached with the drip lines. The end of sub-mains and drip lines should have the air and vacuum release valves installed.

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