by Owen E. Dell
WHAT’S A DRIP IRRIGATION SYSTEM?
A drip irrigation system applies water slowly to the specific root zone of plants. This is accomplished with emitters that are placed at each plant and apply water drop by drop, allowing it to soak in to the soil rather than running off or blowing away. Black polyethylene tubing, placed above ground, carries the water from plant to plant. A valve, automatic or manual, controls the system. A backflow prevention device prevents water from flowing back into the pressure main and contaminating the potable water supply. A filter strains the junk out of the water so it doesn’t plug the emitters. A pressure regulator reduces the pressure to prevent the system from blowing apart. A valve (manual or automatic) controls the operation of the system. A pressure main supplies water to the system. If the system is automatic, a controller turns the valves on and off.
WHAT ARE THE ADVANTAGES OF A DRIP SYSTEM?
- Saves water
- Reduces weed growth
- Prevents runoff, puddling
- Encourages deep root system
- May be cheaper to install
WHAT ARE THE DISADVANTAGES?
- Not applicable to certain plantings (turf, ground covers)
- Fragile, easy to damage, subject to vandalism & rodent damage
- Requires frequent checking
- Emitters can plug up (bacterial iron)
DESIGNING A DRIP SYSTEM
- Evaluate the landscaping (kinds of plants, water needs, soil type, sun and shade areas, slopes and level changes)
- Evaluate the supply (well or meter, clean or dirty, pressure, volume)
- Locate point of connection, backflow location and type
- Lay system out in zones (sun & shade, high & low water-use plants, soil differences, slopes)
- Calculate the number of emitters needed per plant, per zone
- Determine whether to use drip tubing only or pipe manifolds
- Determine location of valves and pressure mains.
- Determine location and type of controller.
THINGS TO WATCH OUT FOR
1. Emitters need to be spaced more closely in sandy soils.
2. Filters are essential to preventing plugging of emitters.
3. Slopes present special design problems due to pressure changes.
4. Water in parts of Hope Ranch are not suitable for drip systems.
5. In most cases, backflow devices need to be higher than the emitters.
INSTALLING A NEW SYSTEM
1. Install pressure mains and control wires.
2. Install backflow devices, regulator, control valves.
3. Install controller.
4. Connect controller and valves to wires.
5. Connect pressure main to water supply.
6. Pressurize system and test for leaks.
7. Backfill and compact trenches.
8. Install plants.
9. Install drip tubing and emitters.
10. Flush lines and install end caps.
11. Test system.
12. Program controller.
RETROFITTING AN EXISTING SPRINKLER SYSTEM
1. Remove all sprinkler heads.
2. Cap all risers or disconnect the pipe at the valve.
3. Install a filter and a regulator at the valve.
4. Run drip tubing from the valve or connect to the old sprinkler pipe in the area to be watered.
5. Install emitters.
6. Reprogram the controller. (Install new controller if necessary)
-Prepared for Drought Awareness Workshop 1990
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