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Dr. Grainger's November 28th presentation PDF can be downloaded by clicking THIS LINK.  The PDF of his PowerPoint presentation is posted here to help those interested in protecting our water supply by implementing irrigation efficiency  techniques.  Protect our ever-decreasing water supply; irrigate responsibly.

Drip Irrigation

Drip irrigation is a low-pressure, low-volume lawn and garden watering system that delivers water to home landscapes using a drip, spray, or stream.  A drip irrigation system keeps roots moist, but not soaked, all while using less water than other irrigation techniques.

You can hide most of the drip irrigation parts under a layer of mulch, as long as you keep any parts that emit water on top of the mulch to prevent clogging. The system can also run on top of the soil or mulch, allowing the plants to conceal it as they grow and spread.

Drip Irrigation is the most efficient water and nutrient delivery system for gardening.  It delivers water, and even nutrients when they are added to the water source, directly to the plant’s root zone, in the right amounts, at the right time, so each plant gets exactly what it needs, when it needs it, to grow optimally. It enables gardeners to produce higher yields while saving on water as well as fertilizers.

With drip irrigation, gardeners are have:

  • Higher, consistent quality yields

  • Water savings: no evaporation, no run off, no waste

  • Uniform irrigation in any topography and soil type

  • Energy saving: it works on low water pressure

  • Efficient use of fertilizer and crop protection, with no leaching

  • Less dependency on weather irregularities

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Frequently Asked Questions: Drip Irrigation

We’ve compiled a list of some of the most frequently asked questions that we receive regarding drip irrigation.

  1. How does it work?  Water and nutrients are delivered across the garden or containers in pipes called ‘driplines’ featuring small units known as ‘drippers’. Each dripper emits drops containing water (and water soluble fertilizer if present), resulting in the uniform application of water and nutrients direct to each plant's root zone, across an entire garden.

  2. Why are drip systems better for plants? Crops need a consistent and balanced supply of water in order to grow.  Drip irrigation applies water and nutrients frequently and in small doses, ensuring optimal growing conditions that help produce the highest yields possible.  Here’s why plants are more productive with drip irrigation:

    1. High availability of water and nutrients

    2. Doses of water and nutrients tailored to plant’s development needs

    3. No saturation and good soil aeration

    4. Avoids high salinity caused by excessive fertilizer application

    5. No wetting of foliage that can result in fungal diseases

  3. What are the dripper effects in different soil types?  The soil is a storage room of the plants nutrients, and the medium, through which water and nutrients move.  It is the anchor for plants and the reservoir of water for plants’ growth.  There are various types of soil with differing characteristics, which determine what types of plants can be grown.  Nevertheless, plants can thrive in a very broad spectrum of soil textures when water is applied at the proper rate, with appropriate spacing.  Each type of soil creates a typical wetting pattern that will require a different layout.

    1. Sandy.  In sandy soil, the water will tend to go straight down, so we recommend using micro sprinklers or closely spaced, 12 in. apart, 1 GPH or 2 GPH drippers.

    2. Loamy.  In loamy soil, the water will move slowly and will spread evenly, so here you can use .5 GPH or 1 GPH drippers with a 16 in. to 18 in. spacing.

    3. Clay.  In clay soil in which drip irrigation work the best, the water will be absorbed very slowly, so use low flow drippers such as .5 or 1 GPH at a wider spacing, 18 in. to 24 in. apart.

  4. Does a drip tape work like a soaker hose?  Drip systems using drip tape are much more reliable and have a better controlled output than soaker hoses.  You can estimate 0.48 gallons per hour per 100 feet of drip tape or 0.00048 gallons per hour per drip emitter.

  5. Is a pressure regulator necessary to use with a drip system?  Yes, drip irrigation or low volume irrigation systems have been designed to operate with lower pressures than sprinkler systems, so pressure regulators typically are a necessity. Operating pressure suggested for a drip system is around 25 PSI with the lower pressure start at 15 PSI and the higher pressure is 30 PSI.  Using a pressure regulator will help to ensure your drip system will operate optimally.

  6. What are the pressure/flow requirements?  For flow systems providing 0.5 – 8 gallons per minute you'll need 25 psi to 35 psi.  You can calculate your flow rate by calculating how long it takes you to fill up a 5-gallon bucket (see the Drip System Components pdf - Click Here.)

  7. How big of a system can I run at a time?  For the main feeding lines you can roll out 100′ row using 1/2" mainline tubing.  Most hose bibs of normal pressure provide about 240 gallons of water per hour, so you can put up to 200 1-gallon drippers on that line.  Drip tape can go 250 feet of tape per 1 gallon of flow rate, so 8 gallons per minute = 2,000 feet

  8. Can I use it with a gravity-fed system?  Yes, if you can generate enough pressure, but normally you can't get enough head pressure.  You'd get 4.3 psi per 10 feet of elevation so you'd have to have a tank on a hill at least 35′ higher than the garden to get the minimum of 15 psi.  Most drip systems need 25 psi.

  9. How deep can the drip piping be buried?  You can bury the piping up to 6 inches max, however burying 2" to 3" inches is ideal for vegetables and instead of burying the lines with soil, it is best to just cover the lines with a good layer of mulch

  10. How do the drippers work?  Whoa, that requires several answers.  Drippers are the heart of any drip irrigation system  Drippers help to deliver the precise amount of water required to the plant’s root zone.  They are inexpensive, easy to install, reliable, and accurate.  They may be inserted directly into 1/2" poly tubing or extended to the plant with 1/4" microtubing.  Drippers incorporate three different characteristics: pressure compensating, adjustable flow, and turbulent flow drippers.

    1. Pressure Compensating Drippers are self-cleaning and utilize a silicone diaphragm, which moves up and down as pressure fluctuates to control the flow. The drippers are designed for long life under the harshest conditions.  Ideal use for a PC dripper is in any design when attention to the number of drippers and the total flow capacity of the drip tubing are not followed.

    2. Turbulent flow, or button drippers allow water to move rapidly in irregular random motions. Turbulent flow drippers regulate water flow by dissipating energy in friction against the walls of the water passage.  Button drippers are available in flow rates of .5, 1, and 2 GPH at 25 PSI and have extra large water passages to prevent clogging.

    3. Adjustable drippers allow the installer to change the flow for each individual plant. Twisting the dial on the dripper counter clockwise to increase or clockwise to decrease to adjust the flow between 1 GPH and 11 GPH.  These are difficult to maintain.

  11. Can I bury the drippers?  We recommend having the drippers or ¼" dripline above ground or covered by mulch to prevent clogging. The drippers should be installed above grade, and if necessary secured by a stake.

  12. Are the holes in the main 1/2" line pre-punched?  Can I punch holes in it?  Not in the main line.  You'll have to punch a hole and insert a fitting for the 1/4" delivery line.  However, drip tape is pre-punched and the standard emitter spacing is 12 inches

  13. Emitters up or down?  Up

  14. How many lines to run in a 4′ wide raised bed?  Generally, we run one line per row with 3 lines per 4′ bed if the bed is densely planted.

  15. How many drippers should be in a raised bed 1/2 of a 55-gallon barrel?  ​​​For plants like tomatoes, cucumbers, squash, or other large plants, use two drippers per 1/2 barrel planter

  16. Can drip tape be reused?  Yes, the 8 mil — 3-4 growing seasons and the 15 mil — several years

  17. Plant on top or to the side of drip tape?  You can do both!  For double row planting we like to plant to the sides

  18. What are the benefits of a drip irrigation system?  

    1. Minimal evaporation and overspray as well as lower water use for lower cost and better water conservation

    2. Direct connection to the hose spigot without the need to cut into the home water line

    3. Supply lines that can sit on the ground or under a layer of mulch, eliminating the trenches that underground systems require

    4. Flexibility as your plants grow and spread

    5. Customization for containers, raised beds, vegetable rows or shrubbery

    6. Exact delivery, preventing the distribution of water where it's not needed or where it can encourage weed growth

    7. Prevention of an overly moist environment that promotes fungal diseases

    8. Gentle, precise watering that minimizes runoff and erosion

  19. How long do you run it?  That's a tough one.  There are many variables – temperatures, soil type, crop, plant spacing, etc.  A general rule of thumb is whenever there is no rainfall, 1-2 hours every other day is sufficient

  20. What are the disadvantages of using a drip irrigation system?   A serious introduction to drip irrigation would be incomplete without a look at the disadvantages associated with its use:

    1. Drip irrigation should have a pressure regulator and filter to protect the drip system.

    2. The soft poly tubing can be susceptible to damage from insects, rodents, and household pets.

    3. A filter is required to guard against potential clogging at the very small orifices of the drippers and micro sprinklers.

    4. You cannot see a drip system working as you can a conventional sprinkler system.

    5. Drip irrigation creates a smaller wetted area, so control is more critical to avoid stress for the plants.

  21. How much will I save on my water bill by having a drip line system?   Drip irrigation systems emit water at a slower rate than above ground sprinklers or garden hoses.  Depending on the style and settings, drip emitters may apply water at 0.5 – 4 gallons per hour where a rotor style sprinkler can water between 1 – 6 gallons per minute.  Each garden will require different amounts of water since the total amount of water used depends on the size, shade, and plant selection.  But the slower application rate and higher efficiency of drip irrigation can reduce water usage by nearly 50%.

  22. Do drip irrigation systems need a back-flow valve?  If you are planning on distributing fertilizer through your drip irrigation system, a back-flow valve is necessary.  The back flow valve prevents fertilizer (or other non-potable contaminants) from flowing back into the main water supply and contaminating it in the event of  a loss of water pressure.

  23. Should I use a water timer?  You don't need to use a timer to operate a watering system, but for the additional low cost, it makes perfect sense.  Using a water timer turns your garden watering system into an automatic watering system.  This frees up your time for leisure and allows you to go away on holiday without having to rely on friends and family to water your garden.  It's worth the investment.

  24. How many drippers can I put on a drip line?  A limiting factor for how many drippers you can use on a single run of tubing is the GPH rating of the drippers themselves.  As an example, 1/2" tubing can supply 200 GPH in a single run, which means that one could put 400 .5 GPH drippers on a run of 1/2" tubing, or 200 1 GPH drippers, or 100 2 GPH drippers.

How long should I water my drip irrigation system?
Emitter type                    Length of each watering

High-flow emitter (Up to 20 gph) . . . . . . . . . . . . .

Low-flow emitter (Up to 4 gph) . . . . . . . . . . . . . . .

Low-flow emitter (Up to 2 gph) . . . . . . . . . . . . . . .

Low-flow emitter (Up to 1 gph) . . . . . . . . . . . . . . .

12 minutes

30 minutes

60 minutes

90 minutes

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