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Planning Your Drip Irrigation #3 - Locating Drippers
   

See the first of the series: Planning #1 - to Begin or the second of the series Planning Your Drip Irrigation #2 - the Drippers

This time, we are discussing the positioning of drippers for maximum effect.

Trees

If a tree is large enough to require more than one dripper, space the drippers around the tree on branch tubing so that the drippers are one-third the distance between the trunk and the outer drip line (the outer leaves). If on a slope, put the drippers on the uphill side.

Use 1/2" Tubing (T2100) for the branch tubing around a large tree and punch holes for drippers as required. You can also use 1/4" tubing (T3100) as a branch around a tree if necessary with 1/4" barbed tees (FB9) and drippers installed at the ends of the small tubing.

Bury

It's possible to bury drippers to avoid damage from mowers but a better idea is to clear the area around the tree and cover the drip irrigation mainline and the drippers with a loose clean mulch such as bark mulch or landscape stone. That reduces the possibility of dirt or mud leaking back into the drippers.

For all other plants that require only one dripper, place the dripper or the tubing extension from the dripper as close to the main stem as possible. That way, if there are any natural salts in your soil, they are pushed away from the root area by the drip irrigation water.

 

   

Use one sprayer to keep your compost pile damp

Driplines

Dripline is 1/2" Tubing with built-in drippers spaced evenly along the length (DL4100 or DL6200) . Place driplines as close to a row crop as possible. An easy way is to install the dripline first, and plant seed or transplants at each built-in dripper. If you have dripline with 12" spacing and if you need a higher rate of flow of water in sandy soil, consider installing a second dripline alongside the first but offset 6 " so that there is a dripper every 6 ".

The m aximum length of heavywall 1/2" Dripline (DL4100) in a circuit , with one-half gallon per hour drippers spaced every 12", is 400 feet, but keep any one continuous length of dripline at 250 feet or less. In other words, you could have three branches of dripline at 133 feet each or a length of dripline 220 feet long and another at 180 feet long. But you would not want any other drippers on the same circuit since we would be using our limit of 200 gallons per hour.

Compost pile

Keep your compost pile moist enough to speed the bacterial action by installing one half-circle sprayer (SP8) so that it wets the pile every time the drip circuit is turned on.

   
Hillsides

Drip irrigation is the only method of irrigation that is well suited to hillsides. Normal sprinklers create runoff and erosion but drip irrigation delivers water precisely to each plant and eliminates wasted water and eroded soil.

If the top of the slope is more than 10 feet higher than the source faucet, the best way to install the drip irrigation on a hillside is to run the 1/2" mainline tubing to the top of the slope to an air relief valve and then back down the slope with 1/2" Tubing branches running across the slope.

Caution - if the slope is higher than the source faucet, have a plumber install a backflow prevention device at the faucet to prevent irrigation water from backflowing into your water supply.

 

 

A flag dripper such as a D2 can be installed at the top of a hillside circuit as a mini air relief valve. Unlike some pressure-compensating drippers, it will drain and allow air into the system.

An air relief valve is needed at each high point, and 6" above the highest dripper, to let air into the system on shutdown and eliminate a vacuum that may suck dirt and mud into the drippers. Choose our OE17 Air Release/Vacuum Relief Valve for a large hillside drip system. A non-compensating dripper (our flag dripper D2) can be installed as a mini vacuum relief valve at the high point of a small hillside circuit.

Each dripper should be positioned slightly above each plant on a hillside. Gravity will pull the water slightly downhill right to the plant roots.

Always use pressure-compensating drippers on a hillside. See Planning #2. They deliver the same volume of water despite differences in water pressure common to hillside circuits.

   

Dripper extensions

You can use a hole punch to install a dripper anywhere along 1/2" Tubing. If the plant is away from the 1/2" Tubing, cut a length of 1/4" or 1/8" Tubing (T4100) to make an extension up to four feet long to reach the plant. The extension tubing is installed on the outlet of the dripper.

Use a stake to hold the end of the extension tubing above the soil so that dirt does not get into the tubing and so that the end of the extension stays in place at the crown or stem of the plant.

There is a lot of friction loss with 1/4" or 1/8" Tubing. Never use more than 100 feet of small tubing in any drip irrigation circuit. Plan on using 1/2" Tubing as much as possible to keep friction losses to a minimum.

Looping

Whenever possible, create a loop on a drip irrigation circuit. Loops on a circuit allow for more turbulent flow of water and cleaner tubing inside. If you have a circuit that supplies multiple branches across a hillside or along rows in a garden, add a return line on the far side of the garden or hillside to create a loop for better efficiency (see illustration above for an example).

 

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