If you are replacing or putting in a newlawn or perennial bed, subsurface dripirrigation has many advantages oversprinklers in certain situations and maybe right for your needs. It's a robusttechnology that has proven reliableeven in the harshest conditions. Toavoid damage to the underground linesfrom replanting, use subsurface driponly in turf and perennial areas that aregoing to be left alone.

Buried drip watering has many advan-tages over sprinkler irrigation:

• no water loss from evaporation

• no overspray even in small orirregular areas or on nearbywindows

• the system is not subject to damagefrom foot and vehicle traffic orvandalism

• no runoff on slopes, and no water onsidewalks or fences

• the number of valves can be re-duced—more area can be wateredwith less available flow

• emitter line spacing, and thusprecipitation rate, can be adjustedto account for berms, slopes andflat areas

• grass roots grow deeper to seek thewater, making the lawn moredrought resistant, and reducingthatch build-up

Layout

A subsurface irrigation system for turfis a simple grid of drippers formed byparallel emitter lines. Emitter linesconsist of polyethylene tubing withdrip emitters installed by the factory atspecific intervals. Subsurface emitterlines do best when buried 4-6" belowthe surface and installed with air ventsand automatic flushing ends. Maximumspacing, for use in heavy clay soils, is18" spacing of lines with emitters 18"apart on the lines. In lighter soils, the

lateral water spread is not as great andtighter spacing is needed. The closestspacing ever needed is 12" spacing oflines with emitters 12" apart on thelines.

The emitter lines are placed 4 to 6inches below the soil. Laterals areconnected by headers on both ends.The second header provides a methodfor flushing the lines by an automatic

flush valve, which should be located ina valve box at the low end of thesystem. (See diagram)

The valve flushes any sediment fromthe tubing each time the system startsup, and then closes down to allownormal system operation. An air ventshould be installed for each zone at thehigh point to minimize suction ofsediment into the line when the waterdrains. The air vent can be in a buriedvalve box with adequate drainage. Ifan anti-siphon valve is used, anadditional air vent is not needed.Emitter lines are placed under the soilin one of three ways. The first is handtrenching, the second is a mechanicaltrencher that cuts a narrow slot, and thethird is with a pipe pulling vibratoryplow. There is no best method, but

usually site conditions suggest the mosteconomical approach.

If berms, slopes, and flat areas of turfexist on the same valve, the bermsshould have laterals closer together, theflat areas should have normal spacingand the sloped areas should have agreater distance between laterals.Laterals next to hardscapes should belocated no further than 4" from the

edge to prevent dry strips.

Once drip emitters are buried, rootintrusion into emitter paths becomes aconcern. The most successful solu-tion is produced by Toro®, whomanufactures its DL2000Rootguard®emitter line with Treflan® (a herbi-cide) fused into the plastic of theemitter path. When buried, Treflan isslowly released over fifteen to thirtyyears to prevent root growth into theemitter.

Another solution comes fromNetafim®, who manufacturesTechLine®. Their answer to rootintrusion is pulse irrigation (shortermore frequent cycles), and eachemitter has a cavity that drains fullybetween the internal flow path and theemitter opening.

Flush Vent

Air Vent

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The Most Efficient Way to Water Your Lawn

Subsurface Drip Irrigation