Sec 4 Sprinkler Systems

Sprinkler Systems Valve in Head Usually used in large area like golf courses Each head is controlled individually by a valve at the base of the head Advantages of a VIH System Individual head control Maximum flexibility Minimal pipe sizing Allows looping of a system Easier to expand as the charged pipes are closer to new areas. Disadvantages of a VIH System Cost – wiring/ hardware/ sprinklers Always charge main and lateral lines Less isolation than a block system More complicated when it comes to trouble shooting. Block System Usually used in residential light commercial systems A series of sprinkler heads are run all at one time controlled by a valve at the beginning of each zone. Advantages Less expensive to install Less wires and hardware/sprinklers Does not weep past the block valve 24-hours/day More isolation than VIH Less to go wrong – troubleshooting Disadvantages Less control of the sprinkler zones Larger main lateral lines Variable pipe sizes – inventory 1 bad valve shuts down an entire block SPRINKLER TERMS TO KNOW Radius – the distance in which the sprinkler distributes water eg: 15’, 10 m etc. Arc – the pattern of water distributed by the sprinkler eg: 180o ,full circle etc. Angle of Trajectory – the angle horizontal to the ground that the nozzle is set to distribute water. Rotary heads have an angle of trajectory of approximately 22o – 25o Low angle nozzles are used for slopes and windy conditions. Some nozzles have 2 orifices with 2 different trajectory angles – This creates a rain curtain effect. ( better coverage) Flow – How much water flows through the sprinkler (gpm) Precipitation rate – how much water the sprinkler will distribute in “/hr precipitation rate takes into consideration GPM and area covered by the sprinkler. Precipitation rates should not exceed infiltration rates. Pressure – the ideal pressures the sprinkler is designed to run at. Distribution Patterns A sprinkler distributes water in a triangle pattern from the head out. A typical sprinkler distribution pattern with almost no wind has regular circular areas of distribution. Wind will create uneven coverage by distorting the distribution pattern. Running the sprinkler at the wrong pressure will also distort the distribution pattern. Too little pressure will result in very large water droplets that create a stream out of the nozzle. This will result in green directly around the nozzle and a green ring (GREEN DONUT) forming where the stream hits. Conversely too much pressure results in very small water droplets that just fall to the ground next to the sprinkler head. This will over water the area around the sprinkler and leave the outer areas dry, resulting in irregular brown circles (BROWN DONUTS) The best way to test the actual operating pressure of a sprinkler is to use a pitot tube for rotors and a pressure gauge for spray heads. This will give you the most accurate assessment of the system's operating pressure. TYPES OF SPRINKLERS Spray Heads http://www.irrigationtutorials.com/faq/heads-do-not-popup.htm Commonly used in the residential landscape market Limited to smaller areas Water in fixed spray pattern except for rotator nozzles. Low pressure 15-40 psi High precipitation rates .5 – 3.5”/hr Radius of 2’-18’ Nozzles vary from fixed sprays, adjustable, strip sprays, square sprays, rotators, Comes in different size pop ups 4” for turf, 12” for shrubs, flowers Also comes in pressure regulating (PRS) and check valve Rotary Heads Two basic types used today – gear drive and impact drive Most common sprinkler type in commercial landscapes and parks Water moves in a rotating pattern Medium pressure 30-100 psi Low precipitation rates; from 0.15”/hr to 0.55 “/hr Radius varies from 15’ to 200’ Patterns are fully adjustable – usually comes with a nozzle tree Impact Sprinklers A spring loaded arm taps the water stream sideways, gradually turning the sprinkler Usually made of metal but less expensive sprinklers can be made of plastic. Available in pop-ups Less popular because of the noise of the impact. https://www.holmanindustries.com.au/products/impact-sprinkler-head-metal/ Gear Drive Sprinklers A water driven rotor gradually turns the sprinkler through a series of reduction gears Gear Drive RotorCapRiser with nozzle SpringGearsBody inlet Gear Drive Rotor Cap Riser with nozzle Spring Gears Body inlet www.sprinklerwarehouse.com/adjust-rotor-head-rainbird-s/8292.htm Calculating Precipitation Rates The precipitation rate is the average rate at which the sprinklers apply water to a given area (expressed in inches/hour) Factors that affect the gross PR are sprinkler flow (in GPM) and the area with the spacing. A full circle sprinkler is calculated with the following formula PR = 96.3 x gpm S x L PR = precipitation rate 96.3 = a constant that converts cubic inches of water per gallon to inches/square foot per hour S = spacing in feet between sprinklers L = row spacing in feet Example: 4 full circle sprinklers are spaced at 70’ in a square pattern. They each use 31.3gpm PR = 96.3 x 31.3 = .62”/hr 70 x 70 Triangular spacing PR = 96.3 x gpm S x L x .866 Irregular shape PR = 96.3 x gpm of all sprinklers combined Area (A) Part circles square spacing PR = 96.3 x GPM x 360 S x L arc