Terminology

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ABSORPTION RATE - The rate at which a soil will accept water (the speed at which the water can infiltrate the soil). This rate decreases as the soil "capacity" is reached (affected by soil type, slope, run-off, etc.) Different types of soil absorb water at different rates, i.e. sandy soil will accept water at a faster rate than clay soil. (Also called percolation rate)

ACTUAL HEAD PRESSURE - Operating pressure at the base of a sprinkler head. Calculated by subtracting all pressure losses between the head and the pressure source, from the static pressure.

AIR GAP - According to the AWWA M14 Manual - "Recommended Practice for Backflow Prevention and Cross-Connection Control", an approved air gap is the unobstructed vertical distance through free atmosphere between the lowest point of a water supply outlet and the flood level rim of the fixture or assembly into which the outlet discharges. These vertical, physical separations must be at least twice the diameter of the water supply outlet, but never less than 1 in. (25 mm). A common air gap would be that of a typical household sink in which there is a gap between the water in the sink and the faucet above it.

ANTI-SIPHON DEVICE - Any device that introduces air into the system to prevent "back siphonage". See definitions for atmospheric vacuum breaker or pressure-type vacuum breaker below.

APPLICATION RATE - Rate at which water is applied by the irrigation system. It is usually measured in inches per hour, gallons per hour. Commonly called precipitation rate.

ARC - The surface area of the landscape to which a sprinkler head will provide water. Usually described in degrees or part of a full circle (360 degrees). The degrees of coverage of a sprinkler from one side of pattern to the other. For example, a 90 degree arc would be a quarter circle sprinkler, a 180 degree arc would be a half circle sprinkler, a 360 degree arc would be a full circle sprinkler, etc.

ARCHITECT SCALE - Scale expressing foot measurements in parts of an inch. Example: 1/8" = 1', 3/16" = 1', 1/4" = 1', etc.

AS-BUILT-PLAN - A corrected or redrawn plan (to scale) showing the actual location of all major components of the system and other information the property owner might require. See definition for "record drawing".

ATMOSPHERIC VACUUM BREAKER (AVB) - A backflow prevention device which introduces air into piping system to prevent back siphonage. Cannot be under constant pressure (constant pressure is defined as "more than 12 hours") The AVB must be installed at least 6" higher than all down stream piping and the highest downstream outlet. No backpressure may exist. No shut off valves may exist downstream of the AVB.

AUTOMATIC CONTROL VALVE - An electric or hydraulic remote control valve in a sprinkler system that is activated by an automatic controller. Also called a section valve, zone valve, or remote control valve.

AUTOMATIC SYSTEM - An irrigation system that will automatically cycle (water) according to a preset program.

AWWA - American Water Works Association.

BACK PRESSURE - Any condition that could create pressure in the discharge (outlet or downstream) side of the piping system that is greater than that in the supply (inlet or upstream) side of the system. Examples: pressure caused by gravity due to elevation differences; a pump installed in the system; or steam and/or air pressure.

BACK SIPHONAGE - A form of backflow due to negative or sub-atmospheric pressure within water system.

BACKFLOW - An undesired reversal of the flow of water in a piping system.

BACKFLOW PREVENTION - Any approved method that prevents an undesirable reversal of flow of water. Examples include the Air Gap, Atmospheric Vacuum Breaker (AVB), Pressure Vacuum Breaker (PVB), Double Check Valve Assembly DCA), and the Reduced Pressure Principle Device (RP).

BELL/SOCKET/SLIP - This is the term generally used to describe the male and female sections of PVC pipe. The male side of the pipe slides into the bell/socket end of the pipe. This type of pipe is solvent welded.

BERM - A raised section of earth that is built in place with earthen fill for the purposes of landscape or drainage control.

BLOCK (of heads) - A section of sprinklers controlled by one valve.

BLOCK SYSTEM - An irrigation system in which several groups of sprinklers are controlled by one valve for each group.

BODY (OF HEAD) - The exterior case or shell of a sprinkler.

BOOSTER PUMP - A pump that is installed in the water supply line and is designed to raise the pressure in the irrigation system.

BUSHING - The pipe fitting used to change an irrigation component to a larger or smaller size.

BY-PASS-VALVE - A pressure relief valve in a pumping station that opens when pumping pressure rises, dumping excess water back into the reservoir, eliminating repetitive on-off cycles of the pumps.

C-FACTOR - Rating of the smoothness of the inside of pipe. The higher the C-Factor, the smoother the inside diameter of the pipe. PVC has a C-Factor of 150, whereas copper is 140. Generally the C-Factor decreases over time indicating the pipe gets rougher, resulting in increased friction loss.

CHECK VALVE - A valve that permits water to flow in one direction only.

CLASS OF PIPE - A method by which PVC pipe is grouped according to the working pressure. Pressure rated with a wall thickness in direct ratio to the diameter. All sizes in that class have the same working pressure. (Class 160, Class 200, Class 315). See definition for S.D.R.

CONTOUR LINE - A line of equal elevation drawn on a plan. For example, a contour line labeled "510" means that everywhere along that line is 510 feet above mean sea level.

CONTROL WIRES - The wires that transmit the signals to open and close from the automatic controller to the automatic electric valves.

CONTROLLER - An automatic timing device, electro mechanical, digital, or a combination of both, which signals the automatic valves to open or close according to a prescribed program.

COPPER - A type of pipe that is made out of a copper alloy. It is no longer used on a regular basis in irrigation, but is still used on most plumbing application. There is a high probability that copper pipe will be encountered when making a cross connection to the potable water supply. Type "K" copper is predominately as the city service (from main line to water meter).

COUPLER KEY - A bronze tube with a handle which insets into a quick coupling valve for supplemental water. May be fit with a hose swivel or faucet. See definition for "Quick Coupler Valve".

CREEP - This phenomenon happens when pipe is installed and is subject to water hammer and dry line shock. The pipe actually stretches or "creeps" as it is subjected to the water hammer and dry line shock. Creep can lead to FATIGUE, which will ultimately lead to pipe failure.

CROSS-CONNECTION - Any actual or potential connection between a potable water supply and any source of contamination or pollution.

CYCLE - Refers to one complete operation of a controller through all programmed stations.

DESIGN - The graphic or dimensional location of sprinkler heads, piping, valves, backflow prevention device, etc, used to show the assembly of component parts of an irrigation system.

DESIGN PRESSURE - The sum total of the desired head pressure added to the total of all pressure losses. A stated pressure indicating the minimum pressure required if the system is to operate properly.

DESIRED HEAD PRESSURE - The manufacturer's minimum recommended operating pressure at the base of a specific head.

DIAPHRAGM - That portion (flexible membrane) of an automatic valve that regulates the passage of water through the valve.

DIELECTRIC FITTING - This specialty fitting is used to connect two dissimilar metals together. If a dielectric fitting is not used, then electrolysis will set in, and the weaker of the two dissimilar pipes will fail. PVC is a natural dielectric fitting.

DIRECT BURIAL WIRE - Any wire approved by the National Electric Code for direct underground burial without conduit. UL approved requires a minimum insulator thickness of 4/64". UF 14 is the smallest UL approved wire at this time.

DISTRIBUTION - The manner in which a sprinkler applies water to the irrigated area.

DISTRIBUTION CURVE (OF A SPRINKLER HEAD) - A curve showing the rate of water application by a sprinkler at various points along the radius in inches per hour.

DISTRIBUTION PATTERN - The pattern of water application by a sprinkler over the area covered by the sprinkler.

DISTRIBUTION UNIFORMITY (DU) - The measure of the uniformity of irrigation water over an area. The measure of how uniform the water is made available to the plants over an area. DU is expressed as a percentage and generally represents the major component of irrigation efficiency. A DU of 1.0 (100% uniformity) represents all of the area will receive the same amount of water.

DOUBLE CHECK VALVE ASSEMBLY - Backflow prevention device using two shut-off valves and two check valves assembled and pre-tested at the factory, designed to physically prevent the backflow of water. Also called a double gate/double check assembly.

DRAIN VALVE - An automatic or manual valve used to drain water from a line.

DRIP IRRIGATION - The slow application (low volume) of water, usually under low pressure, to the specific root zone area of the plant material.

DRY LINE SHOCK - The shock that occurs when a section valve is opened and the water travels unrestricted in empty lateral piping. Air in piping is quickly voided through heads allowing velocities that would not normally occur. Damages heads and piping.

DUAL PROGRAMMING - The feature on some automatic controllers that allows two different watering schedules or programs.

DYNAMIC PRESSURE - The pressure of water as it is moving through the system. Also called working pressure.

ELECTROLYSIS - A metallurgical phenomena that occurs when two dissimilar metals are connected together. This phenomena causes an electron flow to move between the two dissimilar metals causing the weaker metal to fail.

ELECTRIC VALVES - Automatic valves usually controlled by a 24-30 volt current carried in direct burial ground wire between the controller and valves.

ELEVATION GAIN - Pressure gained as water is used downhill from its source. It is figured at the pressure gain rate of .433 pounds per square inch for each foot of elevation lost.

ELEVATION LOSS - Pressure lost as water is used uphill from its source. It is lost at the rate of .433 lbs. for each foot of elevation gained.

EMITTERS - A mechanical device to limit water flow to a drip or slow trickle. Discharge rate in gallons per hour rather than gallons per minute.

E.T.-BASED SCHEDULING - A type of irrigation scheduling that is determined via the actual landscape needs vs. a calendar and a clock. The E.T. method allows the plant material to have the water replaced on an "as needed" basis.

EVAPORATION - The natural process of changing water into vapor.

EVAPOTRANSPIRATION - The combination of evaporation and transpiration from plant material.

FATIGUE - The process of a pipe wearing down due to constant pipe creep, water hammer, electrolysis, dry line shock, etc. to the point where the pipe actually fails.

FIP - Abbreviation for "Female Iron Pipe".

FLOW - The movement of water in a piping system.

FLOW CONTROL VALVE - A valve that can be mechanically adjusted to restrict flow and thus discharge pressure.

FLOW RESTRICTIONS - Physical restrictions in a piping system that affect the flow of water causing a pressure loss.

FLUSH FLOW - The higher initial momentary flow through a drip or trickle system required to flush emitters before pressure compensation occurs.

FOOT-HEAD ("FEET OF HEAD") - A measure of pressure equivalent to .433 lbs. per square inch and equal to weight of one foot of water.

FRICTION LOSS - A calculation of pressure consumed via water moving through a pipe encountering resistance via velocity, length, volume, size, and pressure.

G.P.M. - Abbreviation for "gallons per minute".

GATE VALVE - Manual valve with straight-through flow using wedge type metal-to-metal or restricting partial seating surfaces. Not suitable for throttling section flow. Not suitable for section valves in an irrigation system.

GAUGE (WIRE) - Standards used for wire sizing. The larger the gauge number, the smaller the wire.

GLOBE VALVE - A valve that uses a rubber or composition seat against the valve body used to restrict or stop the flow of water. Can be either straight through or angle configuration.

HAZARD (Degree of) - Irrigation system with no back pressure on backflow device is rated as "low hazard". With fertilizer injector, system is rated as a "high hazard" and Reduced Pressure Principle backflow device must be used.

HEAD SPACING - The spacing between sprinkler heads.

HEAD TO HEAD SPACING - Spacing of heads is approximately equal to the published radius (plus or minus 5%) of the head. Spacing most frequently recommended by manufacturers of rotary heads for triangular spacing.

HYDRAULICALLY CONTROLLED - A system that uses water pressure through tubing to operate remote control valves.

I.D. - Inside diameter; the measurement generally used in reference to the inside measurement of pipe. The difference between O.D. (outside diameter) and the I.D. is the wall thickness of a given pipe.

INSERT FITTINGS - A fitting that fits into pipe. Usually used on polyethylene pipe and tubing.

IPS - "Iron Pipe Size"; a rating that has been established to define a given type of pipe and how it is measured. It refers back to the iron pipe that was used prior to the development and use of PVC pipe. PVC pipe utilizes IPS measurements.

LATERAL PIPING - Piping after the remote control valve not subject to constant main line pressure.

LOOP MAIN LINE - A looped main line is a main line designed to provide water to any valve from two or more directions.

MAIN LINE - That portion of the piping under constant pressure located between the water source or remote control valves or quick coupler valves.

MANUAL SYSTEM - A system where control valves are operated manually.

MASTER VALVE - An automatic or manual valve installed at the supply point that controls water flow into the system mainline piping.

MIP - Abbreviation for "Male Iron Pipe".

NON-POTABLE WATER - Water not suitable for human consumption.

NORMALLY CLOSED VALVE - An automatic valve through which no water will flow unless external influences are applied to cause the valve to open. All electric valves are "normally closed type".

NORMALLY OPEN VALVES - An automatic valve through which water will flow unless external influences are applied to close the valve. All hydraulic valves are "normally open".

NOZZLE TREE - Refers to the interchangeable nozzle assortment, with different G.P.M. provided with many plastic gear driven heads.

O.D. - The outside diameter; the measurement generally used for the outside measurement of pipe. All pipe is measured by its outside diameter.

P.O.C. - Abbreviation for "Point-of-Connection.

PRIMER - A type of chemical that is used to clean and prepare PVC pipe and fittings to be solvent welded.

P.S.I. - Abbreviation for "Pounds-per-Square-Inch".

P.V.C. PIPE - Abbreviation for unplasticized PolyVinyl Chloride pipe.

POLYETHYLENE PIPE - Abbreviation for black, flexible plastic pipe that uses insert fittings for flexible connection between lateral pipe and head. Poly Nipple is semi-flexible threaded nipple used between lateral pipe and fittings.

POTABLE WATER - Treated water that is meant for human consumption. It can be used for irrigation systems as long as protection is provided to prevent contamination of the domestic supply.

PRESSURE COMPENSATING - A method of maintaining a constant discharge pressure regardless of inlet pressure.

PRESSURE LOSS - The loss of pressure under flow conditions caused by friction or elevation.

PRESSURE RATING - A method of controlling the wall thickness of PVC pipe so all sizes of pipe in a "class" have the same pressure rating. See definition for S.D.R.

PRESSURE RELIEF VALVE - A valve that will open when the inlet pressure exceeds a preset pressure.

PRESSURE TO DESIGN TO - A general rule of thumb used in system design equal to the low static pressure less 10% allowance for fluctuation.

PRESSURE VACUUM BREAKER (P.V.B.) A backflow prevention device that introduces air into the system to prevent "back siphonage". Incorporates the use of a spring-loaded seat for positive opening to atmosphere. Will operate under constant pressure. Commonly used for high hazard application with no back pressure. The assembly must be installed at least 12 inches above all downstream piping and the highest downstream outlet.

PUMP CIRCUIT - The optional switch on some automatic controllers that energizes a pump starter when controller operation begins.

QUICK COUPLING VALVE - A constantly pressurized valve set vertically in the ground to provide supplemental water when a coupler key is inserted and turned one and a quarter revolutions. On the irrigation main line, the cover must be purple to indicate non-potable water.

R.P.P.,RPZ, OR R.P. - Reduced pressure principle backflow prevention device commonly used for high hazard applications. Uses a combination of check valves and an air chamber or zone that is open to atmosphere.

RECORD DRAWING - A drawing of installed irrigation system showing the location of major components either scaled on the drawing or shown by dimension not to scale.

S.D.R. - Abbreviation for "standard dimension ratio". Relates to wall thickness of Class PVC pipe. S.D.R. 26 equals Class 160; S.D.R. 21 equals Class 200; S.D.R. 13.5 equals Class 315. No wall thickness can be less than .060 inches. It is a thinner wall thickness than schedule pipe.

SADDLE - A type of fitting which attaches around the pipe. A hole is drilled through the pipe to furnish water to the outlet of the saddle that is usually threaded F.I.P.

SCHEDULE PIPE - PVC pipe that has the same physical dimensions as iron pipe. Smaller sizes have higher working pressure than larger sizes. Example: Schedule 40 and Schedule 80. This schedule rating applies to metal and thermoplastic pipe.

SECTION OF HEADS - A group of sprinklers controlled by one valve. Also, known as a zone.

SLEEVES - Piping or conduit under hardscape provided for irrigation system piping or wiring. Generally sized 2 sizes larger than irrigation piping required.

SLIP FITTING - A smooth wall male or female fitting solvent welded to PVC pipe rather than screwed on a thread.

SLOPE - A measure of the rate of change of elevation over a prescribed distance. Slope may be expressed as a ration, a grade, or as a percent.

SOILS/TYPES OF - There are three basic types of soil: sand, loam, and clay. Most soils are a combination of two or more of these types.

SOLVENT - A material that causes a partial dissolving of PVC pipe and fittings so that a chemical fusion occurs between the pipe and fitting.

SOLVENT WELDING - The act of chemically fusing pipe and fittings together using solvent and cement. Incorrectly called or referred to as gluing.

SPACING - The triangular or square distance between sprinkler heads.

STATIC PRESSURE - The pressure of water when it is not moving.

SURGE - An energy wave in pipe lines caused by sudden opening or closing of valves. See definition for "water hammer".

SWING JOINT - A flexible joint or pipe connecting a sprinkler head to a pipe. The swing joint is intended to provide protection from damage. In larger applications (institutional or golf course) it could be a series of three 90-degree street ells with schedule 40 pipe nipples in between the ells.

THREADED FITTING - A fitting that is threaded vs. solvent welded. Most iron pipe threads that are PVC have a tapered fitting of one thousandth of an inch per thread. This allows the fitting to get progressively tighter without shouldering the fitting. This is important to note, as it is possible to break the fittings if over-tightened.

TOPOGRAPHICAL (TOPO) - A series of lines on a plot plan that indicate the height or elevation changes or contour. These are generally measured in distances above sea level.

TRANSPIRATION - The process of plant material giving off water vapor from the leaves.

TUBING (SPAGHETTI) - Small tubing used in drip or trickle systems to carry water from emitter(s) to a specific plant.

UNIFORMITY OF APPLICATION - A general term designating how uniform the application of water is between heads.

VALVE CENTERED FEEDING - A design technique in which the control valves are placed in the approximate center for increased performance and allows the use of smaller pipe.

VALVE IN HEAD - Indicates that the automatic control valve is part of the sprinkler.

VELOCITY OF WATER - The speed at which water travels through piping.

WATER HAMMER - A shock wave in the piping system usually created by excessive flow velocity and/or a fast closing valve.

WATER SCHEDULE - The procedure of establishing and implementing the time, frequency, and amount of irrigation water application.

WATER WINDOW - An allotted time available for watering through an irrigation system, usually within a 24-hour period. May have a water window once a week, or every five days.

WALL THICKNESS - The measurement of the wall of pipe. This is determined by the distance between the inside and outside diameter of pipe.

WORKING PRESSURE - The pressure rating of a given pipe that defines its maximum working range. For example, a class 200 pipe has a working pressure up to 200 PSI.

Landscape Irrigation Licensing

Please see: www.tceq.state.tx.us/compliance/compliance_support/licensing/landscape_lic.html The website above will give an "easy-to-understand-and-study" interpretation of the Texas law governing the irrigation industry.