Mississippi Irrigation Systems Examination

On an irrigation plan, what does the abbreviation GPM represent?

• AGallons per minute of flow
• BGrains per minute of hardness
• CGauge pressure in millibars
• DGround pressure modulus

When is static water pressure measured on an irrigation supply?

• AWhile the largest zone is running at design flow
• BAfter the pump is shut off and the piping is drained
• COnly at the farthest sprinkler during operation
• DWith the system pressurized and no water flowing

How many feet of water head equal 1 psi?

• A0.433 ft
• B1.00 ft
• C2.31 ft
• D14.7 ft

A sprinkler zone climbs 20 ft from the point of connection to the highest head. About how much pressure is lost to elevation alone?

• A8.7 psi
• B4.3 psi
• C20 psi
• D46 psi

Using V = 0.4085 × Q ÷ d², what is the velocity in 1 in Schedule 40 PVC (inside diameter 1.049 in) carrying 13 GPM?

• A2.4 ft/s
• B3.6 ft/s
• C4.8 ft/s
• D7.2 ft/s

Why do irrigation designers commonly limit PVC mainline velocity to about 5 ft/s?

• ATo keep the pipe full so air cannot enter the system
• BBecause PVC cannot carry water faster than 5 ft/s under any pressure
• CTo satisfy a minimum-velocity scouring requirement
• DTo reduce friction loss, surge pressure, water hammer, and long-term wear

What Hazen–Williams C-factor is normally used for new smooth PVC irrigation pipe?

• A80
• B100
• C130
• D150

A Class 200 PVC main has a table friction loss of 3.2 psi per 100 ft at the design GPM. What is the friction loss in 250 ft of that main?

• A3.2 psi
• B6.4 psi
• C8.0 psi
• D11.2 psi

A zone demands 18 GPM. Using a 5 ft/s limit, 1 in Schedule 40 PVC (ID 1.049 in) is limited to about 13 GPM and 1-1/4 in Schedule 40 (ID 1.380 in) is limited to about 23 GPM. What is the smallest listed size that is acceptable?

• A3/4 in Schedule 40
• B1 in Schedule 40
• C1-1/4 in Schedule 40
• D2 in Schedule 40

Compared with Class 200 PVC of the same nominal size, Schedule 40 PVC has which property?

• AA thicker wall and a higher pressure rating
• BA thinner wall and a lower pressure rating
• CThe same wall thickness and the same inside diameter
• DA larger inside diameter and more flow capacity

What is the correct solvent-weld sequence for Schedule 40 PVC irrigation fittings?

• ACement only; primer is never used on pressure pipe
• BApply primer to soften the surfaces, then apply solvent cement and assemble with a quarte…
• CHeat the pipe until it is pliable, then push it into a dry fitting
• DThread the pipe with pipe dope and screw it into a solvent-weld socket

A 200 ft lateral would lose 4.0 psi per 100 ft if the full zone flow traveled the entire length. Ten equally spaced heads give a multiple-outlet factor of 0.40. What friction loss should be used for the lateral?

• A1.6 psi
• B3.2 psi
• C8.0 psi
• D16.0 psi

Why are pop-up sprinklers usually connected with swing joints or flexible swing pipe instead of a rigid riser off the lateral?

• ATo increase the nozzle precipitation rate
• BTo absorb traffic loads and allow the head to be set plumb at finished grade
• CTo eliminate the need for a zone valve
• DTo raise operating pressure at the nozzle

What is the primary purpose of a manual isolation (shutoff) valve on an irrigation main?

• ATo regulate precipitation rate at each head
• BTo replace the backflow preventer
• CTo start and stop the pump on a timed schedule
• DTo shut off water so a section can be repaired without draining the entire site

A typical electric remote-control irrigation valve is which type of device?

• AA 120 VAC motorized gate valve that fails open
• BA 24 VAC solenoid-pilot valve that is normally closed
• CA battery-only mechanical timer built into the valve box
• DA pressure-vacuum breaker that also zones the system

The last head needs 30 psi. Losses from the point of connection are 5 psi in the main, 4 psi in the valve, 3 psi in the lateral, and 8 psi of uphill elevation. What minimum dynamic pressure is required at the point of connection?

• A30 psi
• B38 psi
• C42 psi
• D50 psi

Where is a master valve installed, and what does it do?

• AAt each head, to match precipitation rates
• BOn the main after the point of connection, closed except when a station is running, to li…
• COn the controller common wire only, with no piping connection
• DAt the lowest head, to drain the lateral after each cycle

When an irrigation system is connected to a potable water supply, what protection is required at the connection?

• AAn approved backflow prevention assembly or device
• BNo protection is required if the heads are downstream of a zone valve
• CA hose-thread vacuum breaker on one hose bib only
• DA check valve inside each sprinkler, with no assembly at the source

What is the standard minimum installation height for a pressure vacuum breaker (PVB) on an irrigation system?

• AFlush with finished grade in a valve box
• B6 in above finished grade, regardless of head elevation
• C12 in above the highest downstream sprinkler or emitter
• D36 in below the meter so it stays below the heads

Which restriction applies to an atmospheric vacuum breaker (AVB) used for irrigation?

• AIt may be installed below grade if it is in a valve box
• BNo control valves may be installed downstream, and it must be at least 6 in above the hig…
• CIt is the only assembly approved for high-hazard chemical injection
• DIt must be 12 in above grade but may have any number of downstream zone valves

Which backflow assembly provides the highest protection and is used when irrigation presents a high hazard or possible back-pressure?

• AHose-connection vacuum breaker
• BAtmospheric vacuum breaker
• CDual check (non-testable)
• DReduced-pressure principle assembly (RP or RPZ)

What is a quick-coupling valve used for on a commercial irrigation main?

• ATo automatically drain the main after every cycle
• BTo accept a key and hose swivel so workers can take water without cutting the pipe
• CTo reduce pressure for drip laterals
• DTo serve as the required backflow preventer

A zone is designed for 40 psi at the heads. Using the common 20 percent pressure-variation guideline, what is the acceptable pressure range in that zone?

• A20 to 60 psi
• B30 to 50 psi
• C32 to 48 psi
• D38 to 42 psi

Which statement correctly compares a ball valve and a gate valve used as irrigation isolation valves?

• AA ball valve opens or closes with a quarter turn; a gate valve takes multiple turns and i…
• BA gate valve is always the better choice for frequent on-off cycling of a zone
• CA ball valve cannot be used on PVC mains
• DBoth valves are designed to be left half-open as pressure regulators

What is the main reason to install a spring check valve or an in-head check on a downhill lateral?

• ATo increase the precipitation rate at the top of the slope
• BTo prevent low-head drainage that empties the line through the lowest heads after shutoff
• CTo replace the backflow preventer at the meter
• DTo keep static pressure from exceeding the pipe rating

Why are remote-control valves installed in valve boxes rather than buried directly in soil?

• ABoxes increase the valve pressure rating
• BBoxes provide access for wiring, flow-control adjustment, and repair without excavation
• CCodes prohibit any valve that is not in a box from controlling water
• DBoxes replace the need for waterproof wire connectors

A drip zone is fed from a 50 psi main. The emitters are rated at 20 to 30 psi. What device should be installed at the drip manifold?

• AA pressure-increasing booster only
• BA pressure-regulating valve (and usually a filter) to bring the lateral down into the emi…
• CA PVB installed below the emitters
• DA 2 in mainline tee with no regulation

Where are concrete thrust blocks (or restrained joints) required on gasketed irrigation mains?

• AOnly on solvent-weld Schedule 40 laterals
• BAt tees, elbows, dead ends, and other fittings where unbalanced thrust would separate a g…
• CUnder every sprinkler swing joint
• DOnly on copper tube

Using V = 0.4085 × Q ÷ d², what is the velocity in 2 in Schedule 40 PVC (ID 2.067 in) carrying 45 GPM?

• A2.1 ft/s
• B3.3 ft/s
• C4.3 ft/s
• D6.8 ft/s

What is the difference between an irrigation mainline and a lateral?

• AThe mainline is pressurized whenever the source is on; a lateral is pressurized only when…
• BLaterals always run at higher pressure than mains
• CMains may be polyethylene only; laterals must be copper
• DThere is no hydraulic difference; the names are only for plan symbols

A 300 ft main loses 2.0 psi per 100 ft at design flow and drops 12 ft in elevation toward the last valve. What is the net pressure change along that main?

• A11.2 psi loss
• B6.0 psi loss
• C0.8 psi loss
• D5.2 psi gain

Where should a combination air/vacuum relief valve be placed on an irrigation main?

• AAt the lowest point of each lateral only
• BAt high points where air collects and where a draining line could collapse
• COn the suction side of every spray nozzle
• DInside the controller cabinet

Four zones demand 12, 18, 24, and 9 GPM. Only one zone runs at a time. For what flow should the mainline and water meter be sized?

• A9 GPM, the smallest zone
• B15.8 GPM, the average of the four zones
• C24 GPM, the largest zone
• D63 GPM, the sum of all zones

Which combination most effectively reduces water hammer in an irrigation system?

• AHigher velocity, instantaneous electric-valve closure, and no air relief
• BVelocity near or below 5 ft/s, slow-closing valves, and proper air management
• COversized nozzles and no isolation valves
• DRunning every zone at the same time to keep pipes full

In the Hazen–Williams equation, friction loss varies with flow to about the 1.85 power. If flow in a PVC main doubles and everything else stays the same, friction loss becomes about how many times as large?

• A1.85 times
• B2.0 times
• C3.6 times
• D8.0 times

What is the first information a designer should obtain before laying out an irrigation system?

• AAvailable flow (GPM) and working pressure at the point of connection
• BThe controller brand and station count
• CThe color of the proposed nozzles
• DThe owner's preferred watering day only

A bucket test at the hose bib nearest the point of connection fills a 5-gallon container in 20 seconds. What is the available flow?

• A5 GPM
• B10 GPM
• C15 GPM
• D20 GPM

Which items belong on the plot plan used to design an irrigation system?

• AOnly the water-meter brand
• BOnly plant botanical names
• COnly the controller programming worksheet
• DProperty lines, buildings, hardscape, existing trees and beds, and the water-source locat…

What is hydrozoning?

• ARunning every head on the site from one valve to save wire
• BGrouping plants and areas with similar water need, sun exposure, soil, and slope onto the…
• CSizing pipe by average instead of peak flow
• DPlacing the backflow preventer below grade

In what order should sprinkler heads be placed on a rectangular lawn?

• AInterior heads first, then guess at the edges
• BCorners first, then sides, then interior heads to complete head-to-head coverage
• COne head in the center of the lawn only
• DAlong the water main only, regardless of the lawn shape

A driveway 12 ft wide separates two turf panels. What layout practice is correct?

• AAim full-circle rotors across the pavement so one zone waters both panels
• BUse part-circle heads on each side so spray stays on the turf and off the pavement
• CPlace one row of heads down the center of the driveway
• DIncrease precipitation rate so some water still reaches the far panel

A proposed zone has six full-circle rotors at 3.5 GPM and four half-circle rotors at 1.75 GPM. Available supply is 22 GPM. What should the designer do?

• AInstall all ten heads on one valve because the average is under 22 GPM
• BSplit the heads into two (or more) stations so no station exceeds 22 GPM
• CKeep one zone and reduce each nozzle to 0 GPM
• DIgnore supply and rely on the controller to limit flow

For the same sprinkler radius, how does triangular spacing compare with square spacing?

• ATriangular spacing usually gives more uniform coverage and can use fewer heads, with row…
• BTriangular spacing eliminates the need for head-to-head overlap
• CTriangular spacing always requires more heads and a higher precipitation rate
• DTriangular spacing reduces the operating pressure each head needs

An irrigation plan is drawn at a scale of 1 in = 20 ft. A lawn measures 3.0 in by 4.5 in on the sheet. What are the true dimensions?

• A3 ft by 4.5 ft
• B20 ft by 30 ft
• C60 ft by 90 ft
• D80 ft by 120 ft

What should as-built irrigation drawings show that the original design plan may not?

• AOnly the original schematic with no field changes
• BThe actual installed locations of valves, mains, laterals, heads, wire routes, and the po…
• COnly the controller password
• DOnly the plant warranty dates

Which topics belong in a written irrigation specification?

• APipe material and class, burial depth, pressure-test method, backflow type, and acceptabl…
• BOnly the owner's favorite plant color
• COnly a verbal agreement on head count
• DOnly the PSI exam fee

On an irrigation drawing, what is the point of connection (POC)?

• AThe farthest sprinkler on the last zone
• BThe location where the irrigation piping taps the water source, including meter, backflow…
• CThe controller transformer only
• DAny swing joint at a head