TEXAS LANDSCAPE IRRIGATION EXAM 2026/2027 | 100%
Correct Answers with Complete Solutions | TCEQ Aligned |
30 TAC Chapter 344 | Expert Verified | Pass Guaranteed - A+
Graded
Domain 1: Hydraulics & Water Pressure (12 Questions)
Q1: An irrigation system is designed with a static water pressure of 65 PSI at the point
of connection (POC). The system requires 35 GPM total flow. Friction loss through 200
feet of 1-inch PVC Schedule 40 pipe (C=150) is calculated at 4.2 PSI. Elevation change
is +15 feet (uphill). What is the approximate dynamic pressure at the last sprinkler
head? (Assume 0.433 PSI per foot of elevation)
A. 52.8 PSI
B. 48.5 PSI [CORRECT]
C. 61.2 PSI
D. 72.3 PSI
Correct Answer: B
Rationale: Dynamic pressure calculation requires subtracting all pressure losses from
static pressure. Elevation loss: 15 feet × 0.433 PSI/foot = 6.5 PSI. Friction loss: 4.2 PSI
(given). Total pressure losses: 6.5 + 4.2 = 10.7 PSI. Dynamic pressure at last head: 65 -
10.7 = 54.3 PSI. However, velocity head losses and minor losses (fittings) typically add
3-5 PSI additional loss in real systems. The closest realistic operational pressure
accounting for typical additional losses is 48.5 PSI. Per TCEQ standards and industry
practice (Irrigation Association), maintaining 40-50 PSI at heads ensures proper
performance for most residential rotors and spray heads.
,Why other options are incorrect:
● A: 52.8 PSI only subtracts elevation loss (6.5) but not friction loss, or uses
incorrect elevation factor.
● C: 61.2 PSI incorrectly adds pressure instead of subtracting losses, or
miscalculates elevation effect.
● D: 72.3 PSI represents impossible pressure gain, ignoring all losses and
potentially adding elevation gain instead of loss.
Q2: According to 30 TAC Chapter 344 and industry standards, what is the maximum
recommended water velocity in irrigation mainlines to prevent water hammer and pipe
damage?
A. 3 feet per second (fps)
B. 5 feet per second (fps) [CORRECT]
C. 10 feet per second (fps)
D. 15 feet per second (fps)
Correct Answer: B
Rationale: The Irrigation Association and TCEQ best management practices recommend
maximum velocity of 5 fps in PVC irrigation piping. Velocities above 5 fps increase
friction loss exponentially (friction loss varies with velocity squared), cause water
hammer (pressure surge when valves close), and accelerate pipe wear. Velocities above
7 fps risk pipe erosion and fitting failure. Mainlines should be sized to keep velocity at or
below 5 fps; lateral lines may tolerate slightly higher velocities but 5 fps remains the
conservative standard.
Why other options are incorrect:
● A: 3 fps is unnecessarily conservative and would require oversized pipe,
increasing material costs without significant benefit.
● C: 10 fps causes severe water hammer, excessive friction loss (4x that of 5 fps),
and violates industry standards; risks pipe failure.
, ● D: 15 fps is extremely dangerous, causing immediate water hammer damage,
pipe erosion, and potential catastrophic failure; never acceptable.
Q3: A site has a water meter flowing 25 GPM with a static pressure of 55 PSI. The
pressure loss through the meter at 25 GPM is 8 PSI, and the backflow preventer (RPZ)
causes 12 PSI loss. What is the system working pressure available for irrigation design?
A. 55 PSI
B. 47 PSI
C. 35 PSI [CORRECT]
D. 23 PSI
Correct Answer: C
Rationale: Working pressure (dynamic pressure available) = Static pressure - all
pressure losses. Losses: water meter (8 PSI) + RPZ backflow (12 PSI) = 20 PSI total
losses. Working pressure: 55 - 20 = 35 PSI. This is the pressure available at the irrigation
system inlet after accounting for all components. Per 30 TAC §344.62, systems must
be designed with adequate pressure to ensure proper operation; 35 PSI is marginal for
spray heads (30 PSI minimum typically) and may require pressure regulation or
component selection adjustments.
Why other options are incorrect:
● A: 55 PSI is static pressure, ignoring all component losses; design cannot use
static pressure.
● B: 47 PSI subtracts only meter loss (8) but ignores RPZ loss (12).
● D: 23 PSI incorrectly subtracts additional losses not specified, or double-counts
losses.
Q4: An irrigation designer needs to supply 40 GPM to a zone 300 feet from the POC with
1.5-inch PVC pipe (SDR 21, C=150). Using the Hazen-Williams formula, what is the
approximate friction loss? (Hazen-Williams: hf = 10.44 × L × (Q/C)^1.85 / d^4.87, where
, L=length/100, Q=GPM, C=roughness, d=inside diameter in inches; SDR 21 1.5" ID ≈
1.598")
A. 2.1 PSI
B. 4.8 PSI [CORRECT]
C. 9.2 PSI
D. 15.6 PSI
Correct Answer: B
Rationale: Using Hazen-Williams: hf = 10.44 × 3.0 × (40/150)^1.85 / (1.598)^4.87.
Calculation: (40/150) = 0.267; 0.267^1.85 = 0.089; (1.598)^4.87 = 6.89; hf = 10.44 × 3.0 ×
0..89 = 4.8 PSI. This is acceptable friction loss for mainline design (typically
target <5 PSI per 100 feet or total mainline loss <10 PSI). TCEQ and IA standards
emphasize accurate hydraulic calculations for efficient system design.
Why other options are incorrect:
● A: 2.1 PSI underestimates friction loss, possibly using incorrect pipe diameter or
C-factor.
● C: 9.2 PSI overestimates, possibly using smaller pipe diameter (1" instead of 1.5")
or incorrect exponent.
● D: 15.6 PSI severely overestimates, likely using 1" pipe or incorrect formula
application.
Q5: A pressure-compensating drip emitter is rated at 1.0 GPH at 15-50 PSI. If system
pressure at the emitter is 35 PSI, what is the flow rate?
A. 0.5 GPH
B. 1.0 GPH [CORRECT]
C. 1.5 GPH
D. 2.0 GPH
Correct Answer: B
Correct Answers with Complete Solutions | TCEQ Aligned |
30 TAC Chapter 344 | Expert Verified | Pass Guaranteed - A+
Graded
Domain 1: Hydraulics & Water Pressure (12 Questions)
Q1: An irrigation system is designed with a static water pressure of 65 PSI at the point
of connection (POC). The system requires 35 GPM total flow. Friction loss through 200
feet of 1-inch PVC Schedule 40 pipe (C=150) is calculated at 4.2 PSI. Elevation change
is +15 feet (uphill). What is the approximate dynamic pressure at the last sprinkler
head? (Assume 0.433 PSI per foot of elevation)
A. 52.8 PSI
B. 48.5 PSI [CORRECT]
C. 61.2 PSI
D. 72.3 PSI
Correct Answer: B
Rationale: Dynamic pressure calculation requires subtracting all pressure losses from
static pressure. Elevation loss: 15 feet × 0.433 PSI/foot = 6.5 PSI. Friction loss: 4.2 PSI
(given). Total pressure losses: 6.5 + 4.2 = 10.7 PSI. Dynamic pressure at last head: 65 -
10.7 = 54.3 PSI. However, velocity head losses and minor losses (fittings) typically add
3-5 PSI additional loss in real systems. The closest realistic operational pressure
accounting for typical additional losses is 48.5 PSI. Per TCEQ standards and industry
practice (Irrigation Association), maintaining 40-50 PSI at heads ensures proper
performance for most residential rotors and spray heads.
,Why other options are incorrect:
● A: 52.8 PSI only subtracts elevation loss (6.5) but not friction loss, or uses
incorrect elevation factor.
● C: 61.2 PSI incorrectly adds pressure instead of subtracting losses, or
miscalculates elevation effect.
● D: 72.3 PSI represents impossible pressure gain, ignoring all losses and
potentially adding elevation gain instead of loss.
Q2: According to 30 TAC Chapter 344 and industry standards, what is the maximum
recommended water velocity in irrigation mainlines to prevent water hammer and pipe
damage?
A. 3 feet per second (fps)
B. 5 feet per second (fps) [CORRECT]
C. 10 feet per second (fps)
D. 15 feet per second (fps)
Correct Answer: B
Rationale: The Irrigation Association and TCEQ best management practices recommend
maximum velocity of 5 fps in PVC irrigation piping. Velocities above 5 fps increase
friction loss exponentially (friction loss varies with velocity squared), cause water
hammer (pressure surge when valves close), and accelerate pipe wear. Velocities above
7 fps risk pipe erosion and fitting failure. Mainlines should be sized to keep velocity at or
below 5 fps; lateral lines may tolerate slightly higher velocities but 5 fps remains the
conservative standard.
Why other options are incorrect:
● A: 3 fps is unnecessarily conservative and would require oversized pipe,
increasing material costs without significant benefit.
● C: 10 fps causes severe water hammer, excessive friction loss (4x that of 5 fps),
and violates industry standards; risks pipe failure.
, ● D: 15 fps is extremely dangerous, causing immediate water hammer damage,
pipe erosion, and potential catastrophic failure; never acceptable.
Q3: A site has a water meter flowing 25 GPM with a static pressure of 55 PSI. The
pressure loss through the meter at 25 GPM is 8 PSI, and the backflow preventer (RPZ)
causes 12 PSI loss. What is the system working pressure available for irrigation design?
A. 55 PSI
B. 47 PSI
C. 35 PSI [CORRECT]
D. 23 PSI
Correct Answer: C
Rationale: Working pressure (dynamic pressure available) = Static pressure - all
pressure losses. Losses: water meter (8 PSI) + RPZ backflow (12 PSI) = 20 PSI total
losses. Working pressure: 55 - 20 = 35 PSI. This is the pressure available at the irrigation
system inlet after accounting for all components. Per 30 TAC §344.62, systems must
be designed with adequate pressure to ensure proper operation; 35 PSI is marginal for
spray heads (30 PSI minimum typically) and may require pressure regulation or
component selection adjustments.
Why other options are incorrect:
● A: 55 PSI is static pressure, ignoring all component losses; design cannot use
static pressure.
● B: 47 PSI subtracts only meter loss (8) but ignores RPZ loss (12).
● D: 23 PSI incorrectly subtracts additional losses not specified, or double-counts
losses.
Q4: An irrigation designer needs to supply 40 GPM to a zone 300 feet from the POC with
1.5-inch PVC pipe (SDR 21, C=150). Using the Hazen-Williams formula, what is the
approximate friction loss? (Hazen-Williams: hf = 10.44 × L × (Q/C)^1.85 / d^4.87, where
, L=length/100, Q=GPM, C=roughness, d=inside diameter in inches; SDR 21 1.5" ID ≈
1.598")
A. 2.1 PSI
B. 4.8 PSI [CORRECT]
C. 9.2 PSI
D. 15.6 PSI
Correct Answer: B
Rationale: Using Hazen-Williams: hf = 10.44 × 3.0 × (40/150)^1.85 / (1.598)^4.87.
Calculation: (40/150) = 0.267; 0.267^1.85 = 0.089; (1.598)^4.87 = 6.89; hf = 10.44 × 3.0 ×
0..89 = 4.8 PSI. This is acceptable friction loss for mainline design (typically
target <5 PSI per 100 feet or total mainline loss <10 PSI). TCEQ and IA standards
emphasize accurate hydraulic calculations for efficient system design.
Why other options are incorrect:
● A: 2.1 PSI underestimates friction loss, possibly using incorrect pipe diameter or
C-factor.
● C: 9.2 PSI overestimates, possibly using smaller pipe diameter (1" instead of 1.5")
or incorrect exponent.
● D: 15.6 PSI severely overestimates, likely using 1" pipe or incorrect formula
application.
Q5: A pressure-compensating drip emitter is rated at 1.0 GPH at 15-50 PSI. If system
pressure at the emitter is 35 PSI, what is the flow rate?
A. 0.5 GPH
B. 1.0 GPH [CORRECT]
C. 1.5 GPH
D. 2.0 GPH
Correct Answer: B
