A hydrant outlet 2.5 in. in diameter with a coefficient of 0.97 shows a pitot pressure of 35 psi. Static pressure is 71 psi and the residual pressure during the test is 25 psi. Compute the measured discharge and the flow available at a 20 psi residual.

Start with the thinking

• Hydrant flow testing uses Q = 29.83 C d²√p with d in inches, p in psi and Q in gpm.
• The 0.54 exponent projects the test to the standard 20 psi residual used for fire-flow ratings.

Step-by-step solution

1. Formula

   $$Q = 29.83\,C\,d^2\sqrt{p}$$

2. Substituting

   $$Q = 29.83(0.97)(2.5)^{2}\sqrt35 = 1,070 gpm$$

3. Formula

   $$Q_{20} = Q_{test}\left(\dfrac{p_s-20}{p_s-p_r}\right)^{0.54}$$

4. Pressure drops

   $$static - 20 = 51 psi; static - residual = 46 psi$$

5. Substituting

   $$Q_{20} = 1,070(51/46)^{0.54} = 1,131 gpm$$

Why the other options are there

• 428.0 gpm (diameter not squared)
• 1,186 gpm (0.54 exponent dropped)

Reference: FE Reference Handbook — Hydraulics → Fire Hydrant Discharging to Atmosphere

A hydrant outlet 2.5 in. in diameter with a coefficient of 0.90 shows a pitot pressure of 42 psi. Static pressure is 67 psi and the residual pressure during the test is 33 psi. Compute the measured discharge and the flow available at a 20 psi residual.

Start with the thinking

• Hydrant flow testing uses Q = 29.83 C d²√p with d in inches, p in psi and Q in gpm.
• The 0.54 exponent projects the test to the standard 20 psi residual used for fire-flow ratings.

Step-by-step solution

1. Formula

   $$Q = 29.83\,C\,d^2\sqrt{p}$$

2. Substituting

   $$Q = 29.83(0.90)(2.5)^{2}\sqrt42 = 1,087 gpm$$

3. Formula

   $$Q_{20} = Q_{test}\left(\dfrac{p_s-20}{p_s-p_r}\right)^{0.54}$$

4. Pressure drops

   $$static - 20 = 47 psi; static - residual = 34 psi$$

5. Substituting

   $$Q_{20} = 1,087(47/34)^{0.54} = 1,295 gpm$$

Why the other options are there

• 435.0 gpm (diameter not squared)
• 1,503 gpm (0.54 exponent dropped)

Reference: FE Reference Handbook — Hydraulics → Fire Hydrant Discharging to Atmosphere

A hydrant outlet 4.0 in. in diameter with a coefficient of 0.97 shows a pitot pressure of 39 psi. Static pressure is 55 psi and the residual pressure during the test is 27 psi. Compute the measured discharge and the flow available at a 20 psi residual.

Start with the thinking

• Hydrant flow testing uses Q = 29.83 C d²√p with d in inches, p in psi and Q in gpm.
• The 0.54 exponent projects the test to the standard 20 psi residual used for fire-flow ratings.

Step-by-step solution

1. Formula

   $$Q = 29.83\,C\,d^2\sqrt{p}$$

2. Substituting

   $$Q = 29.83(0.97)(4.0)^{2}\sqrt39 = 2,891 gpm$$

3. Formula

   $$Q_{20} = Q_{test}\left(\dfrac{p_s-20}{p_s-p_r}\right)^{0.54}$$

4. Pressure drops

   $$static - 20 = 35 psi; static - residual = 28 psi$$

5. Substituting

   $$Q_{20} = 2,891(35/28)^{0.54} = 3,261 gpm$$

Why the other options are there

• 722.8 gpm (diameter not squared)
• 3,614 gpm (0.54 exponent dropped)

Reference: FE Reference Handbook — Hydraulics → Fire Hydrant Discharging to Atmosphere

A hydrant outlet 4.5 in. in diameter with a coefficient of 0.97 shows a pitot pressure of 32 psi. Static pressure is 43 psi and the residual pressure during the test is 21 psi. Compute the measured discharge and the flow available at a 20 psi residual.

Start with the thinking

• Hydrant flow testing uses Q = 29.83 C d²√p with d in inches, p in psi and Q in gpm.
• The 0.54 exponent projects the test to the standard 20 psi residual used for fire-flow ratings.

Step-by-step solution

1. Formula

   $$Q = 29.83\,C\,d^2\sqrt{p}$$

2. Substituting

   $$Q = 29.83(0.97)(4.5)^{2}\sqrt32 = 3,315 gpm$$

3. Formula

   $$Q_{20} = Q_{test}\left(\dfrac{p_s-20}{p_s-p_r}\right)^{0.54}$$

4. Pressure drops

   $$static - 20 = 23 psi; static - residual = 22 psi$$

5. Substituting

   $$Q_{20} = 3,315(23/22)^{0.54} = 3,395 gpm$$

Why the other options are there

• 736.6 gpm (diameter not squared)
• 3,465 gpm (0.54 exponent dropped)

Reference: FE Reference Handbook — Hydraulics → Fire Hydrant Discharging to Atmosphere

A hydrant outlet 2.5 in. in diameter with a coefficient of 0.97 shows a pitot pressure of 34 psi. Static pressure is 68 psi and the residual pressure during the test is 30 psi. Compute the measured discharge and the flow available at a 20 psi residual.

Start with the thinking

• Hydrant flow testing uses Q = 29.83 C d²√p with d in inches, p in psi and Q in gpm.
• The 0.54 exponent projects the test to the standard 20 psi residual used for fire-flow ratings.

Step-by-step solution

1. Formula

   $$Q = 29.83\,C\,d^2\sqrt{p}$$

2. Substituting

   $$Q = 29.83(0.97)(2.5)^{2}\sqrt34 = 1,054 gpm$$

3. Formula

   $$Q_{20} = Q_{test}\left(\dfrac{p_s-20}{p_s-p_r}\right)^{0.54}$$

4. Pressure drops

   $$static - 20 = 48 psi; static - residual = 38 psi$$

5. Substituting

   $$Q_{20} = 1,054(48/38)^{0.54} = 1,196 gpm$$

Why the other options are there

• 421.8 gpm (diameter not squared)
• 1,332 gpm (0.54 exponent dropped)

Reference: FE Reference Handbook — Hydraulics → Fire Hydrant Discharging to Atmosphere

A hydrant outlet 4.5 in. in diameter with a coefficient of 0.90 shows a pitot pressure of 61 psi. Static pressure is 99 psi and the residual pressure during the test is 33 psi. Compute the measured discharge and the flow available at a 20 psi residual.

Start with the thinking

• Hydrant flow testing uses Q = 29.83 C d²√p with d in inches, p in psi and Q in gpm.
• The 0.54 exponent projects the test to the standard 20 psi residual used for fire-flow ratings.

Step-by-step solution

1. Formula

   $$Q = 29.83\,C\,d^2\sqrt{p}$$

2. Substituting

   $$Q = 29.83(0.90)(4.5)^{2}\sqrt61 = 4,246 gpm$$

3. Formula

   $$Q_{20} = Q_{test}\left(\dfrac{p_s-20}{p_s-p_r}\right)^{0.54}$$

4. Pressure drops

   $$static - 20 = 79 psi; static - residual = 66 psi$$

5. Substituting

   $$Q_{20} = 4,246(79/66)^{0.54} = 4,679 gpm$$

Why the other options are there

• 943.6 gpm (diameter not squared)
• 5,082 gpm (0.54 exponent dropped)

Reference: FE Reference Handbook — Hydraulics → Fire Hydrant Discharging to Atmosphere

A hydrant outlet 2.5 in. in diameter with a coefficient of 0.90 shows a pitot pressure of 39 psi. Static pressure is 79 psi and the residual pressure during the test is 35 psi. Compute the measured discharge and the flow available at a 20 psi residual.

Start with the thinking

• Hydrant flow testing uses Q = 29.83 C d²√p with d in inches, p in psi and Q in gpm.
• The 0.54 exponent projects the test to the standard 20 psi residual used for fire-flow ratings.

Step-by-step solution

1. Formula

   $$Q = 29.83\,C\,d^2\sqrt{p}$$

2. Substituting

   $$Q = 29.83(0.90)(2.5)^{2}\sqrt39 = 1,048 gpm$$

3. Formula

   $$Q_{20} = Q_{test}\left(\dfrac{p_s-20}{p_s-p_r}\right)^{0.54}$$

4. Pressure drops

   $$static - 20 = 59 psi; static - residual = 44 psi$$

5. Substituting

   $$Q_{20} = 1,048(59/44)^{0.54} = 1,228 gpm$$

Why the other options are there

• 419.1 gpm (diameter not squared)
• 1,405 gpm (0.54 exponent dropped)

Reference: FE Reference Handbook — Hydraulics → Fire Hydrant Discharging to Atmosphere

A hydrant outlet 4.0 in. in diameter with a coefficient of 0.97 shows a pitot pressure of 34 psi. Static pressure is 59 psi and the residual pressure during the test is 25 psi. Compute the measured discharge and the flow available at a 20 psi residual.

Start with the thinking

• Hydrant flow testing uses Q = 29.83 C d²√p with d in inches, p in psi and Q in gpm.
• The 0.54 exponent projects the test to the standard 20 psi residual used for fire-flow ratings.

Step-by-step solution

1. Formula

   $$Q = 29.83\,C\,d^2\sqrt{p}$$

2. Substituting

   $$Q = 29.83(0.97)(4.0)^{2}\sqrt34 = 2,700 gpm$$

3. Formula

   $$Q_{20} = Q_{test}\left(\dfrac{p_s-20}{p_s-p_r}\right)^{0.54}$$

4. Pressure drops

   $$static - 20 = 39 psi; static - residual = 34 psi$$

5. Substituting

   $$Q_{20} = 2,700(39/34)^{0.54} = 2,907 gpm$$

Why the other options are there

• 674.9 gpm (diameter not squared)
• 3,096 gpm (0.54 exponent dropped)

Reference: FE Reference Handbook — Hydraulics → Fire Hydrant Discharging to Atmosphere

A hydrant outlet 2.5 in. in diameter with a coefficient of 0.80 shows a pitot pressure of 55 psi. Static pressure is 88 psi and the residual pressure during the test is 44 psi. Compute the measured discharge and the flow available at a 20 psi residual.

Start with the thinking

• Hydrant flow testing uses Q = 29.83 C d²√p with d in inches, p in psi and Q in gpm.
• The 0.54 exponent projects the test to the standard 20 psi residual used for fire-flow ratings.

Step-by-step solution

1. Formula

   $$Q = 29.83\,C\,d^2\sqrt{p}$$

2. Substituting

   $$Q = 29.83(0.80)(2.5)^{2}\sqrt55 = 1,106 gpm$$

3. Formula

   $$Q_{20} = Q_{test}\left(\dfrac{p_s-20}{p_s-p_r}\right)^{0.54}$$

4. Pressure drops

   $$static - 20 = 68 psi; static - residual = 44 psi$$

5. Substituting

   $$Q_{20} = 1,106(68/44)^{0.54} = 1,399 gpm$$

Why the other options are there

• 442.5 gpm (diameter not squared)
• 1,709 gpm (0.54 exponent dropped)

Reference: FE Reference Handbook — Hydraulics → Fire Hydrant Discharging to Atmosphere

A hydrant outlet 2.5 in. in diameter with a coefficient of 0.90 shows a pitot pressure of 41 psi. Static pressure is 75 psi and the residual pressure during the test is 42 psi. Compute the measured discharge and the flow available at a 20 psi residual.

Start with the thinking

• Hydrant flow testing uses Q = 29.83 C d²√p with d in inches, p in psi and Q in gpm.
• The 0.54 exponent projects the test to the standard 20 psi residual used for fire-flow ratings.

Step-by-step solution

1. Formula

   $$Q = 29.83\,C\,d^2\sqrt{p}$$

2. Substituting

   $$Q = 29.83(0.90)(2.5)^{2}\sqrt41 = 1,074 gpm$$

3. Formula

   $$Q_{20} = Q_{test}\left(\dfrac{p_s-20}{p_s-p_r}\right)^{0.54}$$

4. Pressure drops

   $$static - 20 = 55 psi; static - residual = 33 psi$$

5. Substituting

   $$Q_{20} = 1,074(55/33)^{0.54} = 1,416 gpm$$

Why the other options are there

• 429.8 gpm (diameter not squared)
• 1,791 gpm (0.54 exponent dropped)

Reference: FE Reference Handbook — Hydraulics → Fire Hydrant Discharging to Atmosphere