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Sprinkler K Factors

Hydraulics · FE Reference Handbook section

Hydraulics
29 formulas
10 exam-style examples
~60 min
All Hydraulics lectures

Handbook notes for this section

Definitions and conditions exactly as the handbook states them.

  • Orifice Size Name K Factor
  • Queueing models are found in the Industrial Engineering section.
  • PHF Hourly Flow Rate 4 * V15

Core formulas for this FE topic

Definitions, applicability, units, assumptions and worked examples for each relation.

Worked exam-style examples

The four ways this section is written on the real exam — thoughts first, then equations, then substitution.

Example 1
Sprinkler K Factors — solve for discharge — Sprinkler K Factors

sprinkler K factors used to size a fire protection sprinkler head Given sprinkler K-factor (K) = 18.0000 gpm/psi^0.5; pressure at sprinkler (P) = 24.0000 psi, determine the discharge (Q) in gpm.

Given

  • sprinklerK−factor(K)=18.0000gpm/psi0.5sprinkler K-factor (K) = 18.0000 gpm/psi^0.5
  • pressureatsprinkler(P)=24.0000psipressure at sprinkler (P) = 24.0000 psi

Find

discharge (Q), in gpm

Start with the thinking

  • The governing relation printed in this handbook section is Sprinkler K Factors.
  • Everything except Q is given, so isolate Q symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Sprinkler K factors relate the discharge of a fire sprinkler head to the pressure at its orifice.
D₁=25D₂=25risersprinkler

Figure 1 — schematic for Sprinkler K Factors — solve for discharge — Sprinkler K Factors

Step-by-step solution

  1. Step 1 — State the governing relation:

    Q=KPQ = K \sqrt{P}
  2. Step 2 — Rearrange the relation so that Q stands alone on the left-hand side.

  3. Step 3

    Listthegivens:sprinklerK−factor(K)=18.0000gpm/psi0.5,pressureatsprinkler(P)=24.0000psiList the givens: sprinkler K-factor (K) = 18.0000 gpm/psi^0.5, pressure at sprinkler (P) = 24.0000 psi
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    Q=88.1816 gpmQ = 88.1816\ \text{gpm}
  6. Step 6 — Check: returning Q = 88.1816 gpm to

    Q=KPQ = K \sqrt{P}

    reproduces the given quantities, and both sides carry the same units.

Answer:
Q=88.1816 gpmQ = 88.1816\ \text{gpm}

Why the other options are there

  • 176.4 — kept a factor of two that cancels in the correct rearrangement.
  • 44.0908 — dropped that same factor in the other direction.
  • 96.9998 — rounded an intermediate value before the final step.

Reference: FE Handbook — Sprinkler K Factors

Example 2
Sprinkler discharge from the K factor — solve for discharge — Sprinkler K Factors (2)

an upright sprinkler protecting a parking structure Given sprinkler K factor (K) = 5.4000 gpm/psi^0.5; residual pressure at the head (P) = 66.5000 psi, determine the discharge (Q) in gpm.

Given

  • sprinklerKfactor(K)=5.4000gpm/psi0.5sprinkler K factor (K) = 5.4000 gpm/psi^0.5
  • residualpressureatthehead(P)=66.5000psiresidual pressure at the head (P) = 66.5000 psi

Find

discharge (Q), in gpm

Start with the thinking

  • The governing relation printed in this handbook section is Sprinkler discharge from the K factor.
  • Everything except Q is given, so isolate Q symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • A fire-protection sprinkler head discharges under the residual pressure at the head.

Step-by-step solution

  1. Step 1 — State the governing relation:

    Q=KPQ = K \sqrt{P}
  2. Step 2 — Rearrange symbolically for Q:

    Q=KPQ = K \sqrt{P}
  3. Step 3 — List the givens: sprinkler K factor (K) = 5.4000 gpm/psi^0.5, residual pressure at the head (P) = 66.5000 psi.

  4. Step 4 — Substitute the given values:

    Q=5.400066.5000Q = 5.4000 \sqrt{66.5000}
  5. Step 5 — Evaluate:

    Q=44.0357 gpmQ = 44.0357\ \text{gpm}
  6. Step 6 — Check: returning Q = 44.0357 gpm to

    Q=KPQ = K \sqrt{P}

    reproduces the given quantities, and both sides carry the same units.

Answer:
Q=44.0357 gpmQ = 44.0357\ \text{gpm}

Why the other options are there

  • 88.0713 — kept a factor of two that cancels in the correct rearrangement.
  • 22.0178 — dropped that same factor in the other direction.
  • 48.4392 — rounded an intermediate value before the final step.

Reference: FE Handbook — Sprinkler K Factors

Example 3
Sprinkler K Factors — solve for sprinkler K-factor — Sprinkler K Factors (3)

sprinkler K factors for a standard-response sprinkler in a piping design Given pressure at sprinkler (P) = 60.0000 psi; discharge (Q) = 191.0 gpm, determine the sprinkler K-factor (K) in gpm/psi^0.5.

Given

  • pressureatsprinkler(P)=60.0000psipressure at sprinkler (P) = 60.0000 psi
  • discharge(Q)=191.0gpmdischarge (Q) = 191.0 gpm

Find

sprinkler K-factor (K), in gpm/psi^0.5

Start with the thinking

  • The governing relation printed in this handbook section is Sprinkler K Factors.
  • Everything except K is given, so isolate K symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Sprinkler K factors relate the discharge of a fire sprinkler head to the pressure at its orifice.
D₁=25D₂=25risersprinkler

Figure 3 — schematic for Sprinkler K Factors — solve for sprinkler K-factor — Sprinkler K Factors (3)

Step-by-step solution

  1. Step 1 — State the governing relation:

    Q=KPQ = K \sqrt{P}
  2. Step 2 — Rearrange the relation so that K stands alone on the left-hand side.

  3. Step 3

    Listthegivens:pressureatsprinkler(P)=60.0000psi,discharge(Q)=191.0gpmList the givens: pressure at sprinkler (P) = 60.0000 psi, discharge (Q) = 191.0 gpm
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    K = 24.6580\ \text{gpm/psi^0.5}
  6. Step 6 — Check: returning K = 24.6580 gpm/psi^0.5 to

    Q=KPQ = K \sqrt{P}

    reproduces the given quantities, and both sides carry the same units.

Answer:
K = 24.6580\ \text{gpm/psi^0.5}

Why the other options are there

  • 49.3160 — kept a factor of two that cancels in the correct rearrangement.
  • 12.3290 — dropped that same factor in the other direction.
  • 27.1238 — rounded an intermediate value before the final step.

Reference: FE Handbook — Sprinkler K Factors

Example 4
Sprinkler discharge from the K factor — solve for sprinkler K factor — Sprinkler K Factors (4)

a sidewall sprinkler on a corridor main Given discharge (Q) = 24.6000 gpm; residual pressure at the head (P) = 80.0000 psi, determine the sprinkler K factor (K) in gpm/psi^0.5.

Given

  • discharge(Q)=24.6000gpmdischarge (Q) = 24.6000 gpm
  • residualpressureatthehead(P)=80.0000psiresidual pressure at the head (P) = 80.0000 psi

Find

sprinkler K factor (K), in gpm/psi^0.5

Start with the thinking

  • The governing relation printed in this handbook section is Sprinkler discharge from the K factor.
  • Everything except K is given, so isolate K symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • A fire-protection sprinkler head discharges under the residual pressure at the head.

Step-by-step solution

  1. Step 1 — State the governing relation:

    Q=KPQ = K \sqrt{P}
  2. Step 2 — Rearrange symbolically for K:

    K=QPK = \dfrac{Q}{\sqrt{P}}
  3. Step 3

    Listthegivens:discharge(Q)=24.6000gpm,residualpressureatthehead(P)=80.0000psiList the givens: discharge (Q) = 24.6000 gpm, residual pressure at the head (P) = 80.0000 psi
  4. Step 4 — Substitute the given values:

    K=24.600080.0000K = \dfrac{24.6000}{\sqrt{80.0000}}
  5. Step 5 — Evaluate:

    K = 2.7504\ \text{gpm/psi^0.5}
  6. Step 6 — Check: returning K = 2.7504 gpm/psi^0.5 to

    Q=KPQ = K \sqrt{P}

    reproduces the given quantities, and both sides carry the same units.

Answer:
K = 2.7504\ \text{gpm/psi^0.5}

Why the other options are there

  • 5.5007 — kept a factor of two that cancels in the correct rearrangement.
  • 1.3752 — dropped that same factor in the other direction.
  • 3.0254 — rounded an intermediate value before the final step.

Reference: FE Handbook — Sprinkler K Factors

Example 5
Sprinkler K Factors — solve for pressure at sprinkler — Sprinkler K Factors (5)

sprinkler K factors used to verify discharge in a hydraulic calculation Given sprinkler K-factor (K) = 5.5000 gpm/psi^0.5; discharge (Q) = 141.0 gpm, determine the pressure at sprinkler (P) in psi.

Given

  • sprinklerK−factor(K)=5.5000gpm/psi0.5sprinkler K-factor (K) = 5.5000 gpm/psi^0.5
  • discharge(Q)=141.0gpmdischarge (Q) = 141.0 gpm

Find

pressure at sprinkler (P), in psi

Start with the thinking

  • The governing relation printed in this handbook section is Sprinkler K Factors.
  • Everything except P is given, so isolate P symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Sprinkler K factors relate the discharge of a fire sprinkler head to the pressure at its orifice.
D₁=25D₂=25risersprinkler

Figure 5 — schematic for Sprinkler K Factors — solve for pressure at sprinkler — Sprinkler K Factors (5)

Step-by-step solution

  1. Step 1 — State the governing relation:

    Q=KPQ = K \sqrt{P}
  2. Step 2 — Rearrange the relation so that P stands alone on the left-hand side.

  3. Step 3

    Listthegivens:sprinklerK−factor(K)=5.5000gpm/psi0.5,discharge(Q)=141.0gpmList the givens: sprinkler K-factor (K) = 5.5000 gpm/psi^0.5, discharge (Q) = 141.0 gpm
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    P=657.2 psiP = 657.2\ \text{psi}
  6. Step 6 — Check: returning P = 657.2 psi to

    Q=KPQ = K \sqrt{P}

    reproduces the given quantities, and both sides carry the same units.

Answer:
P=657.2 psiP = 657.2\ \text{psi}

Why the other options are there

  • 1,314 — kept a factor of two that cancels in the correct rearrangement.
  • 328.6 — dropped that same factor in the other direction.
  • 722.9 — rounded an intermediate value before the final step.

Reference: FE Handbook — Sprinkler K Factors

Example 6
Sprinkler discharge from the K factor — solve for residual pressure at the head — Sprinkler K Factors (6)

a pendent sprinkler on a warehouse branch line Given discharge (Q) = 32.4000 gpm; sprinkler K factor (K) = 8.9000 gpm/psi^0.5, determine the residual pressure at the head (P) in psi.

Given

  • discharge(Q)=32.4000gpmdischarge (Q) = 32.4000 gpm
  • sprinklerKfactor(K)=8.9000gpm/psi0.5sprinkler K factor (K) = 8.9000 gpm/psi^0.5

Find

residual pressure at the head (P), in psi

Start with the thinking

  • The governing relation printed in this handbook section is Sprinkler discharge from the K factor.
  • Everything except P is given, so isolate P symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • A fire-protection sprinkler head discharges under the residual pressure at the head.

Step-by-step solution

  1. Step 1 — State the governing relation:

    Q=KPQ = K \sqrt{P}
  2. Step 2 — Rearrange symbolically for P:

    P=(QK)2P = \left(\dfrac{Q}{K}\right)^2
  3. Step 3

    Listthegivens:discharge(Q)=32.4000gpm,sprinklerKfactor(K)=8.9000gpm/psi0.5List the givens: discharge (Q) = 32.4000 gpm, sprinkler K factor (K) = 8.9000 gpm/psi^0.5
  4. Step 4 — Substitute the given values:

    P=(32.40008.9000)2P = \left(\dfrac{32.4000}{8.9000}\right)^2
  5. Step 5 — Evaluate:

    P=13.2529 psiP = 13.2529\ \text{psi}
  6. Step 6 — Check: returning P = 13.2529 psi to

    Q=KPQ = K \sqrt{P}

    reproduces the given quantities, and both sides carry the same units.

Answer:
P=13.2529 psiP = 13.2529\ \text{psi}

Why the other options are there

  • 26.5057 — kept a factor of two that cancels in the correct rearrangement.
  • 6.6264 — dropped that same factor in the other direction.
  • 14.5782 — rounded an intermediate value before the final step.

Reference: FE Handbook — Sprinkler K Factors

Example 7
Sprinkler K Factors — solve for discharge (case 2) — Sprinkler K Factors (7)

sprinkler K factors used to size a fire protection sprinkler head Given sprinkler K-factor (K) = 4.0000 gpm/psi^0.5; pressure at sprinkler (P) = 69.0000 psi, determine the discharge (Q) in gpm.

Given

  • sprinklerK−factor(K)=4.0000gpm/psi0.5sprinkler K-factor (K) = 4.0000 gpm/psi^0.5
  • pressureatsprinkler(P)=69.0000psipressure at sprinkler (P) = 69.0000 psi

Find

discharge (Q), in gpm

Start with the thinking

  • The governing relation printed in this handbook section is Sprinkler K Factors.
  • Everything except Q is given, so isolate Q symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Sprinkler K factors relate the discharge of a fire sprinkler head to the pressure at its orifice.
D₁=25D₂=25risersprinkler

Figure 7 — schematic for Sprinkler K Factors — solve for discharge (case 2) — Sprinkler K Factors (7)

Step-by-step solution

  1. Step 1 — State the governing relation:

    Q=KPQ = K \sqrt{P}
  2. Step 2 — Rearrange the relation so that Q stands alone on the left-hand side.

  3. Step 3

    Listthegivens:sprinklerK−factor(K)=4.0000gpm/psi0.5,pressureatsprinkler(P)=69.0000psiList the givens: sprinkler K-factor (K) = 4.0000 gpm/psi^0.5, pressure at sprinkler (P) = 69.0000 psi
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    Q=33.2265 gpmQ = 33.2265\ \text{gpm}
  6. Step 6 — Check: returning Q = 33.2265 gpm to

    Q=KPQ = K \sqrt{P}

    reproduces the given quantities, and both sides carry the same units.

Answer:
Q=33.2265 gpmQ = 33.2265\ \text{gpm}

Why the other options are there

  • 66.4530 — kept a factor of two that cancels in the correct rearrangement.
  • 16.6132 — dropped that same factor in the other direction.
  • 36.5491 — rounded an intermediate value before the final step.

Reference: FE Handbook — Sprinkler K Factors

Example 8
Sprinkler discharge from the K factor — solve for discharge (case 2) — Sprinkler K Factors (8)

an upright sprinkler protecting a parking structure Given sprinkler K factor (K) = 11.4000 gpm/psi^0.5; residual pressure at the head (P) = 79.5000 psi, determine the discharge (Q) in gpm.

Given

  • sprinklerKfactor(K)=11.4000gpm/psi0.5sprinkler K factor (K) = 11.4000 gpm/psi^0.5
  • residualpressureatthehead(P)=79.5000psiresidual pressure at the head (P) = 79.5000 psi

Find

discharge (Q), in gpm

Start with the thinking

  • The governing relation printed in this handbook section is Sprinkler discharge from the K factor.
  • Everything except Q is given, so isolate Q symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • A fire-protection sprinkler head discharges under the residual pressure at the head.

Step-by-step solution

  1. Step 1 — State the governing relation:

    Q=KPQ = K \sqrt{P}
  2. Step 2 — Rearrange symbolically for Q:

    Q=KPQ = K \sqrt{P}
  3. Step 3 — List the givens: sprinkler K factor (K) = 11.4000 gpm/psi^0.5, residual pressure at the head (P) = 79.5000 psi.

  4. Step 4 — Substitute the given values:

    Q=11.400079.5000Q = 11.4000 \sqrt{79.5000}
  5. Step 5 — Evaluate:

    Q=101.6 gpmQ = 101.6\ \text{gpm}
  6. Step 6 — Check: returning Q = 101.6 gpm to

    Q=KPQ = K \sqrt{P}

    reproduces the given quantities, and both sides carry the same units.

Answer:
Q=101.6 gpmQ = 101.6\ \text{gpm}

Why the other options are there

  • 203.3 — kept a factor of two that cancels in the correct rearrangement.
  • 50.8228 — dropped that same factor in the other direction.
  • 111.8 — rounded an intermediate value before the final step.

Reference: FE Handbook — Sprinkler K Factors

Example 9
Sprinkler K Factors — solve for sprinkler K-factor (case 2) — Sprinkler K Factors (9)

sprinkler K factors for a standard-response sprinkler in a piping design Given pressure at sprinkler (P) = 66.0000 psi; discharge (Q) = 325.0 gpm, determine the sprinkler K-factor (K) in gpm/psi^0.5.

Given

  • pressureatsprinkler(P)=66.0000psipressure at sprinkler (P) = 66.0000 psi
  • discharge(Q)=325.0gpmdischarge (Q) = 325.0 gpm

Find

sprinkler K-factor (K), in gpm/psi^0.5

Start with the thinking

  • The governing relation printed in this handbook section is Sprinkler K Factors.
  • Everything except K is given, so isolate K symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Sprinkler K factors relate the discharge of a fire sprinkler head to the pressure at its orifice.
D₁=25D₂=25risersprinkler

Figure 9 — schematic for Sprinkler K Factors — solve for sprinkler K-factor (case 2) — Sprinkler K Factors (9)

Step-by-step solution

  1. Step 1 — State the governing relation:

    Q=KPQ = K \sqrt{P}
  2. Step 2 — Rearrange the relation so that K stands alone on the left-hand side.

  3. Step 3

    Listthegivens:pressureatsprinkler(P)=66.0000psi,discharge(Q)=325.0gpmList the givens: pressure at sprinkler (P) = 66.0000 psi, discharge (Q) = 325.0 gpm
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    K = 40.0047\ \text{gpm/psi^0.5}
  6. Step 6 — Check: returning K = 40.0047 gpm/psi^0.5 to

    Q=KPQ = K \sqrt{P}

    reproduces the given quantities, and both sides carry the same units.

Answer:
K = 40.0047\ \text{gpm/psi^0.5}

Why the other options are there

  • 80.0095 — kept a factor of two that cancels in the correct rearrangement.
  • 20.0024 — dropped that same factor in the other direction.
  • 44.0052 — rounded an intermediate value before the final step.

Reference: FE Handbook — Sprinkler K Factors

Example 10
Sprinkler discharge from the K factor — solve for sprinkler K factor (case 2) — Sprinkler K Factors (10)

a sidewall sprinkler on a corridor main Given discharge (Q) = 178.0 gpm; residual pressure at the head (P) = 71.5000 psi, determine the sprinkler K factor (K) in gpm/psi^0.5.

Given

  • discharge(Q)=178.0gpmdischarge (Q) = 178.0 gpm
  • residualpressureatthehead(P)=71.5000psiresidual pressure at the head (P) = 71.5000 psi

Find

sprinkler K factor (K), in gpm/psi^0.5

Start with the thinking

  • The governing relation printed in this handbook section is Sprinkler discharge from the K factor.
  • Everything except K is given, so isolate K symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • A fire-protection sprinkler head discharges under the residual pressure at the head.

Step-by-step solution

  1. Step 1 — State the governing relation:

    Q=KPQ = K \sqrt{P}
  2. Step 2 — Rearrange symbolically for K:

    K=QPK = \dfrac{Q}{\sqrt{P}}
  3. Step 3

    Listthegivens:discharge(Q)=178.0gpm,residualpressureatthehead(P)=71.5000psiList the givens: discharge (Q) = 178.0 gpm, residual pressure at the head (P) = 71.5000 psi
  4. Step 4 — Substitute the given values:

    K=178.071.5000K = \dfrac{178.0}{\sqrt{71.5000}}
  5. Step 5 — Evaluate:

    K = 21.0507\ \text{gpm/psi^0.5}
  6. Step 6 — Check: returning K = 21.0507 gpm/psi^0.5 to

    Q=KPQ = K \sqrt{P}

    reproduces the given quantities, and both sides carry the same units.

Answer:
K = 21.0507\ \text{gpm/psi^0.5}

Why the other options are there

  • 42.1014 — kept a factor of two that cancels in the correct rearrangement.
  • 10.5254 — dropped that same factor in the other direction.
  • 23.1558 — rounded an intermediate value before the final step.

Reference: FE Handbook — Sprinkler K Factors

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