Sprinkler K Factors
Hydraulics · FE Reference Handbook section
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.
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
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.
Figure 1 — schematic for Sprinkler K Factors — solve for discharge — Sprinkler K Factors
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that Q stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning Q = 88.1816 gpm to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Q:
Step 3 — List the givens: sprinkler K factor (K) = 5.4000 gpm/psi^0.5, residual pressure at the head (P) = 66.5000 psi.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning Q = 44.0357 gpm to
reproduces the given quantities, and both sides carry the same units.
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
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
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.
Figure 3 — schematic for Sprinkler K Factors — solve for sprinkler K-factor — Sprinkler K Factors (3)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that K stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
K = 24.6580\ \text{gpm/psi^0.5}Step 6 — Check: returning K = 24.6580 gpm/psi^0.5 to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for K:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
K = 2.7504\ \text{gpm/psi^0.5}Step 6 — Check: returning K = 2.7504 gpm/psi^0.5 to
reproduces the given quantities, and both sides carry the same units.
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
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
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.
Figure 5 — schematic for Sprinkler K Factors — solve for pressure at sprinkler — Sprinkler K Factors (5)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that P stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning P = 657.2 psi to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 13.2529 psi to
reproduces the given quantities, and both sides carry the same units.
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
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
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.
Figure 7 — schematic for Sprinkler K Factors — solve for discharge (case 2) — Sprinkler K Factors (7)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that Q stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning Q = 33.2265 gpm to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Q:
Step 3 — List the givens: sprinkler K factor (K) = 11.4000 gpm/psi^0.5, residual pressure at the head (P) = 79.5000 psi.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning Q = 101.6 gpm to
reproduces the given quantities, and both sides carry the same units.
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
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
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.
Figure 9 — schematic for Sprinkler K Factors — solve for sprinkler K-factor (case 2) — Sprinkler K Factors (9)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that K stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
K = 40.0047\ \text{gpm/psi^0.5}Step 6 — Check: returning K = 40.0047 gpm/psi^0.5 to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for K:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
K = 21.0507\ \text{gpm/psi^0.5}Step 6 — Check: returning K = 21.0507 gpm/psi^0.5 to
reproduces the given quantities, and both sides carry the same units.
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