Fire Sprinkler Discharge
Hydraulics · FE Reference Handbook section
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.
a pendent sprinkler on a warehouse branch line Given sprinkler K factor (K) = 10.3000 gpm/psi^0.5; residual pressure at the head (P) = 63.0000 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 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) = 10.3000 gpm/psi^0.5, residual pressure at the head (P) = 63.0000 psi.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning Q = 81.7537 gpm to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 163.5 — kept a factor of two that cancels in the correct rearrangement.
- 40.8769 — dropped that same factor in the other direction.
- 89.9291 — rounded an intermediate value before the final step.
Reference: FE Handbook — Sprinkler K Factors
an upright sprinkler protecting a parking structure Given discharge (Q) = 106.6 gpm; residual pressure at the head (P) = 37.5000 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 = 17.4077\ \text{gpm/psi^0.5}Step 6 — Check: returning K = 17.4077 gpm/psi^0.5 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 34.8154 — kept a factor of two that cancels in the correct rearrangement.
- 8.7039 — dropped that same factor in the other direction.
- 19.1485 — rounded an intermediate value before the final step.
Reference: FE Handbook — Sprinkler K Factors
a sidewall sprinkler on a corridor main Given discharge (Q) = 134.9 gpm; sprinkler K factor (K) = 13.5000 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 = 99.8519 psi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 199.7 — kept a factor of two that cancels in the correct rearrangement.
- 49.9260 — dropped that same factor in the other direction.
- 109.8 — rounded an intermediate value before the final step.
Reference: FE Handbook — Sprinkler K Factors
a pendent sprinkler on a warehouse branch line Given sprinkler K factor (K) = 5.7000 gpm/psi^0.5; residual pressure at the head (P) = 18.5000 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) = 5.7000 gpm/psi^0.5, residual pressure at the head (P) = 18.5000 psi.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning Q = 24.5166 gpm to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 49.0333 — kept a factor of two that cancels in the correct rearrangement.
- 12.2583 — dropped that same factor in the other direction.
- 26.9683 — rounded an intermediate value before the final step.
Reference: FE Handbook — Sprinkler K Factors
an upright sprinkler protecting a parking structure Given discharge (Q) = 181.5 gpm; residual pressure at the head (P) = 67.5000 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 = 22.0915\ \text{gpm/psi^0.5}Step 6 — Check: returning K = 22.0915 gpm/psi^0.5 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 44.1830 — kept a factor of two that cancels in the correct rearrangement.
- 11.0457 — dropped that same factor in the other direction.
- 24.3006 — rounded an intermediate value before the final step.
Reference: FE Handbook — Sprinkler K Factors
a sidewall sprinkler on a corridor main Given discharge (Q) = 37.7000 gpm; sprinkler K factor (K) = 6.2000 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 = 36.9742 psi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 73.9485 — kept a factor of two that cancels in the correct rearrangement.
- 18.4871 — dropped that same factor in the other direction.
- 40.6717 — rounded an intermediate value before the final step.
Reference: FE Handbook — Sprinkler K Factors
a pendent sprinkler on a warehouse branch line Given sprinkler K factor (K) = 6.3000 gpm/psi^0.5; residual pressure at the head (P) = 88.5000 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) = 6.3000 gpm/psi^0.5, residual pressure at the head (P) = 88.5000 psi.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning Q = 59.2669 gpm to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 118.5 — kept a factor of two that cancels in the correct rearrangement.
- 29.6334 — dropped that same factor in the other direction.
- 65.1936 — rounded an intermediate value before the final step.
Reference: FE Handbook — Sprinkler K Factors
an upright sprinkler protecting a parking structure Given discharge (Q) = 178.9 gpm; residual pressure at the head (P) = 53.5000 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 = 24.4587\ \text{gpm/psi^0.5}Step 6 — Check: returning K = 24.4587 gpm/psi^0.5 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 48.9174 — kept a factor of two that cancels in the correct rearrangement.
- 12.2294 — dropped that same factor in the other direction.
- 26.9046 — rounded an intermediate value before the final step.
Reference: FE Handbook — Sprinkler K Factors
a sidewall sprinkler on a corridor main Given discharge (Q) = 98.3000 gpm; sprinkler K factor (K) = 8.6000 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 = 130.7 psi to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 261.3 — kept a factor of two that cancels in the correct rearrangement.
- 65.3251 — dropped that same factor in the other direction.
- 143.7 — rounded an intermediate value before the final step.
Reference: FE Handbook — Sprinkler K Factors
a pendent sprinkler on a warehouse branch line Given sprinkler K factor (K) = 12.7000 gpm/psi^0.5; residual pressure at the head (P) = 14.0000 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 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) = 12.7000 gpm/psi^0.5, residual pressure at the head (P) = 14.0000 psi.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning Q = 47.5190 gpm to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 95.0381 — kept a factor of two that cancels in the correct rearrangement.
- 23.7595 — dropped that same factor in the other direction.
- 52.2710 — rounded an intermediate value before the final step.
Reference: FE Handbook — Sprinkler K Factors