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Sprinkler K-factor: flow and pressure
Know two of K, pressure and flow to get the third. US units included to check against catalogues.
Quick answer
A K80 sprinkler (US K5.6) at 1.00 bar discharges 80.0 L/min (21.1 gpm).
Preliminary results
K-factor80.0K5.6 US
Pressure1.00bar · 14.5 psi
Flow80.0L/min · 21.1 gpm
| Step | Result | Basis |
|---|---|---|
| Solve Q = K·√PQ = 80 × √1.00 | 80.0 L/min | Q = K√P |
| US unitsK/14.4 · bar×14,5 · L/min×0,264 | K5.6 · 14.5 psi · 21.1 gpm | NFPA 13 |
Sources and assumptions. Q = K·√P (TCVN 7336:2021, NFPA 13). Metric K = 14.4 × US K; 1 bar = 14.5 psi; 1 L/min = 0.264 gpm. ⚠ = code table value to be checked against the original standard. Preliminary results for material selection and budgeting; not a substitute for an approved fire protection design.
Common sprinkler flows by pressure
| Metric K | US K | 0.5 bar | 1 bar | 2 bar | 3 bar |
|---|---|---|---|---|---|
| K57 | K4.2 | 40 | 57 | 81 | 99 |
| K80 | K5.6 | 57 | 80 | 113 | 139 |
| K115 | K8.0 | 81 | 115 | 163 | 199 |
| K161 | K11.2 | 114 | 161 | 228 | 279 |
| K202 | K14.0 | 143 | 202 | 286 | 350 |
| K242 | K16.8 | 171 | 242 | 342 | 419 |
| K363 | K25.2 | 257 | 363 | 513 | 629 |
Frequently asked questions
How much water does a K80 sprinkler discharge at 1 bar?
Q = 80 × √1 = 80 L/min (about 21 gpm). At 0.5 bar 56.6 L/min; at 2 bar 113 L/min.
What is the difference between K5.6 and K80?
Same sprinkler: K5.6 is in gpm/psi^0.5 (US), K80 in L/min/bar^0.5 (metric). The conversion factor is 14.4.