Hydrant Flow Test Calculator

The Hydrant Flow Test Calculator measures the rated capacity at 20 psi of a fire hydrant. The rated capacity calculation is useful in determining the total water supply at a given point in the hydrant or water main. The calculation offers more useful information than the test flow by itself and is used by insurance underwriters. For more information see NFPA 291, AWWA M-17, or our web page on Hydrant Flow Testing.

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0 500 1,000 1,500 2,000 2,500 0 10 20 30 40 50 60 70 80 90 100 110 2207 GPM at 20 psi Predicted Flow Rate (GPM) Pressure (PSI)
gpm psi x psi psi
2,535 1 20
2,519 2 20
2,502 3 20
2,486 4 20
2,469 5 20
2,453 6 20
2,436 7 20
2,419 8 20
2,402 9 20
2,385 10 20
2,368 11 20
2,350 12 20
2,333 13 20
2,315 14 20
2,298 15 20
2,280 16 20
2,262 17 20
2,244 18 20
2,226 19 20
2,207 20 20 20
2,189 21 20
2,170 22 20
2,152 23 20
2,133 24 20
2,114 25 20
2,095 26 20
2,076 27 20
2,056 28 20
2,037 29 20
2,017 30 20
1,997 31 20
1,977 32 20
1,957 33 20
1,936 34 20
1,916 35 20
1,895 36 20
1,874 37 20
1,853 38 20
1,831 39 20
1,810 40 20
1,788 41 20
1,766 42 20
1,744 43 20
1,721 44 20
1,698 45 20
1,675 46 20
1,652 47 20
1,628 48 20
1,604 49 20
1,580 50 20
1,556 51 20
1,531 52 20
1,506 53 20
1,480 54 20
1,454 55 20
1,428 56 20
1,401 57 20
1,374 58 20
1,346 59 20
1,318 60 20
1,289 61 20
1,260 62 20
1,230 63 20
1,199 64 20
1,168 65 20
1,136 66 20
1,103 67 20
1,070 68 20
1,035 69 20
1,000 70 20
963 71 20
926 72 20
886 73 20
846 74 20
803 75 20
759 76 20
712 77 20
663 78 20
610 79 20
553 80 20
490 81 20
419 82 20
337 83 20
232 84 20
0 85 20

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