Hydrant Available Water
Read the intake gauge twice — static, then flowing — and the drop tells you how much more the hydrant has to give. Pairs with the Fire Flow calculator: that one estimates demand, this one estimates supply.
Intake reading connected to the hydrant, no water flowing.
Intake reading while your line is flowing.
Enter values above to see the result.
Percentage-method bands
| Pressure drop | Additional like flows |
|---|---|
| ≤ 10% | 3× |
| > 10% to ≤ 15% | 2× |
| > 15% to ≤ 25% | 1× |
| >25% | 0× |
Pitot flow (hydrant flow test)
Reading a pitot gauge at a flowing outlet? Convert it to GPM here, then use that number as the "current flow" above to estimate what the hydrant still has.
2.5 for a standard hydrant butt; 4 or 4.5 for a steamer.
Enter values above to see the result.
See it live: connect the hydrant on the pump panel and watch the intake gauge drop as you open lines. Open the pump panel