Fire Hydrants, Nozzles, and Flow Rates Study Notes

Water supply in an urban city is determined by:
- Engine's pumping capacity.
- Available water supply.

High intake pressure (e.g., 420-700 Kpa) from a hydrant results in a higher rated capacity than the manufacturer's specifications, as it avoids drafting from 10' with 20' of suction hose.

NFPA 291 outlines guidelines for hydrant coloring and minimum LPM (Liters Per Minute) each color-top should provide:
- Class AA Hydrants: Blue, > 5700 L/min
- Class A Hydrants: Green, 3800 - 5700 L/min
- Class B Hydrants: Orange, 1900 - 3800 L/min
- Class C Hydrants: Red, < 1900 L/min (typically private hydrants, not reliable for fire service)
Color-coded reflective rings or painted caps indicate flow rate.

Key factors beyond hydrant color that affect expected available water supply:
- Peak Hours
- Number of Discharges
- Supply Hose Utilized

Time of day impacts water supply. "Blue top" hydrant standard (5678 LPM) is set with peak consumption hours in mind.
Peak hours (early morning and late evening) see increased consumer demand (showers, cooking), potentially reducing available volume.

Expected volume from a single hydrant is based on utilizing all discharges (usually 3).

4" LDH (Large Diameter Hose) and 2.5" are primary supply hose options. Hose choice significantly affects water supply due to friction loss.
2.5" hose has significantly more friction loss than 4" LDH.

Multiple Connections from a Hydrant
- Pumps often outperform hydrants; adding supply lines from the same hydrant can maximize volume.
Pumping in Series/ Relay Pumping
- Pumping in series (stacking multiple engines in line, discharge-to-intake) boosts pressure down the line, overcoming friction loss related to volume or distance needs.
- Relay Pumping is pumping in series to overcome distance.
Hydrant Assist Valve (HAV)
- 4-way valve connects directly to the hydrant.
- Primary supply line connects to the front of the HAV, laid towards the structure.
- A second apparatus connects one supply line to their intake and another to their discharge, acting as a supply engine to "pump the hydrant".
- This increases pressure to the attack engine. A one-way clapper valve prevents the supply engine from pressurizing the hydrant.

Static Pressure: Pressure on the pump's intake manifold gauge after hose connection and hydrant opening, before water flow.
Residual Pressure: Pressure on the intake manifold gauge when water is flowing from the discharge manifold.
Operators use the difference between static and residual pressure to determine additional water availability and fire flow to provide to the incident commander.

Compares static pressure to residual pressure to estimate remaining water supply.
Percentage Drop = $\frac{(Static - Residual) \times 100}{Static}$
0-10% drop: Additional 3x current flow available
11-15% drop: Additional 2x current flow available
16-25% drop: Additional 1x current flow available
25%+ drop: No more than current flow available

Calculates the percentage drop in pressure between static and residual pressure to estimate remaining water supply.
Example: 560 KPa static, 420 KPa residual = 25% drop.
0-10% = 3X initial target flow
11-15% = 2X initial target flow
16-25% = Same as initial target flow
In the example above, you would have roughly another 3500 LPM available for firefighting operations

Pump operators must know the flow rate and pressure needed for each nozzle on their truck (hand line, ground monitor, aerial device nozzle).
Figures are printed on nozzles or in manufacturer's documentation.

Pressure impacts hose reach/penetration, ease of use, maneuverability, control, and overall performance.
Incorrect pressure prevents the nozzle from delivering the specified flow rate.
Proper flow and pressure are needed to combat heat release rates (HRR).

Typical 2000 sq ft, two-story single-family home (no basement/exposures): 1140 lpm (300 gpm) from two handlines
Open-air Strip Shopping Center: 1892 lpm (500 gpm) from three handlines
Typical 1200 sq ft apartment (three-story garden style): 1140 lpm (300 gpm) from three handlines
High-Rise (>75 ft): 1892 lpm (500 gpm) from two handlines on the fire floor, 946 lpm (250 gpm) on the floor above the fire
Pump operators should be aware of required flow rate based on fire size and HRR upon arrival.

HANDLINES/HOSE PACK:
- 45 mm FOG: 570 L/min at 350 kPa
- 65 mm FOG: 950 L/min at 350 kPa
- 100 mm SMOOTH BORE: 3800 L/min at 350 kPa
MERCURY MASTER:
- 29mm / 1½" NOZZLE: 1003 L/min at 560 kPa
- 50mm/2" NOZZLE: 3800 L/min at 550 kPa

Service testing ensures hose is maintained in optimum condition and functions under pressure during firefighting.
Guidelines in NFPA 1962: "Standard for the Care, Use, and Service Testing of Fire Hose including Couplings and Nozzles".

Physical inspection checks for debris, mildew, rot, chemical damage, burns, cuts, abrasion, and vermin.
Hose failing inspection is removed from service, repaired/tested, or condemned.

Check hose and gasket for damage (5.5.5)
Connect test gate valve (if required), hose sections, and nozzle/shut-off valve using a spanner wrench (5.5.5 (B-1))
Notify pump operator to fill and pressurize each hose line to 350 kPa (50 psi) or hydrant pressure (5.5.5)
Open nozzle/valve above pump discharge to bleed air from the line (5.5.5 (B-1))
Mark the hose against the coupling with chalk/pencil (5.5.5 (B-1))
Close test gate valve and notify pump operator to increase pressure to test pressure per NFPA 1962 (2070 kPa / 300 psi for attack hose) (5.5.5 (B-1))
Check connections for leakage as pressure increases (5.5.5)
Check hose jacket and couplings for damage/leakage, maintaining test pressure for 3 minutes (5.5.5)
Notify pump operator to slowly reduce pressure, close each discharge valve, and disengage pump (5.5.5 (B-1))
Open nozzle to bleed off pressure and disconnect all couplings (5.5.5 (B-1))
Check marks on the hose to ensure coupling did not move, and notify an Officer (Evaluator) of the test results (5.5.5 (B-1))