F3 Fire Pumps & Accessories — practice test
F3 is the EVT Fire Apparatus test on the pump itself and everything bolted to it: centrifugal theory, drives and interlocks, priming, pressure control, plumbing, foam, and NFPA 1911 service testing. Techs fail it because they know how to make water on the fireground but not why the pump behaves the way it does, so they answer from operator habit instead of the standard. The other killer is the test's love of two-technician items, where both answers sound right in the bay and only one survives a spec sheet.
Studying for F3 (Fire Pumps & Accessories)? Overhaul Prep has 238 verified F3 questions written to the current task list — in the same formats the real exam uses (direct, Technician A/B, EXCEPT and most-likely-cause). Every answer comes with a written explanation, so you learn why instead of memorising a letter.
What's on the F3 test
F3 covers the pump and its accessories end to end: centrifugal pump theory and hydraulics, pump drive and shift interlocks, priming and drafting, pressure control (mechanical relief valves and electronic governors), plumbing, valves, tanks, gauges, foam and CAFS, plus NFPA 1911 pump service testing. Expect roughly 50 to 60 scored questions with unscored pretest items mixed in. The weight sits heaviest on pressure control, pump theory, and priming/drafting/cavitation. Foam and CAFS is a smaller slice but shows up every time, and testing procedure questions are free points if you memorized the numbers.
High-yield F3 topics
The material that shows up year after year. If you're short on time, start here.
- Pump rating points and the annual service test. A pump is rated at 100 percent capacity at 150 psi, 70 percent at 200 psi, and 50 percent at 250 psi, from draft at 10 ft lift with 20 ft of suction hose. NFPA 1911 runs 20 minutes at the 150 psi point, then 10 minutes each at 200 and 250. Know the dry vacuum test: pull 22 in Hg and lose no more than 10 in Hg in 5 minutes. These exact figures get asked as plain recall.
- Transfer valve logic on a two-stage pump. Parallel (volume) when you are flowing more than 50 percent of rated capacity, series (pressure) when you are below it. Series stacks the impellers so the second stage takes the first stage's discharge, doubling pressure at half the volume. They will also ask when to transfer: at low RPM and low discharge pressure, not under load.
- Cavitation signatures versus everything that looks like it. The tell is engine RPM climbing with no rise in discharge pressure, plus the gravel-in-the-pump rattle and a fluttering discharge gauge. Cause is demanding more water than the supply can deliver, and the fix is throttle back or reduce flow, not open something. Tie it to the lift math: atmospheric limits theoretical lift to about 33.9 ft, practical lift runs about 22 to 25 ft, and 1 in Hg is roughly 1.13 ft.
- Priming systems and their timing spec. Know rotary vane, exhaust ejector, and electric primers as positive displacement devices, and that a pump rated up to 1500 gpm must prime in 30 seconds while 1500 to 2500 gpm gets 45 seconds at 10 ft lift. Failed prime almost always means an air leak on the suction side: intake cap gasket, drain cock, packing pulled too loose, or a valve not seating.
- Pressure control: relief valve versus electronic governor. A pilot-operated relief valve dumps or bypasses water and never touches engine speed. A governor in PSI mode reduces engine RPM to hold discharge pressure. Both must limit pressure rise to no more than 30 psi when discharges are closed, and NFPA has you verify it at 150 psi and at 90 psi. Also know the intake relief (dump) valve, typically preset around 125 psi, is there for water hammer from the supply side.
- Foam proportioning types and their limits. Around-the-pump proportioners rely on a venturi and quit working once inlet pressure gets up near 10 psi, which is why they die on a hydrant. In-line eductors need about 200 psi inlet, a nozzle flow that matches the eductor rating, and a hose limit (commonly 200 ft) between eductor and nozzle. Percentages: Class A 0.1 to 1.0, Class B 3 or 6 percent depending on concentrate and fuel.
Where techs lose points on F3
Good technicians miss these — not from lack of skill, but because the question is built to catch them.
- Packing is supposed to drip. Expect a question where a pump packing gland weeps and the tempting answer is tighten it until it stops. Wrong. It needs roughly 8 to 10 drops per minute at idle to cool and lubricate the shaft sleeve, and cranking it down scores the sleeve and burns the packing. The mirror-image trap: a mechanical seal that drips is not adjustable at all, it gets replaced.
- Around-the-pump foam that 'stops working on a hydrant' is not a bad eductor. Techs read the symptom, see foam concentrate flowing on draft but nothing on a pressurized supply, and pick pickup tube or check valve. The system is working as designed. Positive inlet pressure kills the venturi. Same energy trap: an in-line eductor that foams fine at 150 ft and fails at 300 ft is a hose length problem, not a concentrate problem.
- Relief valve and governor are not interchangeable answers. When the stem says a discharge is shut down and pressure spikes, ask what device is on the truck. If it is a relief valve, engine speed will not change and the answer involves the pilot setting or a stuck valve. If it is a governor in RPM mode, it is doing exactly what it was told to do and the operator left it in the wrong mode. Picking 'governor failed' on an RPM-mode question is a give-away miss.
- Pump shift and interlock questions want the whole chain, not just the green light. The OK to Pump light proves both the pump shift completed and the transmission locked into drive, and the speedometer reading (commonly 10 to 15 mph) confirms the split shaft is turning. A pump shift indicator lit with no speedometer movement is not 'shift complete', and picking the pump shift air cylinder before checking the transmission side is the classic wrong first step.
A study plan that works for F3
Roughly two weeks of real preparation, in the order that actually builds on itself.
- Days 1-3: Pump theory and hydraulics. Centrifugal action, volute and impeller, single versus two-stage, transfer valve logic both directions, net pump pressure from draft, lift math and the in Hg conversions. Do not move on until you can explain in your own words why series doubles pressure and halves volume. This is the foundation the priming and cavitation questions are built on.
- Days 4-6: Priming, drafting, cavitation, and pressure control together. They interlock. Memorize the prime timing specs, the dry vacuum test numbers, and the 30 psi pressure-rise limit. Then drill relief valve versus governor scenarios side by side until you can tell them apart from the symptom alone. This block is the biggest scoring chunk on the test.
- Days 7-8: Plumbing, tanks, valves, gauges, foam and CAFS. Tank-to-pump flow requirements, intake relief, master compound gauge range, auxiliary cooler (water through the exchanger, never mixing with coolant), then foam percentages and the three proportioner families with their limits. Foam is a small slice but it is cheap points because the same three traps repeat.
- Days 9-10: NFPA 1911 service test procedure front to back, in order, with the clock times, plus a full timed practice run. Review every miss by task area, not by question. If you are dropping questions in one area, go back to that block instead of grinding more random practice.
Sample F3 questions
Straight from the bank — answers highlighted, with the explanation underneath.
In a centrifugal fire pump operating at a constant engine (impeller) speed, as the volume of water being discharged increases, the discharge pressure will:
- Decrease
- Increase proportionally with flow
- Remain exactly constant
- Increase and then stabilize
A two-stage (series-parallel) centrifugal pump can be operated in either a volume or a pressure mode using the transfer valve. Technician A says that in the volume (parallel) position, each impeller draws from the intake and discharges together, so the pump's capacity is the sum of both impellers. Technician B says that in the pressure (series) position, the discharge of the first impeller feeds the eye of the second impeller, so the pressures of the two stages add together. Who is correct?
- Technician A only
- Technician B only
- Both Technicians A and B
- Neither Technician
While supplying attack lines from draft, an operator advances the throttle to raise discharge pressure, but the pressure does not climb and a sound like gravel or marbles is heard inside the pump. This condition is MOST likely:
- Normal pressure-governor operation
- Cavitation caused by demanding more water than the supply can deliver
- Water hammer from a suddenly closed valve
- A collapsed tank-to-pump line
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