NFPA D/O Mobile Water Supply key terms

A documented walk-around check of tires, brakes, lights, fluid levels, pump engagement, and tank integrity performed before a mobile water supply unit responds, confirming the apparatus is roadworthy and ready to pump or dump.

The verified condition in which an apparatus, its pump, tank, and discharge equipment are fueled, filled, tested, and staffed so it can perform its assigned water supply function without delay at an incident.

A scheduled evaluation of a fire pump at rated capacity, pressure, and overload conditions to confirm it still delivers its rated flow, typically required at least yearly and after major pump repair.

Conditions such as cracked brake drums, inoperative warning lights, low tire tread, or a failed pump test that make an apparatus unsafe or unable to perform and require it to be removed from response status.

A driving strategy that assumes other motorists may not see or yield to the apparatus, so the operator controls speed, following distance, and lane position to allow a safe stop or evasive action.

The conditional privilege granted to an authorized emergency vehicle using warning lights and siren, which still requires the driver to drive with due regard for others and does not excuse reckless operation.

The legal standard requiring an emergency vehicle operator to consider the safety of all persons on the road while responding, so the right-of-way privilege is lost when driving is reckless or careless.

The gap maintained behind the vehicle ahead, commonly measured in seconds by counting to a fixed roadside object, giving the heavy, water-laden apparatus room to stop on slippery or downhill grades.

The danger that a high-center-of-gravity tanker will overturn during sharp turns, off-road travel, or sudden evasive steering, worsened when the tank is full or the load shifts because of missing baffles.

A person positioned outside the apparatus who guides the driver during backing, tight maneuvering, or positioning at a fill or dump site using agreed hand signals and radio contact.

A controlled sequence in which the driver stops, sets the brake, uses a spotter or rear camera, backs slowly, and stops immediately if visual or radio contact with the guide is lost.

The flow in gallons per minute that a pump is certified to deliver at a stated pressure, such as 1,000 gpm at 150 psi, and the basis for predicting performance in relay and shuttle planning.

The total pressure the pump actually adds to the water, calculated as the discharge pressure minus the intake pressure, used to compare pump performance against its rating.

Pressure lost as water moves through hose, pipe, and fittings because of turbulence and contact with the walls, increasing with higher flow and longer hose lays and reducing the pressure available at the nozzle.

The pressure measured on the suction or incoming side of the pump, which must stay positive enough to prevent cavitation while not exceeding the pump's safe inlet limit.

Damage and performance loss caused when pressure at the pump impeller eye drops so low that water vaporizes and bubbles collapse, producing a rattling sound, reduced flow, and possible impeller damage.

A device that opens to release excess pressure from the pump or discharge piping, protecting hose and crews when a nozzle shuts down suddenly or intake pressure rises unexpectedly.

An internal wall inside a water tank that divides the liquid into compartments to slow front-to-back and side-to-side movement, reducing surge forces on the chassis and driver.

The shifting mass of water inside a partially filled tank that moves forward, backward, or sideways as the apparatus accelerates, brakes, or turns, producing forces that can push the vehicle off course.

A large-diameter valve, often air or electric operated, at the rear or side of the tank that opens to release the full load quickly into a portable tank or water source.

A collapsible fabric tank set on level ground at a dump site to receive water from arriving tenders, allowing a pumper to draft continuously while tenders cycle back to the fill site.

A design feature allowing the apparatus to discharge water from its pump while the vehicle is moving slowly, so it can begin emptying before stopping and shorten turnaround time.

A rapid unloading method in which a small pump or residual pressure pushes water through the dump valve faster than gravity alone, shortening the time the tender sits at the dump site.

A location with a reliable water source, suitable access, and a pumper or hydrant arranged so arriving tenders can be loaded quickly and released without blocking each other.

Drawing water from a static source such as a pond, pool, or portable tank by creating a partial vacuum with the pump, using hard suction hose with airtight connections.

A rigid, non-collapsing hose used on the intake side of a pump so that atmospheric pressure can push water into the pump without the hose flattening under vacuum.

The location where tenders unload into a portable tank or directly to a pumper, chosen for level firm ground, safe entry and exit, and enough space for multiple apparatus to maneuver.

The process of choosing an unloading location based on road access, turning radius, ground bearing strength, distance to the fire, and room for tenders to queue and leave without conflict.

A transport system in which tenders repeatedly load at a fill site, travel a route, unload at a dump site, and return, delivering water to an area without adequate supply.

The total time a tender spends completing one shuttle cycle, including loading, travel to the dump site, unloading, and the return trip, which determines how many tenders are needed.

The planning step that divides total water delivered by elapsed time, or multiplies tender tank size by the number of trips per hour, to estimate whether the shuttle meets the fireground demand.

Moving water long distances through a series of pumpers connected by hose, each adding pressure so the flow reaches the fireground without exceeding hose pressure limits.

Operating two pumps together so that one discharges into the intake of the next, increasing total pressure or volume while each pump is monitored to avoid overpressurizing the receiving pump.

A standardized management structure that assigns clear roles for water supply, staging, and safety, allowing the shuttle or relay to be coordinated as one component of the overall incident.

The person assigned to plan, request, and manage fill sites, dump sites, tenders, and relay pumpers, tracking delivered flow and adjusting the operation as fireground demand changes.

A designated location where uncommitted apparatus waits under a staging officer, keeping access routes clear and allowing tenders to be dispatched to fill or dump sites in an orderly sequence.

The practice of keeping transmissions brief, using clear text and assigned channels, and avoiding unnecessary traffic so that critical water supply orders and safety warnings get through.