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FAQ Backflow

ANSWER: Backflow is the undesirable reversal of flow of non-potable water or other substances through a cross-connection and into the piping of a public water system or consumer's potable water system. There are two types of backflow... backpressure backflow and backsiphonage.

ANSWER: Backflow into a public water system can pollute or contaminate the water in that system (i.e., backflow into a public water system can make the water in that system unusable or unsafe to drink), and each water supplier has a responsibility to provide water that is usable and safe to drink under all foreseeable circumstances. Furthermore, consumers generally have absolute faith that water delivered to them through a public water system is always safe to drink. For these reasons, each water supplier must take reasonable precautions to protect its public water system against backflow.

ANSWER: Water suppliers usually do not have the authority or capability to repeatedly inspect every consumer's premises for cross-connections and backflow protection. Alteratively, each water supplier should ensure that a proper backflow preventer is installed and maintained at the water service connection to each system or premises that poses a significant hazard to the public water system. Generally, this would include the water service connection to each dedicated fire protection system or irrigation piping system and the water service connection to each of the following types of premises: (I ) premises with an auxiliary or reclaimed water system: (2) industrial, medical, laboratory, marine or other facilities where objectionable substances are handled in a way that could cause pollution or contamination of the public water system; (3) premises exempt from the State Plumbing Code and premises where an internal backflow preventer required under the State Plumbing Code is not properly installed or maintained; (4) classified or restricted facilities; and (5) tall buildings. Each water supplier should also ensure that a proper backflow preventer is installed and maintained at each water loading station owned or operated by the water supplier.

ANSWER: A backflow preventer is a means or mechanism to prevent backflow. The basic means of preventing backflow is an air gap, which either eliminates a cross-connection or provides a barrier to backflow. The basic mechanism for preventing backflow is a mechanical backflow preventer, which provides a physical barrier to backflow. The principal types of mechanical backflow preventer are the reduced-pressure principle assembly, the pressure vacuum breaker assembly, and the double check valve assembly. A secondary type of mechanical backflow preventer is the residential dual check valve.

ANSWER: Mechanical backflow preventers have internal seals, springs, and moving parts that are subject to fouling, wear, or fatigue. Also, mechanical backflow preventers and air gaps can be bypassed. Therefore, all backflow preventers have to be tested periodically to ensure that they are functioning properly. A visual check of air gaps is sufficient, but mechanical backflow preventers have to be tested with properly calibrated gauge equipment.

ANSWER: Backpressure backflow is backflow caused by a downstream pressure that is greater than the upstream or supply pressure in a public water system or consumer's potable water system. Backpressure (i.e., downstream pressure that is greater than the potable water supply pressure) can result from an increase in downstream pressure, a reduction in the potable water supply pressure, or a combination of both. Increases in downstream pressure can be created by pumps, temperature increases in boilers, etc. Reductions in potable water supply pressure occur whenever the amount of water being used exceeds the amount of water being supplied, such as during water line flushing, fire fighting, or breaks in water mains.

ANSWER: A cross-connection is any temporary or permanent connection between a public water system or consumer's potable (i.e., drinking) water system and any source or system containing nonpotable water or other substances. An example is the piping between a public water system or consumer's potable water system and an auxiliary water system, cooling system, or irrigation system.

ANSWER: Backsiphonage is backflow caused by a negative pressure (i.e., a vacuum ~ or partial vacuum) in a Public water system or consumer's potable water system. The effect is similar to drinking water through a straw. Backsiphonage can occur when there is a stoppage of water supply due to nearby fire fighting, a break in a water main, etc.

ANSWER: An air gap is a vertical, physical separation between the end of a water supply outlet and the flood-level rim of a receiving vessel. This separation must be at least twice the diameter of the water supply outlet and never less than one inch. An air gap is considered the maximum protection available against backpressure backflow or backsiphonage but is not always practical and can easily be bypassed.


ANSWER: An RP is a mechanical backflow preventer that consists of two independently acting, spring-loaded check valves with a hydraulically operating, mechanically independent, spring-loaded pressure differential relief valve between the check valves and below the first check valve. It includes shutoff valves at each end of the assembly and is equipped with test cocks. An RP is effective against backpressure backflow and backsiphonage and may be used to isolate health or nonhealth hazards.


ANSWER: A PVB is a mechanical backflow preventer that consists of an independently acting, spring-loaded check valve and an independently acting, spring-loaded, air inlet valve on the discharge side of the check valve. It includes shutoff valves at each end of the assembly and is eqipped with test cocks. The PVB may be used to isolate health or nonhealth hazards but is effective against backsiphonage only.


ANSWER: A DC is a mechanical backflow preventer that consists of two independently acting, spring-loaded check valves. It includes shutoff valves at each end of the assembly and is equipped with test cocks. A DC is effective against backpressure backflow and backsiphonage but should be used to isolate only non-health hazards.


ANSWER: The RDC is similar to a DC in that it is a mechanical backflow preventer consisting of two independently acting, spring-loaded check valves. However, it usually does not include shutoff valves, mar or may not be equipped with test cocks or ports, and is generally less reliable than a DC. The RDC is effective against backpressure backflow and backsiphonage but should be used to isolate only non-health hazards and is intended for use only in water service connections to single-family homes.

FAQ Fire Water

ANSWER: A hand held fire extinguisher using water for the extinguishing agent which is expelled by compressed air. Wetting agents may be added to the water and AFFF foam can be used in similar extinguishers.

ANSWER: An alarm device that signals that a firefighter is in trouble. It can be activated manually by the firefighter, or activates automatically if the firefighter stops moving. May be integral to SCBA or separately activated. Also known as a PASS device (personal alert safety system) or PDA (personal distress alarm).

ANSWER: (pronounced "A-Triple-F", also called "Class B"): bubbles that act as surfactant to coat and penetrate ordinary fuels (e.g., wood, paper) to prevent them from burning at normal temperatures; also used on "Class B" (oil/gasoline) fires to spread a non-volatile film over the surface of the fuel. Applied using eductor or compressed air foam system (CAFS) and pumped through fire hose to a foam nozzle (or sometimes a less-effective fog nozzle).

ANSWER: Small-diameter fire hose (3/4–1 inch), often carried on booster reel, preconnected to pump of an engine (and the booster tank) for putting out small fires near the truck without having to connect to a fire hydrant; easily recovered with a motorized reel. Also known as "red line" for the common red rubberized outer layer. Booster hose is also used for high pressure fog (HPF) applications.

ANSWER: Large tank designed to be transported to an incident and left; larger than a tote tank.

ANSWER: A type of coupling used by the CFA, it is used mainly on the Australian 64 mm hose, it provides a very secure coupling, obviously the threading of the coupling is repeated 3 times, it is non-hermaphrodite.

ANSWER: A check valve, clack valve, non-return valve or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction.

ANSWER: Underground water storage tank that is intended for firefighting use in areas with inadequate water supply.

ANSWER: Pike pole under 5 ft long

ANSWER: Narrow, collapsible ladder used to access an attic space via a scuttle hole, which are often found in closets and other narrow passages. Also known as a closet ladder, folding ladder or "pencil ladder." Required to be carried on pumpers by NFPA 1901.

ANSWER: Portion of fire hydrant or sprinkler system connecting main loops to smaller loops where outlets are located.

ANSWER: A valve isolating a segment of a (usually underground) piping system. This may be useful for dealing with impairments or maintenance.

ANSWER: Fire hose adapter for connecting two "male" couplings together; may also adapt different sizes on either side.

ANSWER: Hose coupling adapter with two male-threaded connectors back-to-back; used for connecting two female couplings together.

ANSWER: A fire extinguishing agent. It works by breaking the chemical chain reaction in the "fire tetrahedron".

ANSWER: A fire hydrant with a valve located at the bottom of the barrel, near the water main. The barrel of the hydrant remains dry until used. The prevents the hydrant from freezing in sub-zero temperatures. A dry hydrant is also an unpressurized pipe that can be used to draft (or draw) water from a pond or lake.

ANSWER: Fire extinguishing agents for use on flammable metals. Each agent is typically designed for use on either a single metal or very similar metals.

ANSWER: A sprinkler system having pressurized air (rather than water) in the distribution pipes until a heat-activated sprinkler head opens and releases the stored air pressure, which in turn opens the main water valve (and possibly an accelerator valve) to flow water to the open sprinkler(s); used where the protected premises are not heated during freezing temperatures.

ANSWER: Venturi device through which water flows under 200 psi pressure to create a partial vacuum in a tube attached at 90-degrees and open to the water stream passing overhead. The vacuum draws liquid foam concentrate from a reservoir, which mixes with the water stream through a metering device on the discharge side of the eductor where a firefighting hose is connected. Typically the 200 psi inlet water pressure is reduced to 95 psi discharge pressure as a result of the narrowness of the venturi in the eductor device.

ANSWER: Pumps that use the venturi principle to pump water on a fire ground. Can be used for salvage by removing flood waters or supply water to a fire appliance from an open water source. Water in the appliance is used to supply a flow of water to the ejector pump, which uses high pressure nozzles to entrain an increased volume of water in the hose returning to the fire appliance.

ANSWER: Handheld fire suppression device designed to be thrown into needed area. Fit stands for Fire Interruption Technology. Effective against Class A, B, or C fires.

ANSWER: It is a fluoroprotein film forming foam.

ANSWER: A fire stream characterized by small droplets of water. The droplets are unable to travel very far, but absorb heat very quickly because of the high surface area they present.

ANSWER: Backflow preventer at inlet of suction hose used in drafting; helps avoid losing prime by keeping water from running back out of the suction hose.

ANSWER: brand of wind-up, fire alarm telegraph system for sending coded pulses to alert central alarm station of fire alarm activation; often still found in red boxes on street corners.

ANSWER: Control valve with a solid plate operated by a handle and screw mechanism. Rotating the handle moves the plate into or out of the waterway.

ANSWER: Water storage tank for fire protection; arranged above protected area to provide flow of water by gravity when needed.

ANSWER: A suppression technique consisting of finely atomized water droplets at several hundred pounds per square inch of pressure. By far, one of the most efficient suppression techniques available. Advantages include a *very* high conversion rate, unmatched atmospheric cooling and control of thermal layers, very little wasted water (and consequent water damage), and the ease of managing a small diameter booster line (defined above) during application. Disadvantages are lack of distance, lack of penetration into various materials, and high risk of burns to the attack crew. HPF is quite popular in Europe, but was discarded in the U.S. due to different building construction and the resulting increase in disadvantages.

ANSWER: National Pipe Straight Hose thread, also known as IPT (Iron Pipe Thread, or International Pipe Thread). Like NH threads, NPSH threads are commonly used in fire hose couplings, but the two types are not interchangeable with each other and cannot be connected together without adapters. NPSH threads have a slightly smaller diameter and more threads per inch than NH, but NPSH hoses can be fitted to NPT (National Pipe Tapered) plumbing fixtures, as the diameters and thread pitches are similar.

ANSWER: Type of gate valve actuator arranged such that the valve stem moves in and out of the handle, thus externally indicating whether the valve is open or shut, unlike the more common gate valve wherein the stem rotates and only the gate moves up and down inside the fixture.

ANSWER: Ventilation of an area by the use of a fan to push clean air into that space and controlled use of openings for the escape of smoke and gasses.

ANSWER: A type of valve used for underground piping, having a lockable actuator atop a post with a window indicating "open" or "shut" status of the valve. It can be used to control a sprinkler system, hydrant or other device, or may be used as a divisional valve. Post indicator valves are also used for process and domestic water systems, and when this occurs on the same property, they are distinguished by color - red for fire, blue green or yellow for process water.

ANSWER: 1. (US) A system of pipes inside a building for conducting water for fire hose attachments; may be pressurized with water ("wet") or remain "dry" until activated in an emergency; supplied either from a fire hydrant attachment or from a fire engine's pump. Permits firefighters to reach higher levels of tall buildings without having to run hoses up the stairs. Known as "wet riser" and "dry riser" respectively in the United Kingdom.

2. (UK) A J- or T-shaped metal pipe used to access underground fire hydrants.

ANSWER: A popular brand of adjustable fog stream combination nozzle, now a ubiquitous term for that type of nozzle.

ANSWER: Hose appliance used for splitting one line into two discharges. Often a gated wye is used to allow and disallow water flow through the two separate discharges. Not to be confused with Siamese, which is used to bring two smaller lines together into one.

ANSWER: Large hose appliance for connecting supplemental pumps into long supply lines, in the form of a "Z"; may be improvised from two gated wye valves and a double female between two of the gated outlets or from a siamese that has one inlet connected to one outlet of a gated wye.

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