Editing Fire hydrant (section)

==Operation==
The user (most likely a [[fire department]]) attaches a [[Fire hose|hose]] to the fire hydrant, then opens a [[valve]] on the hydrant to provide a powerful flow of water, on the order of {{convert|350|kPa|psi|lk=on}}; this [[pressure]] varies according to region and depends on various factors (including the size and location of the attached [[water main]]). This user can attach this hose to a [[fire apparatus|fire engine]], which can use a powerful [[pump]] to boost the [[water pressure]] and possibly split it into multiple streams. One may connect the hose with a [[threaded pipe|threaded]] connection, instantaneous "[[quick connector]]" or a [[Storz connector]].<ref>{{Cite news |last=Wesser |first=James |date=February 25, 2024 |title=How do fire hydrants work? |url=https://www.abc27.com/digital-originals/how-do-fire-hydrants-work/ |work=[[WHTM]]}}</ref>

If a fire hydrant is opened or closed too quickly, a [[water hammer]] can occur and damage nearby pipes and equipment. The water inside a charged [[Hoseline|hose line]] causes it to be very heavy, and high-water pressure causes it to be stiff and unable to make a tight turn while pressurized. When a fire hydrant is unobstructed, this is not a problem, as there is enough room to adequately position the hose.{{Clarification needed|reason=Is this sentence still about the case when the hydrant is opened or closed too quickly? Or is it a separate thought from the beginning of the paragraph?|date=January 2025}}

Most fire hydrant valves are not designed to [[throttle]] the water flow; they are designed to be operated full-on or full-off. The valving arrangement of most dry-barrel hydrants is for the drain valve to be open at anything other than full operation. Usage at partial opening can consequently result in considerable flow directly into the soil surrounding the hydrant, which, over time, can cause severe [[Hydrodynamic scour|scouring]]. [[Gate valve|Gate]] or [[Butterfly valve|butterfly valves]] can be installed directly onto the hydrant opening to control individual outputs and allow for changing equipment connections without turning off the flow to other outlets. These valves can be up to {{convert|12|in|cm}} in diameter to accommodate the large central "steamer" outlets on many US hydrants. It is good practice to install valves on all outlets before using a hydrant as the protective caps are unreliable and can cause major injury if they fail.

New [[firefighter]]s are often trained extensively on fire hydrants in the fire academy to be quick and safe while connecting the fire engine to the fire hydrant (usually within one minute). Time is often critical as other firefighters will be waiting for the water supply. When operating a hydrant, a firefighter typically wears appropriate [[personal protective equipment]], such as [[glove]]s and a [[helmet]] with [[face shield]] worn. High-pressure water coursing through a potentially aging and [[Corrosion|corroding]] hydrant could cause a failure, injuring the firefighter operating the hydrant or bystanders.

In most jurisdictions it is illegal to park a car within a certain distance of a fire hydrant. In [[North America]], the distances are commonly {{convert|3|to|5|m|ft|0}}, often indicated by yellow or red paint on the curb. The rationale behind these laws is that hydrants need to be visible and accessible in an emergency. In the event that a car is illegally parked next to a fire hydrant when firefighters need access to it, firefighters are legally allowed to break the car's windows to run the hose through it, while the car owner receives a parking citation.

<gallery mode="packed">
File:Clappered.JPG|Clapper valve
File:Hydrant to truck.jpg|A [[New York City]] hydrant hooked to an [[Fire Department of New York|FDNY]] [[fire engine]] with a [[fire hose]] actively pumping water
</gallery>

=== Other uses===

====Street pooling====
[[File:Philadelphia fire hydrant.jpg|thumb|upright|Children playing in the spray of a fire hydrant in [[Philadelphia]] (1996)]]
In 1896, during a terrible [[heatwave]] in [[New York City]], the Commissioner of [[Public Works]] ordered the opening of the fire hydrants to provide relief to the population.<ref>Marc Bettinelli [https://www.lemonde.fr/societe/video/2017/06/26/street-pooling-d-ou-vient-cette-idee-d-ouvrir-des-bouches-a-incendie-en-periode-de-canicule_5151375_3224.html « Street pooling » : d'où vient cette idée d'ouvrir des bouches à incendie en période de canicule ?] Le Monde, 26 June 2017</ref> Today some US communities provide low flow [[irrigation sprinkler|sprinkler]] heads to enable residents to use the hydrants to cool off during hot weather, while gaining some control on water usage. Sometimes those simply seeking to play in the water remove the caps and open the valve, providing residents a place to play and cool off in summer.

====Preventing misuse====
To prevent casual use or misuse, the hydrant requires special tools to be opened, usually a large wrench with a [[Pentagon|pentagonal]] socket. [[Vandalism|Vandals]] sometimes cause monetary loss by wasting water when they open hydrants. Such vandalism can also reduce municipal water pressure and impair firefighters' efforts to extinguish fires. Most fire hydrants in [[Australia]] are protected by a silver-coloured cover with a red top, secured to the ground with bolts to protect the hydrant from vandalism and unauthorized use. The cover must be removed before use.

In most areas of the [[United States]], [[General contractor|contractors]] who need temporary water may purchase permits to use hydrants. The permit will generally require a [[Water meter|hydrant meter]], a [[gate valve]] and sometimes a [[Check valve|clapper valve]] (if not designed into the hydrant already) to prevent [[backflow]] into the hydrant. Additionally, residents who wish to use the hydrant to fill their in-ground [[swimming pool]] are commonly permitted to do so, provided they pay for the water and agree to allow firefighters to [[Draft (water)|draft]] from their pool in the case of an emergency.

[[Municipal services]], such as [[street sweeper]]s and tank trucks, may also be allowed to use hydrants to fill their water tanks. Often [[sanitary sewer|sewer]] maintenance trucks need water to flush out [[sewerage]] lines and fill their tanks on site from a hydrant. If necessary, the municipal workers will record the amount of water they used or use a meter.

Fire hydrants may be used to supply water to [[riot control]] vehicles. These vehicles use a high-pressure [[water cannon]] to discourage rioting.

Since fire hydrants are one of the most accessible parts of a [[water distribution system]], they are often used for attaching pressure gauges or loggers or monitor system water pressure. Automatic flushing devices are often attached to hydrants to maintain chlorination levels in areas of low usage. Hydrants are also used as an easy above-ground access point by leak detection devices to locate leaks from the sound they make.