Hydrants
There are two different kinds of fire hydrants, "wet" and "dry". The designation refers to whether the hydrant is full of water when not in use.
Dry hydrants are usually used in areas where there is a risk of freezing. To keep the hydrant from being damaged or clogged by ice, the hydrant's valve is set down in the ground well below the frost line. This type of hydrant is recognizable by it's single nut on it's top, which is attached to a shaft going down the inside of the hydrant to below it's base. One disadvantage to this type of hydrant is that because there is only one controlling valve, once water is flowing no additional hoses can be connected to the hydrant without first turning off the water. An advantage that dry hydrants have is that if they are hit or sheared off by a vehicle, they are less likely to gush water, because their valve is somewhat protected below the ground.
Wet hydrants are always full of water, so each outlet has it's own valve. These hydrants are recognizable by the valve nut on the opposite side of the hydrant from each outlet. These hydrants allow individual flow control for each outlet, but are vulnerable to freezing because they are always full of water.
Left: a 3-outlet wet hydrant. Center: a 3-outlet dry hydrant. Right: a traditional style round-topped 3-outlet dry hydrant.
Both wet and dry hydrants are used in this department's response area. Hydrants have a variety of outlet sizes and styles, depending on how old they are and who installed them. Because of this, all trucks and engines in the department carry a variety of adapters so that they can connect their supply lines to any hydrant outlet.
All hydrants valve nuts are five-sided (top photo) to prevent tampering or unauthorized use. Fire departments carry special hydrant wrenches to allow them to operate hydrants. When connecting a hose to a hydrant, a firefighter will carry a kit containing the special hydrant wrench and rubber mallet (bottom left), and spanner wrenches (bottom right), to help loosen stuck outlet caps and tighten hose couplings.
Wrenches are kept in a number of locations on the engines, so as to be readily accessable when needed. In this photo, the wrenches are conveniently stored on the front bumper of engine 13, next to a short supply line that gets hooked up to the hydrant.
Hydrants are also referred to as "Fire Plugs". This goes back to colonial times, when water mains were made out of hollowed logs. When a fire was discovered, the firefighters would dig down into the ground to expose the pipe, and bore a hole in it to get to the water. When they were done, they would put a plug into the pipe to seal it up. Next time, this plug would allow quicker access to the water. When hydrants were installed, the name stuck.
For more information on all aspects of hydrants, visit firehydrant.org.
This now-famous photo is one of a large series taken by fire photographer Danny Barlogio at a multi-alarm fire in Oakland, CA, and pretty much speaks for itself as to why one should not park in front of a fire hydrant. Photo 2000; used with permission.
Blue Dots
Blue Dots, also referred to as Botts' Dots, are placed near the center of roadways to help firefighters locate hydrants at night, in bad weather, or when the hydrant is difficult to locate because of brush or other obstructions. They are standarized to a blue color so that they will stand out from, and not be confused with the red, white, and amber dots which are all used for traffic lane marking.
The Blue Dot is a raised plastic retroflective block approximately 4" (10cm) square, which is glued to the pavement, usually near the center line on a roadway. It is shown here marking a dry hydrant.
The Blue Dots are checked annually during routine hydrant inspection and flushing, and if found to be missing or damaged are either replaced then or are noted for replacement at some later date. Members of the Volunteer Division often replace the Blue Dots.
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