Water Supplies Flashcards
Describe Static supply
These are bodies of water such as dams, rivers, lakes, and swimming pools that are accessed by ‘draughting’. Static supplies are sometimes referred to as ‘open water’.
Describe Reticulated supply
This refers to water within a network of pipes ( mains ) which is accessed via various types of hydrants. reticulated water is sometimes referred to as ‘closed water’.
3 types of mains
Trunk mains
Service mains
Ring mains
Describe trunk mains
Trunk mains vary in size from 600mm to 3000mm. These mains deliver water from the source to the treatment plants and then on to the service reservoirs.
Describe service mains
Service mains form a network of pipes that feed the various pressure zones from the reservoir. They are laid underground and consumers draw water from them by means of smaller water pipes tapped in. Usually between roadway and footpath. In residential areas usually 100mm, in business and industrial areas between 150mm and 600mm.
What does a shut-off valve do
Allow sections of the main to be isolated in case of breakage or repair. They can also be shut off in order to allow greater pressure and flow for ACTF&R units.
Describe pressure
Is the force at which water is delivered from the mains. Pressure is what pushes the water ( fluid ) through the lines and equipment. Usually measure in kPa ( kilopascals )
What affects pressure
The length of main between the pump, or other elevated pressure source such as reservoir, and the hydrant. Weather or not there are pumping stations/ boosters in the system. The number and size of hoses or appliances attached to the main. The quantity of water being used by other consumers.
Describe flow
Is the quantity of water being delivered in a given time. the volume of water ( fluid ), that flows through a passage 9 hose line ) of any given section during a unit of time. i.e litres per minute.
What affects flow
The diameter of the main. The condition of the internal surface of the main. Older mains may suffer from internal corrosion or tuberculation ( formation of mineral deposits ) which will affect the smoothness. The pressure at which the main is working.
Describe spring valve hydrants
Commonly referred to as ‘ball valve’ hydrants. Has a mushroom shaped valve, which is held onto the sealing washer by the pressure of a non-ferrous spring. Accessed via a standpipe.
3 mains types of hydrants
Spring valve hydrants High capacity hydrants Pillar hydrants
Describe high capacity hydrants
Supplies large volumes of water. Usually located in high risk areas such as hospitals, shopping centres, industrial areas, high density housing, schools and multi-storey buildings. Have 2 65mm storz couplings and 1 125mm storz coupling covered by blank caps, accessed by high capacity hydrant key. They are cast iron approx 800mm high and 400mm wide painted yellow for easy visibility. In some areas Icon water has replaced with a grouping of spring valves.
Describe pillar hydrants
Not normally installed anymore. Same are in use some are heritage listed with a spring valve at the base. The shut-off valve is fitted with a spindle on top of the riser that is opened by use of ‘pillar hydrant key’ or the fitted hand wheel.
Describe a stand pipe
A standpipe is a FF’s means of accessing spring valve hydrants. It has 2 65mm storz couplings and is capable of twin or single outlet flow by the use of the shut off handle. The lugs of the standpipe fit into the bayonet lugs of the spring valve and when screwed tightly puts pressure on the seal at the base. the hand wheel can then be rotated clockwise to extend a rod down the barrel, the rod then forces the valve off its seat to supply water.
What is water hammer
If water flow is suddenly cut off, its kinetic energy is converted into pressure energy that must be absorbed by the pipe and fittings. This shock, and the pressure waves that it generates, is transmitted through the column of water and gives rise to what is known as water hammer. Water hammer can be so great as to rupture hose joints, hydrants, water mains or pump casing.
How to avoid water hammer
Shut off branches smoothly and steadily. Close hydrants smoothly and steadily. Shut off deliveries and collectors at the pump smoothly and steadily. If vehicles must be driven over charged line of hose, ensure that it is done very slowly. And use ramps where available.
How is a hydrant indicated
By a ‘FH’ embossed metal plate affixed to the gutter. On the road adjacent is a blue ‘cats-eye’ usually located next to the centre line on the side that the hydrant is located. A small arrow may also be printed on the ‘cats-eye’ pointing to the hydrant.
Hydrant positioning
60-90m intervals in residential areas. Larger shopping centres or industrial areas will have a high capacity hydrant every 135m with spring valve hydrants interspersed every 45m. On roads with mains where only vehicle fires are apparent every 180m.
What ways can hydrant booster systems be configured
Internal hydrant booster system
Attack hydrant booster system
Sprinkler booster system
Combined sprinkler and hydrant booster system
Where would you find hydrant booster systems
As a general rule on thumb, any building of two or more levels ( above or below ground) must have a internal hydrant system.
Where would you find internal hydrants pre 1994
Will be located no more than 4m from any designated exit.
Where would you find internal hydrants post 1994
Inside a fire-isolated stairwell.
What’s inside a booster cabinet
Connection points which allow FF’s to connect to internal hydrant system to boost pressure. Some systems have their own pumps. Usually twin 65mm storz with a pressure gauge above stating operating pressure. Access to mains supply is next to boost-able storz couplings or close by. Block plan. Sign with maximum test and operating pressures.
Describe attack hydrants
Internal and external attack hydrants can be seen as a network of ‘pre-laid’ hose to assist in the ease and speed of firefighting operations.
How much coverage must attack hydrants have
Internal attack hydrants must cover all internal areas with a 10m hose stream from a 30m hose. External attack hydrants must provide coverage to all portions of the building with a 10m stream from a 60m hose and a minimum of 1m of hose access into any room served by the installation.
Describe ring mains
In areas of high fire rish such as fuel depots, water mains are run completely around the risk then coupled back into the water supply.
Because water flows both ways possible flow is increased. If one side is damaged the loop will still allow flow through the other side.
