Firefighting Basics: Pressurized Water Supply

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Questions and Answers

What is the minimum residual pressure that must be maintained during pumping operations?

10 kPa

20 kPa (correct)

50 kPa

30 kPa

Why is selecting a hydrant not solely based on proximity to the fire?

Proximity may indicate inadequate water supply from smaller mains. (correct)

Closer hydrants always have higher water flow rates.

All nearby hydrants are interconnected.

Safety protocols prioritize distance over water capacity.

What is a characteristic of hydrants located on dead-end mains?

They are the preferred choice for emergency supply.

They often have lower amounts of sedimentation.

They can supply water from multiple directions.

They generally have higher amounts of sediment and deterioration. (correct)

What must be done to a hydrant before connecting the intake hose?

It should be briefly opened and flushed. Signup and view all the answers

What is the main consequence of overtaking a water system during fire operations?

Damage to piping and reduced water flow. Signup and view all the answers

How can fire departments ensure effective use of their water supply system?

By collaborating with local water supply officials. Signup and view all the answers

What happens if the residual pressure in the mains drops too low?

Contamination from external sources may occur. Signup and view all the answers

What is an important factor when making a hydrant connection?

The connection should be made with minimal delay. Signup and view all the answers

What is a primary risk when making a forward lay over long distances?

Insufficient supply hose carried on the pumper Signup and view all the answers

What can help to manage the flow of water while making a forward lay?

Using a four-way hydrant valve Signup and view all the answers

Which scenario would require a second pumper during the forward lay?

Long distance with inadequate hose length Signup and view all the answers

What is one operational procedure after laying the hose?

Connect to the hydrant immediately Signup and view all the answers

What is the typical diameter of the second discharge on a four-way hydrant valve?

4½ or 5 inches Signup and view all the answers

Why might a pumper need to be placed at the hydrant?

To maximize the available pressure Signup and view all the answers

What might happen if a water supply pumper runs out of hose?

Relay pumping may be needed Signup and view all the answers

Which of the following statements is NOT true regarding the procedures after making a forward lay?

Jurisdictions have consistent procedures across the board Signup and view all the answers

What is the primary function of the clapper valve during the operation of a forward lay?

To prevent backflow into the hydrant once the pressure is adequate. Signup and view all the answers

During the operation of a four-way valve, what should be done first after connecting it to the hydrant?

Open the hydrant. Signup and view all the answers

What critical action occurs when the pressure in the pump builds during a forward lay?

The clapper valve closes, redirecting flow from the hydrant to the pump. Signup and view all the answers

What is the purpose of attaching gate valves to unused hydrant discharges on dry barrel hydrants?

To allow for future connections without disrupting the existing flow. Signup and view all the answers

Which of the following is true regarding the original supply line after the pressure in the pumper builds?

It begins to be fed by the water from the pump instead of the hydrant. Signup and view all the answers

Which step is necessary to ensure that the second pumper can be connected without affecting the initial supply line?

Open the four-way valve on the hydrant after connecting it. Signup and view all the answers

What can happen if the discharge flow volume from the fire pump is increased excessively?

Damage may occur to the pump or water supply system. Signup and view all the answers

Why is it dangerous to pump at a low residual pressure below 20 psi?

It may lead to cavitation of the pump and hose collapse. Signup and view all the answers

Which statement accurately describes the relationship between friction loss and incoming pressure?

As discharge volume increases, the incoming pressure may decrease due to friction loss. Signup and view all the answers

When connecting a supply line, which statement should the driver/operator keep in mind?

Intake pressure should be consistently monitored to avoid pump damage. Signup and view all the answers

What results from improperly managing the supply hose during operation?

It may create a vacuum and reduce pressure. Signup and view all the answers

What is a critical aspect of a reverse lay when using medium diameter hose?

The distance must be minimized to reduce friction loss. Signup and view all the answers

Under what circumstance is water supply established for reverse lays?

When an increase in hydrant pressure is required. Signup and view all the answers

Which hose size is designated as medium diameter hose (MDH)?

2 1/2-inch (65 mm) or 3-inch (77 mm) Signup and view all the answers

What component is essential when conducting a reverse lay with threaded couplings?

Double male adapters at the hydrant. Signup and view all the answers

What is the main role of the water supply pumper in a two-pumper operation?

To supply water to the attack pumper. Signup and view all the answers

Why might a four-way hydrant valve be utilized during a reverse lay?

To facilitate changing from pump pressure to hydrant pressure. Signup and view all the answers

What should be done after connections to the hydrant are made, before opening it?

Conduct several checks, including closing the tank-to-pump valve. Signup and view all the answers

Which operation allows the second pumper to be free from the scene when water demand diminishes?

Employing a four-way hydrant valve. Signup and view all the answers

What does a check valve in a tank-to-pump line do?

Prevents water entry into the tank under pressure. Signup and view all the answers

How should the hose be loaded for a reverse lay with threaded couplings?

With the male coupling coming out first. Signup and view all the answers

What is one method to prevent pump overheating during intermittent use of water?

Establish a continuous minimum flow of water. Signup and view all the answers

Which of the following actions can help manage water discharge without interfering with fireground operations?

Open the valve for the booster reel and direct water away from the operation. Signup and view all the answers

During prolonged pumping operations, which method may not sufficiently cool the pump?

Using a bypass circulator. Signup and view all the answers

What should be done if a tank-fill valve becomes blocked?

Partially open the tank-fill valve to relieve pressure. Signup and view all the answers

When determining additional water available from a hydrant, which method is NOT commonly used?

Linear Regression Method. Signup and view all the answers

What issue can arise if water enters the tank of a pump built before 1991 under pressure?

Damage to the tank may occur due to inadequate venting. Signup and view all the answers

In a reverse lay operation, what is acceptable if the intake includes a shutoff valve?

To bleed off air while also pumping in water from the tank. Signup and view all the answers

What should a driver/operator do after transitioning to an external water supply?

Close the tank-to-pump valve. Signup and view all the answers

What is a potential feature missing in pumps manufactured before 1991?

A tank-to-pump shutoff valve. Signup and view all the answers

Why is it essential to bleed off air from the intake line?

To prevent air locks that can disrupt water flow. Signup and view all the answers

What should the driver/operator do if the hydrant is inoperable?

Disengage the pump drive system before relocating the apparatus. Signup and view all the answers

What is the consequence of running a pump without water for an extended period?

It may lead to overheating and faster wear of components. Signup and view all the answers

In what position should the transfer valve be set when operating a two-stage pump to increase discharge pressure?

Series (pressure) position. Signup and view all the answers

What should the driver/operator do if the master intake gauge drops below 20 psi (140 kPa)?

Reduce the throttle and monitor the situation. Signup and view all the answers

What is typically required when supplying large amounts of water using a relay operation or master stream?

Set the transfer valve to a parallel (volume) setting. Signup and view all the answers

Why is it important to open all valves slowly, especially with large diameter hoses?

To prevent pressure surges that could damage hoses. Signup and view all the answers

When should the relief valve or governor be set?

After reaching the required pressure and flow. Signup and view all the answers

What could happen if the pressure is increased when the master intake gauge is already at 20 psi (140 kPa)?

It may cause cavitation in the pump. Signup and view all the answers

Study Notes

Pressurized Water Supply Sources

Primary sources include fire hydrants and supply hoses from other pumpers.
Water enters the pump under pressure; friction loss can decrease this incoming pressure.
Excessive discharge volume can risk damaging the pump or water supply system.
Low residual pressure (below 20 psi or 140 kPa) can collapse supply hoses or cause cavitation.

Cavitation Risks

Maintain at least 20 kPa residual pressure on the master intake gauge during operations.
Water supply systems must also maintain this minimum pressure to prevent contamination and sediment damage.
A cooperative relationship with local water supply officials is essential for optimal water system use.

Hydrant Operations

Hydrant usage involves both direct supply lines and relay operations.
Proximity of hydrants may not ensure adequate supply; closer hydrants can pose safety hazards.
Knowledge of the water supply system is crucial for effective hydrant selection.

Types of Mains

Dead end mains allow water flow in one direction and may have higher sedimentation and deterioration.

Making Hydrant Connections

Flush hydrants briefly to clear debris before connecting hoses.
Quick and efficient connections are critical for operational effectiveness.

Forward Lay Method

A forward lay involves laying hoses from the hydrant to the fire location.
Distance and flow demand may necessitate positioning a pumper at the hydrant for pressure support.
Four-way hydrant valves can facilitate simultaneous connections and maintain water flow continuity during pump transitions.

Reverse Lay Method

Hose is laid from the fire scene back to the water source, useful for initial size-up by the driver/operator.
This method can ensure the water supply remains established even if apparatus remain at the source.
Load hose with appropriate couplings based on connection needs when executing a reverse lay.

Getting Water into the Pump

Conduct checks on valves before opening hydrants to safeguard against pressure issues.
Newer pumps often have check valves to prevent unwanted water intake.

Hose and Pumper Types

Medium Diameter Hose (MDH) is essential for relay-supply and attack operations.
Attack pumpers supply fire scenes directly, while water supply pumpers transport water to attack lines.

Two-Pumper Operations

An attack pumper initiates operations using onboard water; a water supply pumper lays a supply line back to the water source.

Pump Operation Guidelines

Avoid running pumps without water, as this can cause overheating and damage.
Engage pumps promptly as water should be expected within minutes of connection.
Adjust the transfer valve according to water demand; series for pressure and parallel for volume.

Safety and Efficiency Measures

Maintain a minimum flow to prevent pump overheating during operations.
Use booster lines for quick discharges to keep pump flow continuous.
Slow valve openings are essential for filling hoses before pressure establishment.

Monitoring and Adjustments

Monitor master intake and discharge gauges during operations.
If master intake pressure drops below 20 psi (140 kPa), do not increase throttle to avoid cavitation.
Set relief valves and governor accordingly once required pressure and flow rates are achieved.

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Description

Test your knowledge on the operation of pressurized water supply sources in firefighting, focusing on hydrants and supply hoses. Understand the dynamics of pressure and flow, including the effects of friction loss in water systems. This quiz will help reinforce essential concepts for driver/operators.