UNIT 5. BACKFLOW PREVENTION -
TEST YOUR KNOWLEDGE
QUESTIONS AND ANSWERS
Define and briefly explain "backflow." - Correct Answers -The movement of a liquid in
reverse of the normal direction of flow in a piping system. Backflow can also occur in the
injection line, causing the pesticide tank to overflow. Backflow results from either
backsiphonage or backpressure.
Why is backflow prevention so important? - Correct Answers -To protect water sources
from pollution. Backflow prevention is a vital part of safe and effective chemigation.
Define "backsiphonage" and name some common causes. - Correct Answers -A
vacuum caused by reduced pressure in a supply line to a piping system. This vacuum
causes a siphoning action. Common causes are:
1. High liquid velocity in pipelines.
2. A line break or repair that is lower than a service point.
3. Lowered main pressure due to a high rate of water withdrawal (ex. fire fighting).
4. Reduced supply pressure on the suction side of the booster pump.
Define "backpressure" and name some common causes. - Correct Answers -A
difference in pressure when a supply line is connected to a high-pressure system. If the
system exceeds the operating pressure of the supply pipes, backpressure can result.
Common causes are:
1. Booster pumps.
2. Connections to boilers.
, 3. Cross connections with another system running at a higher pressure.
4. Elevated piping.
Define and briefly explain "cross connection." - Correct Answers -Any physical
connection between a public water system and any source of nonpotable liquid, solid, or
gas. The connection can be actual or potential. If this connection could contaminate the
public water supply by backflow, it is a cross connection.
What safety equipment must you have if your chemigation system draws from a
domestic or municipal water supply? - Correct Answers -A reduced pressure-principle
backflow preventer or a two-pump system with an air gap.
How can you find out what safety equipment is required for chemigation of a pesticide?
- Correct Answers -Consult the label. Under federal law, pesticide labels must state
which safety equipment is required for chemigation of the product.
Under the Label Improvement Program (LIP), what safety devices must you have on
your irrigation pipeline? - Correct Answers -1. A check valve.
2. A vacuum relief valve.
3. An automatic low-pressure drain.
Under the LIP, what safety devices must you have on your injection pipeline? - Correct
Answers -1. An automatic, quick-closing check valve.
2. A normally closed solenoid valve.
3. Interlocking, automatic shutoff controls.
4. A pressure switch.
5. A metering-type injection pump or device.
Where should you install safety devices on your irrigation system? - Correct Answers -1.
Between the irrigation pump discharge and the point of pesticide injection.
TEST YOUR KNOWLEDGE
QUESTIONS AND ANSWERS
Define and briefly explain "backflow." - Correct Answers -The movement of a liquid in
reverse of the normal direction of flow in a piping system. Backflow can also occur in the
injection line, causing the pesticide tank to overflow. Backflow results from either
backsiphonage or backpressure.
Why is backflow prevention so important? - Correct Answers -To protect water sources
from pollution. Backflow prevention is a vital part of safe and effective chemigation.
Define "backsiphonage" and name some common causes. - Correct Answers -A
vacuum caused by reduced pressure in a supply line to a piping system. This vacuum
causes a siphoning action. Common causes are:
1. High liquid velocity in pipelines.
2. A line break or repair that is lower than a service point.
3. Lowered main pressure due to a high rate of water withdrawal (ex. fire fighting).
4. Reduced supply pressure on the suction side of the booster pump.
Define "backpressure" and name some common causes. - Correct Answers -A
difference in pressure when a supply line is connected to a high-pressure system. If the
system exceeds the operating pressure of the supply pipes, backpressure can result.
Common causes are:
1. Booster pumps.
2. Connections to boilers.
, 3. Cross connections with another system running at a higher pressure.
4. Elevated piping.
Define and briefly explain "cross connection." - Correct Answers -Any physical
connection between a public water system and any source of nonpotable liquid, solid, or
gas. The connection can be actual or potential. If this connection could contaminate the
public water supply by backflow, it is a cross connection.
What safety equipment must you have if your chemigation system draws from a
domestic or municipal water supply? - Correct Answers -A reduced pressure-principle
backflow preventer or a two-pump system with an air gap.
How can you find out what safety equipment is required for chemigation of a pesticide?
- Correct Answers -Consult the label. Under federal law, pesticide labels must state
which safety equipment is required for chemigation of the product.
Under the Label Improvement Program (LIP), what safety devices must you have on
your irrigation pipeline? - Correct Answers -1. A check valve.
2. A vacuum relief valve.
3. An automatic low-pressure drain.
Under the LIP, what safety devices must you have on your injection pipeline? - Correct
Answers -1. An automatic, quick-closing check valve.
2. A normally closed solenoid valve.
3. Interlocking, automatic shutoff controls.
4. A pressure switch.
5. A metering-type injection pump or device.
Where should you install safety devices on your irrigation system? - Correct Answers -1.
Between the irrigation pump discharge and the point of pesticide injection.
