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ASSE 6020 practice questions

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Question 1Cross-Connection Control Program Administration

Which document typically serves as the legal foundation authorizing a community water system to operate a cross-connection control program?

  1. The utility's published annual consumer confidence report
  2. The utility's employee safety handbook
  3. The state primacy agency's cross-connection rules and the utility's ordinance Correct answer.
  4. The manufacturer's installation manual for backflow assemblies

Explanation

A cross-connection control program draws its authority from state drinking water regulations adopted under the Safe Drinking Water Act and from the local ordinance or rule enacted by the water supplier. The ordinance gives the utility power to require containment assemblies and to enforce compliance.

Question 2Cross-Connection Control Program Administration

A newly hired cross-connection control specialist is being trained. Which task is generally reserved for a certified backflow prevention assembly tester rather than the program administrator?

  1. Issuing a notice of noncompliance to a customer
  2. Performing the annual field test of a reduced pressure principle assembly Correct answer.
  3. Maintaining the inventory of containment assemblies
  4. Reviewing site plans for a new commercial building

Explanation

Field testing of backflow assemblies requires tester certification recognized by the state or an approved certifying body. Program administration tasks such as inventory, plan review, and enforcement are performed by program staff.

Question 3Cross-Connection Control Program Administration

Under a typical containment approach, where is the required backflow prevention assembly installed?

  1. At each individual fixture inside the building
  2. Inside the utility's main line upstream of the tap
  3. At the point where the customer's private plumbing connects to the public water main Correct answer.
  4. At the water treatment plant discharge only

Explanation

Containment protects the public distribution system by placing an assembly at the service connection or immediately downstream of the meter. Protection of individual fixtures is the separate concern of internal isolation.

Question 4Cross-Connection Control Program Administration

Which hazard classification applies to a cross connection that could introduce a substance causing illness or death if ingested?

  1. Non-health hazard
  2. Minor hazard
  3. Health hazard Correct answer.
  4. Aesthetic hazard

Explanation

A health hazard is any actual or potential connection that could introduce contamination capable of causing sickness or death. Non-health hazards affect only taste, odor, or appearance.

Question 5Cross-Connection Control Program Administration

A program administrator is choosing a device for a continuous-pressure, health-hazard application. Which assembly provides the highest level of protection?

  1. Atmospheric vacuum breaker
  2. Pressure vacuum breaker assembly
  3. Reduced pressure principle backflow prevention assembly Correct answer.
  4. Double check valve assembly

Explanation

The reduced pressure principle assembly is rated for health hazards and protects against both backpressure and backsiphonage because it includes a relief valve that discharges if differential pressure is lost.

Question 6Cross-Connection Control Program Administration

What is the primary purpose of maintaining a cross-connection control program inventory?

  1. To track which assemblies exist, their locations, and their test due dates Correct answer.
  2. To list customers eligible for rate discounts
  3. To document employee vacation schedules
  4. To record the utility's water production volumes

Explanation

An inventory is the backbone of program management because it records each assembly, its location, and its testing history so that compliance can be tracked and overdue tests identified.

Question 7Cross-Connection Control Program Administration

Which term describes a condition in which the pressure in the customer's piping exceeds the pressure in the public supply, potentially forcing contaminants into the main?

  1. Backsiphonage
  2. Water hammer
  3. Backpressure Correct answer.
  4. Cavitation

Explanation

Backpressure occurs when downstream pressure rises above supply pressure, such as from a booster pump or elevated tank. Backsiphonage instead results from a negative or reduced pressure in the supply itself.

Question 8Cross-Connection Control Program Administration

Which record should a program retain to demonstrate that an assembly was tested by an approved tester on a specific date?

  1. The customer's water bill
  2. The utility's capital improvement plan
  3. The completed test report form Correct answer.
  4. The building occupancy permit

Explanation

The test report documents the assembly identification, the test results, the tester's certification number, and the date. Retaining these reports supports enforcement and audit compliance.

Question 9Cross-Connection Control Program Administration

A commercial customer installs a booster pump downstream of the meter without notifying the utility. Which program response is most appropriate?

  1. Issue a boil-water notice to the entire system
  2. Ignore the pump because it is on private property
  3. Reduce the customer's meter size
  4. Require a containment assembly suitable for backpressure and verify installation Correct answer.

Explanation

A booster pump creates a backpressure condition that can reverse flow into the main. The program should require an approved assembly rated for backpressure at the containment point and confirm it is installed and tested.

Question 10Cross-Connection Control Program Administration

During a site survey of a car wash, the inspector finds a submerged make-up water line feeding a soap tank. What is the most significant concern?

  1. The soap tank may overflow onto the pavement
  2. The line may cause excessive water use
  3. The submerged inlet creates a backsiphonage hazard to the potable supply Correct answer.
  4. The line may reduce system pressure

Explanation

A submerged inlet in a tank of chemical solution is a classic health hazard because a drop in supply pressure can siphon the solution into the potable line. Air gaps or an approved assembly are needed to eliminate the connection.

Question 11Cross-Connection Control Program Administration

An irrigation system uses a pressure vacuum breaker assembly. The property owner later adds a chemical injection system upstream of the assembly. What is the correct program action?

  1. Require relocation of the injection point downstream of the assembly or upgrade to a reduced pressure principle assembly Correct answer.
  2. Remove the assembly entirely
  3. Require only that the injector be labeled
  4. Allow the installation because a vacuum breaker is present

Explanation

Chemical injection upstream of a pressure vacuum breaker places a health hazard on the supply side of a device that cannot protect against backpressure. The injection point must be downstream of the assembly, or protection must be upgraded to a reduced pressure principle assembly.

Question 12Cross-Connection Control Program Administration

A tester submits a report showing a reduced pressure principle assembly failed its differential pressure check. What should the program do first?

  1. Cancel the customer's water service permanently
  2. Accept the report and schedule the next annual test
  3. Require repair by a qualified technician and a passing retest Correct answer.
  4. Reclassify the assembly as a double check valve

Explanation

A failed test means the assembly is not providing adequate protection and must be repaired and retested. The program should track the repair until a passing report is received.

Question 13Cross-Connection Control Program Administration

A hospital wants to use a double check valve assembly on its fire sprinkler system, which contains antifreeze. How should the administrator evaluate this request?

  1. Approve it because double check valves are approved for all hazards
  2. Approve it because fire systems are exempt from containment
  3. Deny it because antifreeze is a health hazard requiring a reduced pressure principle assembly Correct answer.
  4. Require an atmospheric vacuum breaker at each sprinkler head

Explanation

Antifreeze in a fire protection system is a health hazard, so a device rated for health hazards is required. A double check valve assembly is approved only for non-health hazards.

Question 14Cross-Connection Control Program Administration

Which element is essential in a written cross-connection control ordinance to make enforcement effective?

  1. A description of the utility's organizational chart
  2. A schedule of employee performance reviews
  3. A list of approved pipe materials
  4. Authority to require installation, testing, and discontinuation of service for noncompliance Correct answer.

Explanation

Enforcement authority is what gives the ordinance practical effect, allowing the utility to mandate assemblies, require periodic testing, and terminate service if a customer refuses to comply.

Question 15Cross-Connection Control Program Administration

A utility wants to prioritize surveys. Which facility type should generally receive the earliest attention?

  1. A vacant commercial warehouse
  2. A single-family home with no irrigation
  3. A residential garage with a garden hose
  4. A mortuary with embalming operations Correct answer.

Explanation

Facilities handling toxic or infectious materials, such as mortuaries, present high health hazards and warrant priority in survey scheduling. Low-risk residential connections can follow.

Question 16Cross-Connection Control Program Administration

How should a program handle a customer who repeatedly fails to submit required annual test reports?

  1. Send a single reminder and take no further action
  2. Automatically waive the testing requirement
  3. Transfer responsibility to the neighboring property owner
  4. Apply escalating enforcement, including notices and possible service termination under the ordinance Correct answer.

Explanation

Consistent noncompliance should trigger a documented escalation process that follows the ordinance, up to and including discontinuation of service. Predictable enforcement sustains program credibility.

Question 17Cross-Connection Control Program Administration

A new backflow assembly is installed but the tester's report lists a serial number that does not match the assembly on site. What is the appropriate action?

  1. Test the assembly again using the reported serial number
  2. Delete the assembly from the inventory
  3. Accept the report because the test passed
  4. Return the report for correction and verify the assembly identification Correct answer.

Explanation

Accurate identification links test results to the correct assembly in the inventory. A mismatch must be corrected and verified before the report is accepted.

Question 18Cross-Connection Control Program Administration

Which practice best supports public awareness of a cross-connection control program?

  1. Publishing program requirements and backflow prevention tips on the utility website and in billing inserts Correct answer.
  2. Sharing customer test results with neighboring utilities
  3. Keeping program details confidential to avoid liability
  4. Removing hazard information from new customer packets

Explanation

Public education helps customers understand why assemblies are required and how to comply with testing deadlines. Outreach through websites and billing materials is a low-cost, effective method.

Question 19Cross-Connection Control Program Administration

A program administrator is drafting procedures for responding to a reported cross connection. Which sequence is most logical?

  1. Investigate and confirm the hazard, notify the customer, require correction, and verify compliance Correct answer.
  2. Require correction without documenting the hazard
  3. Terminate service, then investigate, then notify the customer
  4. Notify the state, then wait for the customer to call

Explanation

Sound procedure moves from investigation and confirmation to written notification, a required correction with a deadline, and verification that the correction was made. Documentation supports each step.

Question 20Cross-Connection Control Program Administration

A utility serves a customer whose private well can be cross-connected to the public supply through a shared piping system. What is the primary risk?

  1. Increased water bills for the customer
  2. Reduced fire flow capacity
  3. Corrosion of the customer's water heater
  4. Contamination from the private well entering the public main Correct answer.

Explanation

A private well or auxiliary supply can introduce contaminants of unknown quality into the public system if the two supplies are interconnected. An approved assembly or a complete physical separation is required.

Question 21Cross-Connection Control Program Administration

A program uses a risk ranking matrix for customer premises. Which combination should rank highest?

  1. Low toxicity chemical with no backpressure potential
  2. High toxicity chemical with continuous backpressure potential Correct answer.
  3. Aesthetic contaminant with intermittent use
  4. Non-health hazard with an air gap installed

Explanation

Risk ranking weighs both hazard severity and the likelihood of reversal. A high-toxicity substance combined with continuous backpressure potential represents the greatest combined risk.

Question 22Cross-Connection Control Program Administration

An administrator must decide whether a containment assembly is required for a two-unit duplex with no irrigation, no pools, and no chemical processes. Which conclusion is best supported?

  1. Containment may not be required because no significant hazard is identified Correct answer.
  2. Containment is prohibited for residential properties
  3. Containment is required because all residential services need it
  4. Containment is required only if the owner requests it

Explanation

Containment requirements are driven by identified hazards rather than by occupancy type alone. Where a survey finds no significant hazard, the program may document that finding and forgo a containment assembly.

Question 23Cross-Connection Control Program Administration

A utility discovers that several testers are certifying assemblies they never actually tested. What is the most effective program-level corrective action?

  1. Raise the testing fee to discourage volume
  2. Stop requiring annual testing
  3. Verify tester certification and audit a sample of submitted reports against field records Correct answer.
  4. Accept only reports submitted by mail

Explanation

Fraudulent reports undermine the entire program, so the administrator should confirm tester credentials and audit reports against field verification. Deterrence comes from credible oversight rather than from pricing.

Question 24Cross-Connection Control Program Administration

A water system adds a new pressure zone that raises distribution pressure substantially. How does this change affect the cross-connection control program?

  1. It has no effect on backflow risk
  2. It eliminates the need for containment assemblies
  3. Higher supply pressure may increase the consequences of failure and should prompt review of assembly ratings and relief discharge capacity Correct answer.
  4. Higher supply pressure reduces backpressure risk

Explanation

Higher distribution pressure increases the energy available during a reversal and can affect assembly pressure ratings and relief valve discharge. The program should re-evaluate assembly selection and installation conditions in the affected zone.

Question 25Cross-Connection Control Program Administration

A program administrator must justify the budget for cross-connection control to a governing board. Which argument best supports continued funding?

  1. The program generates revenue through testing fees
  2. The program prevents contamination events whose health and remediation costs far exceed program costs Correct answer.
  3. The program is required only for large utilities
  4. The program reduces the need for water treatment

Explanation

The strongest justification is risk avoidance: a single contamination event can cause illness, costly remediation, and loss of public trust far exceeding routine program expenses. Framing the program as prevention supports sustained investment.

Question 26Cross-Connection Control Program Administration

Which document gives a cross-connection control program its legal authority to require backflow prevention assemblies on customer premises?

  1. The utility's annual consumer confidence report
  2. The utility's approved cross-connection control ordinance or local code Correct answer.
  3. The tester's certification card
  4. The assembly manufacturer's installation manual

Explanation

Enforcement authority comes from a formally adopted ordinance, rule, or plumbing code that the governing body has approved. Without that legal basis, a utility can advise customers but cannot compel installation, testing, or removal of a cross connection.

Question 27Cross-Connection Control Program Administration

A program administrator is choosing how often to require testing of reduced pressure principle assemblies. Which approach best reflects standard program practice?

  1. Test every assembly only when the utility changes its source water
  2. Test only when the customer reports a malfunction
  3. Require annual testing, with more frequent testing where local rules or hazard conditions justify it Correct answer.
  4. Test each assembly once at installation and never again

Explanation

Most programs require at least annual testing of reduced pressure principle assemblies because mechanical check components can foul or fail silently. Local rules or high-hazard conditions may shorten the interval, and testing must be performed by an approved tester with results submitted to the program.

Question 28Cross-Connection Control Program Administration

A program administrator wants to track which assemblies are overdue for testing. Which record-keeping element is most useful for that purpose?

  1. The tester's calibration certificates filed by calendar year
  2. Copies of the utility's rate schedule for backflow testing fees
  3. The original plumbing permit drawings for each building
  4. A database listing each assembly with its location, hazard level, and last test date Correct answer.

Explanation

An inventory database keyed to each assembly's location, hazard classification, and most recent test date lets staff generate overdue lists and schedule follow-up. Permit drawings and fee schedules do not by themselves show current compliance status.

Question 29Cross-Connection Control Program Administration

A utility learns that a large industrial customer has added an unapproved chemical feed line connected to process water that also serves a break room. What is the most appropriate first program action?

  1. Wait for the next scheduled annual survey to note the finding
  2. Refer the matter to the manufacturer of the chemical feed equipment
  3. Send the customer a general brochure about backflow prevention
  4. Issue an immediate notice requiring correction and, if warranted, secure the service until the hazard is eliminated Correct answer.

Explanation

An unapproved cross connection involving a health hazard calls for prompt written notice and, where the local ordinance allows, termination or restriction of service until the condition is corrected. Delay or general education is inadequate when contamination could reach potable water used by employees.

Question 30Cross-Connection Control Program Administration

A program administrator must decide whether to hire a full-time backflow coordinator. Which argument most directly supports the position to a governing board?

  1. A coordinator would allow the utility to stop enforcing its ordinance during periods of staff shortage
  2. A coordinator would eliminate the need for customer surveys and tester certification
  3. A coordinator would replace the need for approved testers in the field
  4. A dedicated coordinator improves tracking of assembly inventories and test compliance, reducing the utility's exposure to contamination incidents and regulatory penalties Correct answer.

Explanation

The strongest justification ties the position to measurable program outcomes: accurate inventories, timely test follow-up, and reduced risk of contamination and enforcement action. Claims that a coordinator removes other required functions misstate how a program operates.

Question 31Hydraulics and Backflow Principles

In a cross-connection control context, backflow is best described as which of the following?

  1. The loss of pressure caused by friction inside a pipe
  2. The accumulation of scale on the interior of a water main
  3. The normal forward flow of water toward a fixture outlet
  4. The reverse flow of water or other substances into the potable water system Correct answer.

Explanation

Backflow is any reversal of the intended direction of flow that allows nonpotable water or other substances to enter the potable piping. It can be driven by pressure differences in either direction, so the defining feature is reverse flow into the supply, not merely a pressure or quality change.

Question 32Hydraulics and Backflow Principles

Backsiphonage occurs when which condition develops in the supply piping?

  1. A closed valve downstream of a meter
  2. A negative or sub-atmospheric pressure in the supply line Correct answer.
  3. An increase in supply pressure above the fixture outlet
  4. A rise in water temperature within a storage tank

Explanation

Backsiphonage is backflow caused by a reduction of supply pressure to below atmospheric, which draws contaminated water into the system. The driving force is the pressure differential created by the negative pressure, not by a pump or elevated downstream pressure.

Question 33Hydraulics and Backflow Principles

Which condition is the direct cause of backpressure backflow?

  1. An open drain valve on a water heater
  2. A vacuum created by a broken water main
  3. A sudden drop in atmospheric pressure at the site
  4. Downstream pressure that exceeds the pressure in the supply main Correct answer.

Explanation

Backpressure backflow results when the pressure on the downstream side of a cross-connection rises above the supply pressure, pushing water backward. Typical sources include pumps, boilers, and elevated tanks that raise downstream pressure above the main pressure.

Question 34Hydraulics and Backflow Principles

What is the purpose of an air gap in a plumbing system?

  1. To increase the flow rate at a fixture outlet
  2. To filter sediment from the potable supply
  3. To reduce noise from water hammer in the piping
  4. To provide a physical separation between a potable outlet and the flood-level rim of a receptor Correct answer.

Explanation

An air gap is the unobstructed vertical distance between the lowest point of a potable water outlet and the flood-level rim of the receiving vessel. That physical separation prevents any contact between the supply and the potentially contaminated receptor, making it the most reliable form of protection.

Question 35Hydraulics and Backflow Principles

Which device is designed to protect against both backsiphonage and backpressure and is typically used on continuous-pressure applications such as boiler feed lines?

  1. Reduced pressure principle backflow prevention assembly Correct answer.
  2. Hose-bibb vacuum breaker
  3. Dual check valve assembly
  4. Atmospheric vacuum breaker

Explanation

A reduced pressure principle assembly contains two independently acting check valves plus a hydraulically operated differential relief valve. That relief valve opens if either check fails, so the assembly protects against both backsiphonage and backpressure and is approved for continuous pressure and hazardous applications.

Question 36Hydraulics and Backflow Principles

A pressure vacuum breaker assembly differs from an atmospheric vacuum breaker primarily because it can do which of the following?

  1. Operate under continuous supply pressure without discharging during normal flow Correct answer.
  2. Be installed below the flood-level rim of a fixture
  3. Serve as a testable device for high-hazard protection
  4. Protect against backpressure from a downstream pump

Explanation

A pressure vacuum breaker uses a spring-loaded check and an air inlet that stays closed under normal supply pressure, so it may be used on lines subject to continuous pressure. An atmospheric vacuum breaker cannot be subjected to continuous pressure and must not have downstream shutoff valves.

Question 37Hydraulics and Backflow Principles

A hose-bibb vacuum breaker is installed on an outdoor sill cock. Which condition will cause the device to function as intended?

  1. A downstream pump raising hose pressure above supply pressure
  2. A fully open hose nozzle during normal watering
  3. A closed shutoff valve upstream of the sill cock
  4. A drop in supply pressure that creates a partial vacuum in the hose Correct answer.

Explanation

A hose-bibb vacuum breaker opens its air inlet when supply pressure falls below atmospheric, breaking the siphon and admitting air. It is a backsiphonage-only device, so it responds to a pressure drop, not to downstream pressure that exceeds supply pressure.

Question 38Hydraulics and Backflow Principles

Which statement correctly describes the hydraulic principle that makes a reduced pressure principle assembly fail safe?

  1. The downstream check valve opens to drain the assembly during backflow
  2. The relief valve remains closed under all conditions to prevent discharge
  3. The differential relief valve opens whenever the pressure in the zone between the check valves rises above a set differential Correct answer.
  4. The upstream check valve closes whenever downstream flow stops

Explanation

The relief valve is held closed by supply pressure acting on its diaphragm and opens when the pressure in the intermediate zone approaches the supply pressure within a specified differential. This design ensures that a leaking or fouled check valve causes discharge rather than contamination of the supply.

Question 39Hydraulics and Backflow Principles

A testable double check valve assembly is installed on a fire sprinkler connection. Which statement best describes its protective capability?

  1. It protects against backsiphonage only and cannot resist backpressure
  2. It must be installed with an air gap to be effective
  3. It provides high-hazard protection equivalent to a reduced pressure assembly
  4. It protects against backpressure and backsiphonage but is limited to nonhazardous applications Correct answer.

Explanation

A double check valve assembly has two independently acting check valves and can protect against both backpressure and backsiphonage. Because it lacks a relief valve, it is restricted to nonhazard or low-hazard service where a failure of both checks would not create a serious health risk.

Question 40Hydraulics and Backflow Principles

Which factor most directly determines the degree of hazard assigned to a cross-connection?

  1. The distance from the meter to the fixture
  2. The static pressure of the supply main
  3. The diameter of the pipe at the cross-connection
  4. The nature of the contaminant and the potential health effect if it enters the supply Correct answer.

Explanation

Hazard classification depends on what could enter the system and how serious the resulting health effect would be. A toxic or disease-causing substance creates a high hazard, while a substance that only affects aesthetics or usability is a low hazard, regardless of pipe size or pressure.

Question 41Hydraulics and Backflow Principles

A facility has a submerged inlet in a tank holding a chemical that is toxic at low concentrations. Which protection method is most appropriate?

  1. An atmospheric vacuum breaker located at the tank rim
  2. A reduced pressure principle assembly or a properly sized air gap Correct answer.
  3. A dual check valve
  4. A hose-bibb vacuum breaker

Explanation

A toxic chemical represents a high hazard, which requires protection against both backsiphonage and backpressure. A reduced pressure principle assembly or a correctly sized air gap provides that level of protection, while the other listed devices are limited to lower hazards or to backsiphonage alone.

Question 42Hydraulics and Backflow Principles

Which condition must be met for an air gap to be considered an approved backflow protection method?

  1. The gap must equal the diameter of the receiving pipe
  2. The gap must be sealed with a flexible boot
  3. The gap must be at least twice the effective opening of the outlet and never less than one inch Correct answer.
  4. The gap must be at least six inches regardless of outlet size

Explanation

Plumbing codes require the air gap to be at least twice the effective opening of the discharge outlet, with a minimum of one inch, measured above the flood-level rim. The separation must remain unobstructed so that no physical connection can occur.

Question 43Hydraulics and Backflow Principles

A reduced pressure principle assembly is discharging water continuously from its relief valve. What is the most likely cause?

  1. A normal condition during periods of high demand
  2. A pressure drop in the supply main below atmospheric
  3. A fouled or failing first check valve allowing supply pressure into the intermediate zone Correct answer.
  4. A closed downstream shutoff valve with normal supply pressure

Explanation

Continuous relief discharge usually means the first check is not holding, allowing supply pressure to reach the intermediate zone and lift the relief valve. The assembly is doing its job by discharging rather than allowing contamination to pass, so the check must be inspected and serviced.

Question 44Hydraulics and Backflow Principles

Which statement about the installation of an atmospheric vacuum breaker is correct?

  1. It must be installed downstream of a pump to sense backpressure
  2. It may be installed below the flood-level rim if a check valve is added
  3. It must be installed at least six inches above the highest point of the downstream piping and have no downstream shutoff valve Correct answer.
  4. It may be used on a line subject to continuous pressure if it is testable

Explanation

An atmospheric vacuum breaker relies on gravity and atmospheric pressure, so it must be mounted above the highest downstream outlet and must not be subjected to continuous pressure. Downstream shutoff valves can trap pressure and defeat the device.

Question 45Hydraulics and Backflow Principles

In a water distribution system, which condition most directly reduces the available pressure at a fixture?

  1. An increase in pipe diameter along the run
  2. Friction loss along the piping plus elevation gain from the source Correct answer.
  3. The presence of a pressure gauge at the fixture
  4. A decrease in water temperature

Explanation

Available pressure at a fixture equals source pressure minus friction losses and minus the pressure equivalent of any elevation rise. Longer runs, fittings, and higher flow all increase friction loss, while raising the outlet reduces pressure by roughly 0.433 psi per foot of elevation.

Question 46Hydraulics and Backflow Principles

Approximately how much pressure does a column of water one foot high exert at its base?

  1. 8.34 psi
  2. 1.0 psi
  3. 0.433 psi Correct answer.
  4. 2.31 psi

Explanation

A one-foot column of water produces about 0.433 psi, which is the reciprocal of 2.31 feet per psi. This relationship is used constantly to convert between head in feet and pressure in psi in backflow and hydraulics work.

Question 47Hydraulics and Backflow Principles

A gauge at the base of a tank reads 34.7 psi. What is the approximate water depth above the gauge?

  1. 15 feet
  2. 80 feet Correct answer.
  3. 35 feet
  4. 150 feet

Explanation

Depth in feet equals pressure in psi multiplied by 2.31 feet per psi. Multiplying 34.7 by 2.31 gives approximately 80 feet, which is the static head corresponding to that gauge reading.

Question 48Hydraulics and Backflow Principles

Water flows through a pipe that narrows from a 4-inch section to a 2-inch section. According to continuity, what happens to the velocity in the smaller section?

  1. It remains the same because flow rate is constant
  2. It increases to about four times the velocity in the larger section Correct answer.
  3. It increases to about twice the larger-section velocity
  4. It decreases to about one-quarter of the larger-section velocity

Explanation

Continuity requires that flow rate equal area times velocity, so velocity varies inversely with cross-sectional area. Halving the diameter reduces area to one-quarter, so the velocity must rise to about four times its previous value.

Question 49Hydraulics and Backflow Principles

Which principle explains why a high-velocity stream can draw a contaminant into a flowing line?

  1. The contaminant is pushed by the static pressure of the main
  2. The weight of the contaminant exceeds the weight of water
  3. The pipe material absorbs the contaminant
  4. A local pressure reduction accompanies increased velocity in a constriction Correct answer.

Explanation

Where velocity increases through a constriction, local pressure falls, which can create a partial vacuum that aspirates liquid from a connected source. This is the same venturi effect that underlies many ejectors and some backflow scenarios.

Question 50Hydraulics and Backflow Principles

Which of the following is a typical consequence of thermal expansion in a closed potable water system with a backflow preventer installed?

  1. Flow rate increases at the meter
  2. Water temperature drops rapidly at the fixture
  3. Pressure rises because heated water cannot expand back into the main Correct answer.
  4. The backflow preventer opens its relief valve to relieve the pressure

Explanation

A check valve or backflow preventer can isolate the building from the main, so heated water has nowhere to expand and system pressure climbs. The usual remedy is a thermal expansion tank or a relief device rated for potable water.