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OBC Plumbing House practice questions

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Question 1Plumbing Terminology, Definitions, and Symbols

In plumbing terminology, what does the abbreviation 'WC' most commonly stand for on a floor plan?

  1. Waste connection
  2. Water column
  3. Water closet Correct answer.
  4. Wall coupling

Explanation

On plumbing drawings the abbreviation WC denotes a water closet, which is the trade term for a toilet fixture. The symbol appears wherever a toilet is scheduled or located. Recognizing it lets a reader interpret fixture layouts quickly.

Question 2Plumbing Terminology, Definitions, and Symbols

A plumber refers to the 'stack' in a drainage system. What does this term describe?

  1. A vertical pipe line carrying waste or soil Correct answer.
  2. A buried exterior leader
  3. A horizontal branch under a floor
  4. A short trap arm at a fixture

Explanation

A stack is the industry term for a main vertical pipe that carries soil or waste downward through a building. Horizontal runs are called branches, not stacks. The distinction matters because stack rules govern sizing, venting, and support.

Question 3Plumbing Terminology, Definitions, and Symbols

What does the term 'fixture unit' express in plumbing design?

  1. The physical weight of a fixture in kilograms
  2. The drainage load a fixture imposes relative to a base value Correct answer.
  3. The water pressure needed at a fixture outlet
  4. The number of fixtures on one branch

Explanation

A fixture unit is a dimensionless measure of the probable load a fixture places on the drainage or supply system, referenced to a base fixture value. Designers total fixture units to size pipes rather than counting fixtures alone. It accounts for how often and how much a fixture discharges.

Question 4Plumbing Terminology, Definitions, and Symbols

On a plumbing drawing a circle with a diagonal line through it placed on a pipe run typically indicates what?

  1. A valve that is normally closed Correct answer.
  2. A pipe passing through a wall
  3. A riser turning upward
  4. A cleanout location

Explanation

A circle with a diagonal line is a common schematic symbol for a valve shown in the closed position. Valve symbols generally show the normal operating state. Reading the symbol correctly prevents misjudging isolation points during service.

Question 5Plumbing Terminology, Definitions, and Symbols

What is the 'trap seal' in a plumbing fixture drain?

  1. The threaded nut securing the trap
  2. The vent pipe connected to the trap arm
  3. The slope of the trap arm
  4. The water depth retained in the trap to block sewer gas Correct answer.

Explanation

The trap seal is the body of water held in the trap's dip that blocks sewer gas from entering the building. Its depth is specified in codes because too little water allows gas passage and too much promotes clogging. The seal is replenished each time the fixture is used.

Question 6Plumbing Terminology, Definitions, and Symbols

A drawing note reads 'CW' beside a fixture supply. Which interpretation is correct?

  1. Circulating water
  2. Cold water Correct answer.
  3. Condensate water
  4. Chemical waste

Explanation

CW is the standard abbreviation for cold water on supply piping drawings, often paired with HW for hot water. Recognizing it prevents misconnecting fixtures to the wrong supply. The pairing appears on riser diagrams and fixture schedules.

Question 7Plumbing Terminology, Definitions, and Symbols

What does the plumbing term 'developed length' measure?

  1. The buried depth of a sewer line
  2. The vertical rise of a drain stack
  3. The length of pipe measured along its centerline including fittings Correct answer.
  4. The straight-line distance between two pipe ends

Explanation

Developed length is the measurement taken along the run of pipe following its centerline, accounting for changes in direction through fittings. Codes use it when limiting trap arm and vent lengths. Straight-line distance would understate the actual path.

Question 8Plumbing Terminology, Definitions, and Symbols

A 'backflow preventer' installed on a water supply serves which purpose?

  1. To filter sediment from the service line
  2. To stop contaminated water from reversing into the potable supply Correct answer.
  3. To absorb water hammer surges
  4. To increase supply pressure at upper floors

Explanation

A backflow preventer allows flow in one direction only, protecting the potable supply from contamination by reversal. Cross-connection control codes require them at specific hazards. They do not boost pressure or filter debris.

Question 9Plumbing Terminology, Definitions, and Symbols

In drainage terminology, what is a 'branch'?

  1. Any pipe that carries waste from fixtures to a stack or building drain Correct answer.
  2. The water service entering the building
  3. The main vertical pipe through the roof
  4. The vent terminal above the roof

Explanation

A branch is a pipe conveying waste from one or more fixtures to a stack, building drain, or other branch. It is distinguished from stacks by being non-vertical in the main. Branch sizing and venting rules follow from this definition.

Question 10Plumbing Terminology, Definitions, and Symbols

What is meant by the 'flood level rim' of a fixture?

  1. The edge over which water would overflow onto the floor Correct answer.
  2. The height of the fixture's supply stop
  3. The depth of the trap seal
  4. The lowest point of the fixture outlet

Explanation

The flood level rim is the uppermost edge of a fixture, the point at which water spills onto the floor. Code clearances and backflow air gaps are measured relative to it. It is a reference elevation, not a flow dimension.

Question 11Plumbing Terminology, Definitions, and Symbols

A plumbing plan shows a small triangle with the letter 'V' at the top of a vertical pipe. What does this most likely represent?

  1. A vertical drain riser
  2. A valve in a closed position
  3. A vent terminal through the roof Correct answer.
  4. A vacuum breaker on a hose bibb

Explanation

A triangle at the top of a riser commonly denotes a vent terminating through the roof. Vent terminals are shown because their location affects roof penetration and air intake distances. The letter V reinforces the vent identification.

Question 12Plumbing Terminology, Definitions, and Symbols

What does the term 'air gap' describe in plumbing?

  1. The unobstructed vertical distance between a supply outlet and the flood level rim Correct answer.
  2. The gap between a trap and the floor
  3. The clearance between a pipe and a joist
  4. The space inside a vent stack

Explanation

An air gap is the physical separation between a water outlet and the flood level rim of the receiving fixture, providing the highest form of backflow protection. Because it is a physical separation, it cannot fail like a mechanical device. Codes specify minimum distances.

Question 13Plumbing Terminology, Definitions, and Symbols

In plumbing vocabulary, what is a 'wye' fitting?

  1. A fitting that connects two pipes at 180 degrees
  2. A fitting that caps a pipe end
  3. A fitting with a branch leaving at an angle to the run Correct answer.
  4. A fitting that reduces pipe diameter in line

Explanation

A wye is a three-way fitting whose branch leaves the main run at an oblique angle, commonly used to join a branch into a drain in the direction of flow. The angled entry promotes smooth flow and reduces clogging. It is distinct from a tee, whose branch is at 90 degrees.

Question 14Plumbing Terminology, Definitions, and Symbols

A specification calls for 'schedule 40' pipe. What does the schedule number identify?

  1. The maximum working temperature
  2. The pipe's outside diameter in inches
  3. The pipe's wall thickness relative to its size Correct answer.
  4. The length of each pipe section

Explanation

The schedule number indicates nominal wall thickness for a given pipe size, with higher numbers meaning thicker walls. Wall thickness determines pressure rating along with material. Outside diameter stays constant for a nominal size across schedules.

Question 15Plumbing Terminology, Definitions, and Symbols

What does the term 'slope' or 'fall' mean for a horizontal drainage pipe?

  1. The offset between two parallel pipes
  2. The angle at which a vent leaves a stack
  3. The ratio of vertical drop to horizontal run Correct answer.
  4. The change in pipe diameter along the run

Explanation

Slope expresses the vertical drop per unit of horizontal run, driving gravity flow at a self-cleansing velocity. Too little slope causes solids to settle, while excessive slope can leave liquids behind. Codes set minimum and maximum values.

Question 16Plumbing Terminology, Definitions, and Symbols

A fixture schedule lists a 'lavatory'. Which fixture does this term denote?

  1. A laundry standpipe
  2. A water heater tank
  3. A handwashing sink in a bathroom Correct answer.
  4. A floor drain in a mechanical room

Explanation

In plumbing terminology a lavatory is the handwashing sink, distinguished from a sink used for other purposes. Schedules use the term so installers know which fixture and trim to supply. Confusing it with a water closet is a common error.

Question 17Plumbing Terminology, Definitions, and Symbols

In venting terminology, what is a 'wet vent'?

  1. A vent with a mechanical fan
  2. A vent pipe that carries rainwater
  3. A vent installed below the flood level rim
  4. A vent that also serves as a drain for fixtures on the same floor Correct answer.

Explanation

A wet vent is a pipe that performs both drainage and venting duties for fixtures on the same floor, permitted under specific code conditions. Because it carries waste, sizing and connection rules are stricter than for dry vents. The arrangement saves piping in compact layouts.

Question 18Plumbing Terminology, Definitions, and Symbols

What is the function of a 'cleanout' in a drainage system?

  1. To admit air into the drain for faster flow
  2. To measure flow through the pipe
  3. To provide access for clearing blockages in the line Correct answer.
  4. To separate grease from wastewater

Explanation

A cleanout is an accessible opening, usually capped or plugged, that lets a plumber rod or snake a drain line. Codes require them at specified intervals and at changes of direction. They are access points, not flow-control devices.

Question 19Plumbing Terminology, Definitions, and Symbols

A plan symbol shows a rectangle divided by a diagonal line inside a pipe run. What does this commonly indicate?

  1. A pump
  2. A strainer or filter Correct answer.
  3. A water meter
  4. A pressure-reducing valve

Explanation

A rectangle with an internal diagonal is a frequent schematic symbol for a strainer or filter element in a line. The diagonal suggests the screening surface within the housing. Identifying it helps technicians locate serviceable components.

Question 20Plumbing Terminology, Definitions, and Symbols

What does the term 'stack vent' refer to?

  1. A vent serving only a floor drain
  2. A vent that relieves pressure inside a water heater
  3. A separate vent run to the outdoors from a branch
  4. The extension of a soil or waste stack above the highest branch Correct answer.

Explanation

A stack vent is the continuation of a soil or waste stack above the highest connected fixture branch, open to the atmosphere. It relieves pressure in the stack so traps are not siphoned. It differs from a vent stack, which is a separate vertical vent.

Question 21General Regulations, Permits, and Inspections

Under a typical plumbing code, who is generally responsible for obtaining the permit before plumbing work begins on a house?

  1. The supplier that delivers the piping materials
  2. The plumbing inspector assigned to the district
  3. The real estate agent handling the sale
  4. The property owner or the licensed contractor hired for the job Correct answer.

Explanation

Permits are normally pulled by the owner of the property or by the licensed plumbing contractor engaged to perform the work. The inspector only reviews and approves the application, and suppliers or agents have no role in the permitting process. Starting work before the permit is issued is a violation in most jurisdictions.

Question 22General Regulations, Permits, and Inspections

A homeowner plans to replace a water heater in a single-family house. What is the most common permit requirement?

  1. No permit is needed because the work is a simple replacement
  2. A permit is only needed if the heater capacity increases
  3. A plumbing permit is required before the replacement is installed Correct answer.
  4. A permit is required only for commercial buildings

Explanation

Replacing a water heater is generally treated as regulated plumbing work that requires a permit, even when the size stays the same. The permit allows the inspector to verify relief valve piping, venting, and combustion air. Capacity changes and building type do not remove the requirement for a residence.

Question 23General Regulations, Permits, and Inspections

Which statement best describes the purpose of a plumbing rough-in inspection?

  1. It confirms the final fixtures are clean and operating
  2. It certifies the water meter has been installed by the utility
  3. It approves the landscaping drainage plan
  4. It verifies concealed piping and fittings before they are covered Correct answer.

Explanation

A rough-in inspection occurs after piping is installed but before walls, floors, or ceilings conceal it. The inspector checks pipe sizing, slope, support, and joint integrity while the work is still visible. Final fixture function is addressed at the final inspection instead.

Question 24General Regulations, Permits, and Inspections

When must a plumbing system be tested for the final inspection to be approved?

  1. Whenever the contractor chooses during construction
  2. After the building is occupied and fixtures are in use
  3. Only when the inspector requests a test on site
  4. Before the rough-in is concealed, using the approved test method Correct answer.

Explanation

Drain, waste, and vent piping must be tested before concealment, using the method the code specifies, such as a water or air test. Passing this test is a condition for rough-in approval and later final approval. Testing after occupancy or at the contractor's discretion does not satisfy the requirement.

Question 25General Regulations, Permits, and Inspections

What is the usual consequence when plumbing work requiring a permit is started without one?

  1. The contractor receives a permanent license suspension
  2. The property is exempt from future inspections
  3. The jurisdiction may require a penalty fee and a special inspection Correct answer.
  4. The work is automatically accepted if it passes inspection

Explanation

Unpermitted work typically triggers penalty fees, a required permit application, and sometimes a special inspection to expose concealed work. Passing an inspection does not erase the violation. Automatic acceptance and permanent license loss are not standard outcomes.

Question 26General Regulations, Permits, and Inspections

Which document typically authorizes an inspector to enter a property to perform a plumbing inspection?

  1. A copy of the manufacturer's installation manual
  2. A receipt from the plumbing supply store
  3. A verbal invitation from any neighbor
  4. The issued permit and the inspection request Correct answer.

Explanation

The permit and the request for inspection establish the legal basis for the inspector to examine the permitted work. Inspectors are not authorized to enter based on a neighbor's invitation. Purchase receipts and installation manuals support the review but do not grant access.

Question 27General Regulations, Permits, and Inspections

A contractor wants to begin installing underground drain piping before the permit is issued. What is the correct action?

  1. Wait until the permit is issued and any required inspections are scheduled Correct answer.
  2. Install only the portion that will be buried deepest
  3. Ask the supplier to confirm the pipe size first
  4. Install the piping and request an inspection the same day

Explanation

Work may not proceed until the permit has been issued, and underground piping must be inspected before backfill. Proceeding early exposes the contractor to stop-work orders and penalties. Pipe size confirmation from a supplier does not substitute for a permit.

Question 28General Regulations, Permits, and Inspections

An inspector finds that a drain line was backfilled before the underground inspection was performed. What is the most likely required remedy?

  1. The contractor must expose the piping for inspection at their own cost Correct answer.
  2. The building department waives the inspection for small projects
  3. The inspector issues final approval based on photographs
  4. The work is accepted if the pipe is schedule 40

Explanation

Piping covered before inspection must be uncovered so the inspector can verify slope, joints, and bedding. The cost of exposing and restoring the work falls on the party responsible. Photographs and material type do not replace a required inspection.

Question 29General Regulations, Permits, and Inspections

A plumbing plan shows a new bathroom added to a house. When should the permit application generally be submitted?

  1. Only after the framing inspection passes
  2. After the fixtures are delivered to the site
  3. Before any construction or plumbing work begins Correct answer.
  4. At the same time as the certificate of occupancy is requested

Explanation

The permit application must be submitted and the permit issued before construction begins. Applying after framing or at occupancy would mean work proceeded without authorization. Fixture delivery timing has no effect on when the permit is required.

Question 30General Regulations, Permits, and Inspections

During a final inspection, an inspector finds a missing access panel for a concealed bathtub waste and overflow assembly. What is the appropriate outcome?

  1. Immediate revocation of the contractor's license
  2. A correction notice requiring the access to be provided before approval Correct answer.
  3. Final approval with a note to correct it later
  4. Approval because the tub drains properly

Explanation

Concealed connections that require service access must have an accessible panel, and its absence is a correctable code deficiency. The inspector issues a notice listing the item to be fixed and re-inspected. License revocation is far beyond the scope of a single correction.

Question 31General Regulations, Permits, and Inspections

A contractor plans to pressure-test a DWV system with air instead of water. What should the contractor confirm before testing?

  1. That the code and the inspector allow the chosen test method and pressure Correct answer.
  2. That the water heater is operating
  3. That the building is fully occupied
  4. That all fixtures are already installed

Explanation

The code specifies acceptable test media and pressures, and some jurisdictions restrict air testing because of its stored energy. The contractor must confirm the method is permitted and follow the required pressure and duration. Occupancy, heater operation, and fixture installation are unrelated to test validity.

Question 32General Regulations, Permits, and Inspections

Who may typically perform plumbing work that requires a permit on a residential project?

  1. Any person supervised by the homeowner
  2. Any employee of the general contractor
  3. A licensed plumbing contractor or a homeowner on their own residence where allowed Correct answer.
  4. Only a licensed engineer

Explanation

Plumbing work is generally limited to licensed contractors, though many jurisdictions allow an owner to work on their own single-family residence after meeting local conditions. General contractor employees and unlicensed helpers may not perform regulated plumbing. A licensed engineer is not automatically a plumbing installer.

Question 33General Regulations, Permits, and Inspections

A plan review comment requires a larger vent through the roof. What should the contractor do before installing the revised vent?

  1. Revise the plans or obtain approval for the change, then install as approved Correct answer.
  2. Install the larger vent without notifying the department
  3. Install the original vent and dispute the comment later
  4. Ask the supplier which size is in stock

Explanation

Changes from approved plans require revised documents or written approval so the record matches what is built. Installing the original design would contradict the review comment, and installing without notice leaves the file inconsistent. Stock availability does not govern code compliance.

Question 34General Regulations, Permits, and Inspections

A plumbing permit was issued with an expiration date, and no inspections have occurred. What generally happens if the work is not commenced or inspected within the stated period?

  1. The permit may expire and require renewal or a new application Correct answer.
  2. The permit remains valid indefinitely
  3. The permit transfers to the next owner without action
  4. The permit converts automatically to a certificate of occupancy

Explanation

Permits carry expiration provisions, and a permit that lapses generally must be renewed or reapplied for, sometimes with additional fees. It does not remain valid forever or convert into an occupancy certificate. Transfer to a new owner does not revive an expired permit.

Question 35General Regulations, Permits, and Inspections

An inspector requests that a test tee be exposed for verification of a building drain test. The contractor believes the test already passed. What is the appropriate response?

  1. Cover the tee permanently to protect it
  2. Refuse the request because the test was recorded
  3. Submit a letter stating the test passed
  4. Comply with the request so the inspector can verify the test Correct answer.

Explanation

The inspector has authority to verify that required tests were properly conducted, and cooperation avoids a failed or delayed inspection. Refusing or substituting paperwork for access can result in a correction notice. Permanently covering the tee would defeat the verification.

Question 36General Regulations, Permits, and Inspections

Which situation most clearly requires a new permit rather than a routine repair?

  1. Snaking a clogged kitchen drain
  2. Tightening a loose supply connection
  3. Replacing a worn faucet washer
  4. Adding a new branch drain and vent for a relocated sink Correct answer.

Explanation

Adding new drain and vent piping changes the plumbing system and requires a permit and inspection. Simple maintenance such as clearing a clog, tightening a connection, or replacing a washer is normally exempt. The distinction rests on whether new piping is installed.

Question 37General Regulations, Permits, and Inspections

A contractor installs plumbing in a house and the inspector issues a correction notice listing three deficiencies. What must happen before the final inspection can be approved?

  1. The inspector must approve the work as-is after 30 days
  2. The contractor must pay a fee instead of making corrections
  3. The contractor must correct the items and request a re-inspection Correct answer.
  4. The homeowner must sign a waiver of the deficiencies

Explanation

Correction notices identify code deficiencies that must be fixed and then verified by re-inspection. Fees or waivers do not substitute for correcting life-safety or code violations. Approval does not happen automatically after time passes.

Question 38General Regulations, Permits, and Inspections

A general contractor wants to cover drywall over new DWV piping the same afternoon, before the rough-in inspection. Which reasoning best reflects the code requirement?

  1. Covering is acceptable if the permit has been paid for
  2. Covering is acceptable if the plumber personally inspected the joints
  3. Covering must wait until the rough-in inspection approves the piping Correct answer.
  4. Covering is acceptable because drywall is not a plumbing material

Explanation

Concealed piping must be inspected and approved before it is covered, because the inspector cannot later verify joints, slope, and support. A plumber's self-inspection does not satisfy the requirement. Paying for a permit is not the same as passing the required inspection.

Question 39General Regulations, Permits, and Inspections

A homeowner performs plumbing work on their own single-family home and later sells it. During a pre-sale inspection, unpermitted alterations are discovered. What is the most likely regulatory consequence?

  1. The buyer automatically assumes all liability and no action is needed
  2. The seller may be required to permit and inspect the work or restore it to code Correct answer.
  3. The alterations become legal because the home changed ownership
  4. The building department must accept the work without review

Explanation

Unpermitted alterations remain a violation regardless of sale, and the responsible party typically must obtain permits, expose work for inspection, or remove noncompliant installations. Ownership transfer does not legalize the work. Buyers do not automatically absorb the regulatory obligation.

Question 40General Regulations, Permits, and Inspections

An inspector observes that a plumbing permit lists a 40-gallon water heater but a 50-gallon unit with a different vent configuration has been installed. What is the most appropriate course of action?

  1. Require removal of the heater regardless of venting
  2. Require a revised permit or approval reflecting the actual installation Correct answer.
  3. Approve it because the larger heater is an upgrade
  4. Ignore the difference if the heater works

Explanation

The permit and approved plans must match the installation, and a different heater with altered venting affects combustion air and vent sizing. The contractor should submit revised information for approval and inspection. A larger unit is not automatically acceptable, and removal is not required if the change can be properly approved.

Question 41Drainage, Waste, and Vent Systems

What is the minimum liquid capacity of a water closet tank in a new residential installation?

  1. 2.5 gallons per flush
  2. 1.6 gallons per flush Correct answer.
  3. 3.5 gallons per flush
  4. 5 gallons per flush

Explanation

Modern plumbing codes limit water closets installed in new construction to a maximum flush volume of 1.6 gallons, which effectively establishes that as the standard tank capacity. Older 3.5- and 5-gallon fixtures are permitted only as replacements in existing installations in some jurisdictions.

Question 42Drainage, Waste, and Vent Systems

What is the primary purpose of a vent in a drainage system?

  1. To increase the velocity of wastewater flow
  2. To filter grease from the waste stream
  3. To supply air for combustion appliances
  4. To protect trap seals from siphonage and back pressure Correct answer.

Explanation

A vent admits air to the drainage system so that pressure in the pipe stays near atmospheric, which protects trap seals from siphonage and back pressure. Without adequate venting, slugs of water can pull or push the seal out of a trap and allow sewer gas into the building.

Question 43Drainage, Waste, and Vent Systems

What is the minimum required slope for a horizontal drain of 3 inches diameter?

  1. 1/8 inch per foot Correct answer.
  2. 1/16 inch per foot
  3. 1/4 inch per foot
  4. 1/2 inch per foot

Explanation

Code permits 3-inch and larger horizontal drains to be installed at a slope of 1/8 inch per foot, provided the pipe is sized accordingly. Smaller pipe, such as 1-1/2 and 2 inch, must be sloped at 1/4 inch per foot to maintain self-cleansing velocity.

Question 44Drainage, Waste, and Vent Systems

A trap seal must be maintained at what minimum depth?

  1. 6 inches
  2. 4 inches
  3. 2 inches Correct answer.
  4. 1 inch

Explanation

Every trap must provide a liquid seal of at least 2 inches and no more than 4 inches of depth. The minimum depth resists evaporation and pressure fluctuation, while the maximum prevents excessive seal weight and sluggish flow.

Question 45Drainage, Waste, and Vent Systems

What is the purpose of a cleanout in a drainage system?

  1. To provide access for clearing blockages in the drain Correct answer.
  2. To relieve pressure from the vent stack
  3. To introduce air into the drainage system
  4. To measure flow volume in the building drain

Explanation

A cleanout is an accessible fitting with a removable cap that allows a plumber to rod or auger a blockage in the drain. It is required at the base of stacks, at changes in direction, and at intervals along horizontal drains.

Question 46Drainage, Waste, and Vent Systems

Which of these fixtures is required to be connected to a vent?

  1. A floor drain in a garage
  2. A water closet with a siphon-jet bowl
  3. A laundry sink with a 2-inch trap Correct answer.
  4. A drinking fountain drain

Explanation

Every trap-controlled fixture must be vented unless it is specifically exempted, and a laundry sink trap requires a vent. Water closets are vented through the stack or a relief vent, and floor drains and drinking fountains also require venting, so the correct answer must be examined against the specific exemption rules.

Question 47Drainage, Waste, and Vent Systems

What is the minimum size of a building sewer serving a single dwelling?

  1. 4 inches
  2. 1-1/2 inches
  3. 2 inches
  4. 3 inches Correct answer.

Explanation

The building sewer for a single dwelling must be at least 3 inches in diameter to carry the combined waste load and to allow proper cleaning. Smaller sizes are permitted only for specific branch drains, not for the main building sewer.

Question 48Drainage, Waste, and Vent Systems

What does the term 'developed length' mean in vent sizing?

  1. The horizontal distance between the fixture and the stack
  2. The total length of pipe measured along its centerline including fittings Correct answer.
  3. The inside diameter of the vent pipe
  4. The vertical rise of the vent above the roof

Explanation

Developed length is the measured length of the vent run along the pipe centerline, including the equivalent lengths of fittings. It is used with the fixture drain size to determine the required vent diameter from the sizing tables.

Question 49Drainage, Waste, and Vent Systems

A 4-inch horizontal drain runs 40 feet at 1/8 inch per foot. What is the total fall over that run?

  1. 20 inches
  2. 10 inches
  3. 5 inches Correct answer.
  4. 2-1/2 inches

Explanation

Fall equals slope multiplied by run length: 1/8 inch per foot times 40 feet equals 5 inches. This is the vertical drop from the upstream end to the downstream end of the drain.

Question 50Drainage, Waste, and Vent Systems

Which fitting is required where a horizontal drain changes from horizontal to vertical?

  1. A short-sweep 1/4 bend
  2. A long-sweep 1/4 bend
  3. A double sanitary tee
  4. A sanitary tee Correct answer.

Explanation

A sanitary tee is used where a horizontal branch connects to a vertical stack, directing flow downward with a gentle sweep. Long-sweep bends are used for horizontal-to-horizontal or vertical-to-horizontal changes where smooth flow is needed.