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Question 1General Regulations, Administration and Definitions

In a jurisdiction that enforces a model plumbing code, when must a plumbing permit be obtained for a new installation?

  1. Within 10 working days after the work has been started
  2. After the rough-in piping has been inspected and approved
  3. Whenever the authority having jurisdiction requests one in writing
  4. Before the work is started Correct answer.

Explanation

The permit is the administrative authorization to begin regulated plumbing work, so it must be issued before the work starts. This sequence lets the plumbing official inspect the installation at the required stages, including before concealment.

Question 2General Regulations, Administration and Definitions

As used in plumbing codes, the term “approved” means:

  1. Installed by a licensed master plumber
  2. Certified by a nationally recognized testing laboratory
  3. Manufactured in accordance with an ASTM standard
  4. Acceptable to the authority having jurisdiction Correct answer.

Explanation

“Approved” is defined by the relationship to the plumbing official: it means acceptable to the authority having jurisdiction, who may rely on listing, test data, or field evaluation. Being listed or built to a standard is a way to gain acceptance, not the definition itself.

Question 3General Regulations, Administration and Definitions

Which statement best defines potable water in the plumbing code?

  1. Water delivered through a public water main
  2. Water that has passed through a carbon filter
  3. Water that has been softened and chlorinated before use
  4. Water free of harmful amounts of impurities Correct answer.

Explanation

Potable water is water free from impurities in amounts sufficient to cause disease or harmful physiological effects, and it must meet the quality requirements of the health authority. The source or the treatment method does not establish potability; the water quality does.

Question 4General Regulations, Administration and Definitions

An air gap, as defined in the plumbing code, is:

  1. The unobstructed vertical distance through free air between an outlet and the flood level rim Correct answer.
  2. The annular clearance required where a pipe passes through a floor sleeve or wall penetration
  3. The vertical distance measured between the crown weir of a trap and the top of the trap dip
  4. A screened or hooded opening installed at the top of a vent stack to exclude rain and birds

Explanation

An air gap is the physical separation between the lowest point of a water supply outlet and the flood level rim of the receptor it serves. Because it relies only on open space, it is the most reliable form of backflow protection; codes set its minimum dimension by the effective opening of the outlet.

Question 5General Regulations, Administration and Definitions

In the text of a plumbing code, the word “shall” indicates a provision that is:

  1. Enforceable only after a complaint is filed
  2. Permissive and optional
  3. Mandatory Correct answer.
  4. Recommended as good practice

Explanation

Model codes use “shall” for mandatory requirements and “may” for permissive provisions. Recognizing this convention is essential because only mandatory provisions can be enforced as code violations.

Question 6General Regulations, Administration and Definitions

A buried supply line bursts at night and floods a homeowner's basement. The plumber makes the repair immediately. What does the code require regarding the permit?

  1. The owner must obtain the permit in the owner's name only
  2. The plumber must wait for a permit before shutting off the water
  3. A permit must be applied for promptly after the repair Correct answer.
  4. No permit is ever required for repair work on an existing system

Explanation

Codes allow emergency repairs to proceed before a permit is issued so that health and property are protected, but the permit application must follow promptly and the work remains subject to inspection. The emergency rule adjusts timing only; it does not remove the work from code coverage.

Question 7General Regulations, Administration and Definitions

A plumber has finished the drain, waste, and vent piping inside a new wall and is ready to close the wall. What must happen first?

  1. The plumber must record the completed work in the final certificate of occupancy
  2. The rough-in must be inspected and approved Correct answer.
  3. The water supply must be pressurized and the building occupied
  4. The wall covering must be installed so the inspector can judge the finished condition

Explanation

Piping and components that will be concealed must be tested and inspected before they are covered. Once the wall is closed, the inspector cannot verify joints, slope, and support, so covering early typically results in a correction notice requiring the covering to be removed.

Question 8General Regulations, Administration and Definitions

A cross-connection is best described as:

  1. The point where a building drain connects to the public sewer lateral
  2. A joint between two dissimilar piping materials that requires a dielectric fitting
  3. Any connection between potable water piping and a source of contamination Correct answer.
  4. A branch that ties two vent stacks together above the highest fixture served

Explanation

A cross-connection is any actual or potential link between a potable water system and any nonpotable source, which could let backflow carry contamination into drinking water. Cross-connections must be eliminated or protected by an approved backflow preventer.

Question 9General Regulations, Administration and Definitions

A drainage fixture unit is a measure of:

  1. The supply flow rate of a fixture expressed in gallons per minute
  2. The probable load a fixture adds to the drainage system Correct answer.
  3. The volume of water a fixture holds when filled to the rim
  4. The number of fixtures that may connect to one vent stack

Explanation

Fixture units convert the intermittent discharge of different fixture types into a common numerical load so that drain and vent sizes can be computed. One fixture unit approximates the discharge of a lavatory or similar small fixture.

Question 10General Regulations, Administration and Definitions

When sizing a water supply pipe, “developed length” is measured:

  1. Around the outside of each fitting plus the bodies of all valves
  2. Vertically from the lowest fixture to the highest fixture served
  3. In a straight line from the meter to the farthest fixture served
  4. Along the centerline of the pipe and fittings Correct answer.

Explanation

Developed length follows the actual run of pipe, including the allowance for fittings, so it is longer than a straight-line measurement and better reflects the friction loss in the piping. Using it produces a more accurate pipe size.

Question 11General Regulations, Administration and Definitions

A contractor proposes a plumbing material that is not specifically named in the code. Under what condition may the authority having jurisdiction approve it?

  1. When the material costs less than the material specified in the code
  2. When the contractor has already used the material in another state
  3. When it is shown to be equivalent in safety, durability, and performance Correct answer.
  4. When the manufacturer supplies a brochure describing the product

Explanation

Codes permit alternative materials and methods when the authority having jurisdiction finds them equivalent to the prescribed ones in quality, strength, effectiveness, fire resistance, durability, and safety. The burden of proving that equivalency rests on the person proposing the alternative.

Question 12General Regulations, Administration and Definitions

A plumbing contractor disagrees with an interpretation issued by the plumbing inspector. What is the usual administrative remedy?

  1. Ask the property owner to sign a liability waiver covering the work
  2. Ask the manufacturer to certify that the installation complies
  3. Disregard the interpretation and build the system as originally designed
  4. Appeal the decision to the board of appeals Correct answer.

Explanation

Administrative provisions establish a board of appeals or equivalent body to hear appeals of decisions made by the authority having jurisdiction, and the appeal must be filed within the time stated in the code. Any stay of enforcement is granted only as the code provides.

Question 13General Regulations, Administration and Definitions

A plumbing inspector finds work under way without a permit and in a condition that creates an immediate hazard. The inspector's typical authority is to:

  1. Revoke the contractor's license on the spot
  2. Issue a written stop-work order Correct answer.
  3. Refuse to conduct any future inspections at the property
  4. File criminal charges without a hearing

Explanation

The plumbing official may order work stopped when it is contrary to the code or is being performed without a required permit, and the order is issued in writing describing the conditions to be corrected. Work may not resume until the cited conditions are resolved.

Question 14General Regulations, Administration and Definitions

A newly installed water heater and water distribution system are complete and ready to operate. When may the plumbing be placed in service?

  1. After the system has been inspected and approved Correct answer.
  2. As soon as the water is turned on and no leaks appear
  3. When the plumber submits a signed invoice to the building owner
  4. As soon as the permit application has been filed with the city

Explanation

Plumbing systems must be tested and approved by the authority having jurisdiction before being placed in operation, and final approval is the administrative link between completion and lawful use. Putting an unapproved system into service can invalidate the permit and require re-inspection.

Question 15General Regulations, Administration and Definitions

How does a newly adopted plumbing code generally apply to plumbing that was lawfully installed years earlier in an existing building?

  1. All such plumbing must be upgraded to the new code within one year
  2. Only the drain piping must be replaced to match the new code
  3. It may remain in use unless it creates an unsafe condition Correct answer.
  4. The plumbing is unlawful until it is permitted and inspected again

Explanation

Plumbing codes are not retroactive: an existing system that was lawfully installed may continue in use, and the current code governs when the system is altered, repaired, or replaced. Conditions the authority finds unsafe or unsanitary may still be ordered corrected.

Question 16General Regulations, Administration and Definitions

The authority having jurisdiction may grant a modification of a code requirement only when:

  1. The modification lowers the installed cost without changing the layout
  2. The contractor holds a current license and has a surety bond on file with the city
  3. Strict compliance is impractical and safety is not reduced Correct answer.
  4. The owner signs a notarized statement accepting all risk for the installation

Explanation

Modification and variance provisions require a finding that practical difficulty makes literal compliance impractical and that the alternative conforms to the intent and purpose of the code while not reducing health, safety, or fire protection. The authority is exercised case by case, not as a general waiver.

Question 17General Regulations, Administration and Definitions

A plumbing plan is reviewed and approved, but the installed work departs from the plan and violates the code. Who is responsible?

  1. The building owner, because the owner signed the permit application
  2. No one, because the approved plan sets the standard for the job
  3. The plan reviewer, because plan approval certified compliance
  4. The permit holder who installed the work Correct answer.

Explanation

Approval of plans and specifications is an administrative review and does not relieve the permit holder or installer of the duty to comply with the code. Responsibility for how the work is actually installed stays with the party performing it.

Question 18General Regulations, Administration and Definitions

A building is converted from a warehouse into a restaurant. What does the plumbing code generally require of the plumbing system?

  1. It must be brought into compliance with the requirements for the new use Correct answer.
  2. Nothing, because plumbing already in place is grandfathered
  3. Only the water heater must be replaced with a larger unit
  4. Only an additional permit fee is owed, with no change to the piping

Explanation

A change of occupancy requires the plumbing to comply with the requirements applicable to the new use, because the new occupancy imposes different fixture, venting, and waste-loading demands. The authority may require additional fixtures and appurtenances before the space is occupied.

Question 19General Regulations, Administration and Definitions

For a large commercial project, the plumbing code typically allows the authority having jurisdiction to require:

  1. The owner to prepay all inspection costs by cashier's check before review
  2. Plans and specifications to be submitted before a permit is issued Correct answer.
  3. The plumber to purchase materials only from suppliers located in the city
  4. The contractor to be personally present at every inspection held on the site

Explanation

Where the scope or complexity of the work warrants it, the authority may require plans, specifications, and other data to be submitted for review before a permit is issued. The review verifies code compliance, but it does not relieve the installer of responsibility for the finished work.

Question 20General Regulations, Administration and Definitions

The flood level rim of a fixture is used to establish which of the following?

  1. The slope required for the branch drain that serves that particular fixture
  2. The required air gap or backflow protection for a supply outlet Correct answer.
  3. The number of fixture units that the code assigns to that type of fixture
  4. The minimum size of the fixture drain and its associated trap arm

Explanation

The flood level rim is the edge of the receptor from which water would overflow, so it is the reference elevation for an air gap and for the flood-level relationship of other backflow protection. The air gap is measured between the lowest outlet opening and that rim.

Question 21Plumbing Math and Pipe Sizing Calculations

How many cubic inches are contained in one cubic foot?

  1. 144 square inches
  2. 231 cubic inches
  3. 1,728 cubic inches Correct answer.
  4. 27 cubic inches

Explanation

A cubic foot measures 12 in x 12 in x 12 in, so its volume is 12 cubed, or 1,728 cubic inches. This conversion is used constantly when pipe or tank volumes must be restated in gallons, because 1 gallon equals 231 cubic inches.

Question 22Plumbing Math and Pipe Sizing Calculations

Approximately how many gallons of water does one cubic foot hold?

  1. 7.48 Correct answer.
  2. 8.34
  3. 62.4
  4. 3.79

Explanation

One cubic foot equals 1,728 cubic inches, and dividing by 231 cubic inches per gallon gives about 7.48 gallons. This factor is the standard bridge between pipe or tank volume in cubic feet and capacity in gallons.

Question 23Plumbing Math and Pipe Sizing Calculations

A vertical column of water one foot high produces what pressure at its base?

  1. 0.0361 psi
  2. 2.31 psi
  3. 0.433 psi Correct answer.
  4. 1.0 psi

Explanation

Water weighs 62.4 pounds per cubic foot, and spreading that weight over the 144 square inches of a one-square-foot base gives 62.4 divided by 144, or 0.433 psi per foot of height. This value is the basis for all static head calculations in water piping.

Question 24Plumbing Math and Pipe Sizing Calculations

A fixture outlet sits 10 feet above the supply main feeding it. Ignoring friction, what pressure is lost to the elevation change?

  1. 4.33 psi Correct answer.
  2. 23.1 psi
  3. 10.0 psi
  4. 2.31 psi

Explanation

Elevation change costs 0.433 psi for every foot of rise, so 10 feet times 0.433 psi per foot equals 4.33 psi of lost pressure. The result is subtracted from the available supply pressure when sizing the branch.

Question 25Plumbing Math and Pipe Sizing Calculations

A drain line is installed with a fall of 1/4 inch per foot. What is that grade expressed as a percent?

  1. 0.21%
  2. 2.08% Correct answer.
  3. 0.25%
  4. 4.17%

Explanation

Grade as a percent is the fall in inches divided by 12 inches of run times 100, so 0.25 divided by 12 times 100 equals about 2.08 percent. The same slope can therefore be described as 1/4 inch per foot or roughly 2 percent.

Question 26Plumbing Math and Pipe Sizing Calculations

One gallon of water weighs approximately:

  1. 3.79 pounds
  2. 62.4 pounds
  3. 7.48 pounds
  4. 8.34 pounds Correct answer.

Explanation

A gallon occupies 231 cubic inches, or about 0.1337 cubic foot, and 0.1337 times 62.4 pounds per cubic foot gives about 8.34 pounds. This weight is the standard factor for water heater recovery and heat calculations.

Question 27Plumbing Math and Pipe Sizing Calculations

Water moves through a pipe with a 2-inch inside diameter at 5 feet per second. What flow rate does this represent?

  1. 49 gpm Correct answer.
  2. 98 gpm
  3. 12 gpm
  4. 25 gpm

Explanation

The cross-sectional area is pi times the square of the 1-inch radius converted to feet, or about 0.0218 square foot. Multiplying by 5 feet per second gives 0.109 cubic foot per second, and multiplying by 448.8 gallons per minute per cubic foot per second gives about 49 gpm.

Question 28Plumbing Math and Pipe Sizing Calculations

A 100-foot length of pipe with a 2-inch inside diameter is completely filled with water. Approximately how many gallons does it hold?

  1. 32.6 gallons
  2. 65.3 gallons
  3. 16.3 gallons Correct answer.
  4. 8.2 gallons

Explanation

The pipe area is about 0.0218 square foot, so 100 feet of length holds 2.18 cubic feet. Multiplying by 7.48 gallons per cubic foot yields about 16.3 gallons.

Question 29Plumbing Math and Pipe Sizing Calculations

A horizontal drain branch runs 60 feet at a uniform slope of 1/4 inch per foot. What is the total fall over that run?

  1. 15 inches Correct answer.
  2. 24 inches
  3. 30 inches
  4. 7.5 inches

Explanation

Total fall equals the slope per foot multiplied by the length of the run, so 0.25 inch times 60 feet equals 15 inches. The same result can be checked as 1.25 feet of fall over 60 feet, which is the required 2 percent grade.

Question 30Plumbing Math and Pipe Sizing Calculations

A 5,000-gallon storage tank is filled at a steady rate of 20 gallons per minute. How long does filling take?

  1. 3 hours 20 minutes
  2. 5 hours 00 minutes
  3. 4 hours 10 minutes Correct answer.
  4. 2 hours 30 minutes

Explanation

Dividing 5,000 gallons by 20 gallons per minute gives 250 minutes. Converting 250 minutes to hours and minutes yields 4 hours and 10 minutes.

Question 31Plumbing Math and Pipe Sizing Calculations

A water heater has a 40,000 BTU/hr input and operates at 80 percent efficiency. What is its recovery rate when raising water 100 degrees F?

  1. 96 gallons per hour
  2. 38 gallons per hour Correct answer.
  3. 19 gallons per hour
  4. 48 gallons per hour

Explanation

Net input is 40,000 times 0.80, or 32,000 BTU/hr. Raising one gallon 100 degrees requires 8.33 pounds times 100 degrees, or 833 BTU, so 32,000 divided by 833 gives about 38 gallons per hour.

Question 32Plumbing Math and Pipe Sizing Calculations

A flow of 20 gallons per minute passes through a pipe with a 1-inch inside diameter. What is the velocity of the water?

  1. 2.1 feet per second
  2. 4.9 feet per second
  3. 8.2 feet per second Correct answer.
  4. 16.3 feet per second

Explanation

Convert the flow to 0.0446 cubic foot per second, then divide by the pipe area of about 0.00545 square foot. The quotient is about 8.2 feet per second, which is a reasonable velocity for a small cold-water branch.

Question 33Plumbing Math and Pipe Sizing Calculations

A piping run has a total equivalent length of 240 feet, and the selected pipe size loses 0.5 psi per 100 feet. What friction loss should be expected?

  1. 2.4 psi
  2. 4.8 psi
  3. 0.5 psi
  4. 1.2 psi Correct answer.

Explanation

Friction loss scales directly with equivalent length, so 240 feet divided by 100 feet gives 2.4 increments of 0.5 psi. Multiplying 2.4 by 0.5 psi produces 1.2 psi of loss.

Question 34Plumbing Math and Pipe Sizing Calculations

What is the cross-sectional area of the opening of a pipe with a 4-inch inside diameter?

  1. 25.13 square inches
  2. 50.27 square inches
  3. 4.00 square inches
  4. 12.57 square inches Correct answer.

Explanation

Area equals pi times the diameter squared divided by four, so 3.1416 times 16 divided by 4 equals about 12.57 square inches. This area is then used with velocity to find flow rate.

Question 35Plumbing Math and Pipe Sizing Calculations

At the same water velocity, a pipe with twice the inside diameter of another carries how many times as much flow?

  1. 2 times
  2. 16 times
  3. 4 times Correct answer.
  4. 8 times

Explanation

Flow equals area times velocity, and area varies with the square of the diameter. Doubling the diameter quadruples the area, so the flow at the same velocity becomes four times as great.

Question 36Plumbing Math and Pipe Sizing Calculations

A pressure gauge reads 50 psi. What height of water column does that pressure support?

  1. 21.7 feet
  2. 115.5 feet Correct answer.
  3. 216.5 feet
  4. 23.1 feet

Explanation

Each psi supports 2.31 feet of water, which is the reciprocal of 0.433 psi per foot. Multiplying 50 psi by 2.31 feet per psi gives about 115.5 feet of head.

Question 37Plumbing Math and Pipe Sizing Calculations

A water heater rated at 50,000 BTU/hr input is 76 percent efficient and must raise water 90 degrees F. What recovery rate does this produce?

  1. 51 gallons per hour Correct answer.
  2. 26 gallons per hour
  3. 60 gallons per hour
  4. 34 gallons per hour

Explanation

Net heat output is 50,000 times 0.76, or 38,000 BTU/hr. One gallon raised 90 degrees absorbs 8.33 times 90, or about 750 BTU, so 38,000 divided by 750 gives about 51 gallons per hour.

Question 38Plumbing Math and Pipe Sizing Calculations

A water service delivers 60 psi at the meter, where 5 psi is lost. The highest fixture is 25 feet above the meter and requires 8 psi to operate. What pressure remains for pipe friction?

  1. 32.2 psi
  2. 47.0 psi
  3. 41.2 psi
  4. 36.2 psi Correct answer.

Explanation

The 25-foot rise consumes 25 times 0.433, or about 10.8 psi of static pressure. Subtracting the meter loss, the elevation loss, and the fixture requirement from 60 psi leaves 60 minus 5 minus 10.8 minus 8, or about 36.2 psi for friction.

Question 39Plumbing Math and Pipe Sizing Calculations

A branch must carry 100 gallons per minute with a velocity no greater than 8 feet per second. What is the smallest standard pipe size that satisfies this limit?

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

Explanation

Convert 100 gpm to about 0.223 cubic foot per second, then divide by 8 feet per second to get the minimum area of 0.0279 square foot, or about 4.0 square inches. Solving for diameter gives about 2.26 inches, so the next standard size up, 2-1/2 inch, is required.

Question 40Plumbing Math and Pipe Sizing Calculations

A cylindrical tank is 6 feet in diameter and 8 feet tall. Approximately how many gallons does it hold when full?

  1. 846 gallons
  2. 2,256 gallons
  3. 1,692 gallons Correct answer.
  4. 1,354 gallons

Explanation

The volume of a cylinder is pi times radius squared times height, so 3.1416 times 9 times 8 equals about 226 cubic feet. Multiplying by 7.48 gallons per cubic foot gives roughly 1,692 gallons.

Question 41Drainage Systems and Drainage Piping

What is the minimum water seal depth required for a plumbing fixture trap?

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

Explanation

A fixture trap must hold a water seal of at least 2 inches and no more than 4 inches to block sewer gas while permitting wastewater flow. A seal shallower than 2 inches is easily broken, and one deeper than 4 inches can retard flow.

Question 42Drainage Systems and Drainage Piping

What is the minimum slope for a 3-inch horizontal drainage pipe?

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

Explanation

Horizontal drainage piping 3 inches and larger must slope at least 1/8 inch per foot so solids stay suspended and move toward the sewer. Smaller pipe requires 1/4 inch per foot because its shallower flow depth needs more velocity.

Question 43Drainage Systems and Drainage Piping

What drainage fixture unit (DFU) value is assigned to a water closet?

  1. 1 DFU
  2. 2 DFU
  3. 3 DFU Correct answer.
  4. 4 DFU

Explanation

In standard drainage fixture unit tables, a water closet is rated at 3 DFU, reflecting its discharge volume and frequency. Lavatories are typically 1 DFU, and bathtubs 2 DFU.

Question 44Drainage Systems and Drainage Piping

Which type of trap is prohibited in drainage systems?

  1. S-trap Correct answer.
  2. Drum trap with a cleanout
  3. P-trap
  4. Floor drain trap

Explanation

An S-trap has two bends in the same vertical plane and tends to siphon its own seal, so it is prohibited. Approved traps such as P-traps maintain a level seal and connect to a vent.

Question 45Drainage Systems and Drainage Piping

What is the primary purpose of limiting the length of a fixture trap arm?

  1. To reduce pipe support requirements
  2. To increase drain velocity
  3. To allow a smaller vent to be used
  4. To prevent trap seal self-siphonage Correct answer.

Explanation

A trap arm is the pipe between the trap and its vent. If it is too long, the trap can self-siphon before the vent can admit air, so the length is limited to protect the seal.

Question 46Drainage Systems and Drainage Piping

What is the function of a backwater valve in a drainage system?

  1. To stop sewage backup into the building Correct answer.
  2. To separate grease from wastewater
  3. To admit air into the drainage piping
  4. To reduce noise in the drain

Explanation

A backwater valve closes when flow reverses, preventing municipal sewer backup from entering the building drain. It is installed where the fixture level is below the nearest upstream manhole cover.

Question 47Drainage Systems and Drainage Piping

Where is a cleanout normally required at the bottom of a drainage stack?

  1. Inside each fixture trap
  2. At the base of the stack Correct answer.
  3. At each fixture water supply
  4. At the roof termination

Explanation

A cleanout is required at the base of a vertical drainage stack so the lower section and building drain can be rodded without removing fixtures. Cleanouts are also required at other changes in direction.

Question 48Drainage Systems and Drainage Piping

What is the minimum height a plumbing vent stack must extend above a flat roof surface?

  1. 6 inches Correct answer.
  2. 4 inches
  3. 2 inches
  4. 12 inches

Explanation

A vent stack must extend at least 6 inches above the roof surface to keep snow and debris from blocking it. Local codes may require more where snow accumulation is expected.

Question 49Drainage Systems and Drainage Piping

What is the maximum vertical fall permitted for a fixture trap arm between the trap and its vent?

  1. One foot
  2. Two pipe diameters
  3. One pipe diameter Correct answer.
  4. The trap seal depth

Explanation

The trap arm must slope toward the vent, but its total fall may not exceed one pipe diameter. Beyond that, the arm acts like a drain and can siphon the trap seal.

Question 50Drainage Systems and Drainage Piping

What is a wet vent?

  1. A vent that also drains a fixture Correct answer.
  2. A vent installed only on the exterior
  3. A vent that terminates below the roof
  4. A vent equipped with a backwater valve

Explanation

A wet vent carries air for one fixture while also draining another fixture upstream. It must be sized and arranged so it does not become a trap arm or clogged drain for the vented fixture.