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Question 1Plumbing Discipline

Under the Ontario Plumbing Code, what is the minimum permitted size of a building drain serving a single dwelling unit?

  1. 100 mm
  2. 75 mm Correct answer.
  3. 125 mm
  4. 50 mm

Explanation

A building drain for a single dwelling must be at least 75 mm in diameter so that it can carry the combined discharge of the fixtures without frequent blockage. Smaller sizes such as 50 mm are permitted only for specific branch or fixture drains, not the main building drain.

Question 2Plumbing Discipline

What is the standard slope required for a 100 mm horizontal building drain or branch?

  1. 1 in 400
  2. 1 in 50
  3. 1 in 100 Correct answer.
  4. 1 in 200

Explanation

Horizontal drainage pipe of 100 mm and smaller is installed at a fall of 1 in 50 to 1 in 100, and 1 in 100 is the commonly cited default that provides adequate scouring velocity. Flatter slopes risk solids settling, while steeper slopes can leave liquids behind.

Question 3Plumbing Discipline

A water closet is installed in a room. What is the minimum clear space required in front of the fixture, measured from the front of the bowl?

  1. 600 mm Correct answer.
  2. 380 mm
  3. 450 mm
  4. 750 mm

Explanation

Fixtures must have a clear space of at least 600 mm in front of the water closet, measured from the front of the bowl, to allow a person to stand and use the fixture. This clearance is separate from the side clearance between the fixture and adjacent walls.

Question 4Plumbing Discipline

Which device prevents sewer gas from entering a building through a fixture drain while allowing wastewater to pass?

  1. Air admittance valve
  2. P-trap Correct answer.
  3. Backwater valve
  4. Trap primer

Explanation

A P-trap holds a water seal that blocks sewer gas from entering the building while permitting wastewater to flow through. The depth of the water seal is specified by code to prevent both gas passage and self-siphonage.

Question 5Plumbing Discipline

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

  1. To equalize pressure and protect trap seals Correct answer.
  2. To drain condensate from fixtures
  3. To increase the flow velocity in the drain
  4. To provide a cleanout access point

Explanation

Venting equalizes air pressure on both sides of the trap seal so that siphonage and back-pressure do not pull the seal. Proper venting also allows air to enter the drain and keeps flow smooth.

Question 6Plumbing Discipline

Which material is typically prohibited for use as a water service pipe due to lead content?

  1. Type K copper
  2. Ductile iron
  3. Lead pipe Correct answer.
  4. Cross-linked polyethylene (PEX)

Explanation

Lead pipe is prohibited for potable water service because lead can leach into drinking water and cause health effects. Approved materials for water service include copper, PEX, and certain plastics and metals that meet standards.

Question 7Plumbing Discipline

What is the minimum air gap required for a fixture with an effective opening not more than 12 mm in diameter?

  1. 50 mm
  2. 100 mm
  3. 25 mm Correct answer.
  4. 12 mm

Explanation

The air gap must be at least twice the diameter of the effective opening of the outlet, with a minimum of 25 mm. For openings up to 12 mm, the 25 mm minimum governs.

Question 8Plumbing Discipline

Which fixture unit value is commonly assigned to a single private water closet in drainage sizing?

  1. 2 fixture units
  2. 1 fixture unit
  3. 4 fixture units Correct answer.
  4. 6 fixture units

Explanation

A private water closet is rated at 4 fixture units in the drainage fixture unit table, reflecting its discharge characteristics. This value is used to size the branch and building drain serving the fixture.

Question 9Plumbing Discipline

A 100 mm drain serving a single water closet must connect to a vertical stack. Which fitting is required at the base of the stack?

  1. Sanitary tee
  2. Long-sweep 90-degree bend Correct answer.
  3. Vent tee
  4. Double sanitary tee

Explanation

At the base of a soil stack where flow turns from vertical to horizontal, a long-sweep bend or a fitting with an equivalent radius is required to smooth the change of direction and reduce blockage. A sharp sanitary tee is not permitted for this change of direction.

Question 10Plumbing Discipline

A lavatory drain is 40 mm in size. What is the maximum distance the trap may be located from the fixture outlet?

  1. 1500 mm
  2. 1200 mm
  3. 900 mm Correct answer.
  4. 600 mm

Explanation

The developed length of the trap arm from the fixture outlet to the vent connection is limited, and for a 40 mm trap the maximum distance is 900 mm. Exceeding this limit risks self-siphonage of the trap seal.

Question 11Plumbing Discipline

What is the minimum size of a vent pipe serving a water closet branch in a drainage system?

  1. 40 mm Correct answer.
  2. 38 mm
  3. 50 mm
  4. 32 mm

Explanation

A vent serving a water closet must be at least 40 mm in diameter so it can handle the larger air demand when the fixture discharges. Smaller vents are permitted only for fixtures with smaller drains.

Question 12Plumbing Discipline

A building has a water service with a static pressure of 550 kPa. Which device should be installed to protect the plumbing system from excessive pressure?

  1. Backflow preventer
  2. Check valve
  3. Thermal expansion tank
  4. Pressure-reducing valve Correct answer.

Explanation

Where the static pressure exceeds the code limit (commonly 550 kPa), a pressure-reducing valve is required to bring pressure down to an acceptable level and protect fixtures and piping. A backflow preventer addresses contamination, not pressure.

Question 13Plumbing Discipline

Which of the following best describes the purpose of a backwater valve in a building drain?

  1. To vent the drainage system
  2. To separate greywater from blackwater
  3. To reduce water pressure
  4. To prevent sewage from backing up into the building Correct answer.

Explanation

A backwater valve is installed on a building drain where flooding of the public sewer could cause sewage to back up into the building. It allows flow out but closes against reverse flow.

Question 14Plumbing Discipline

A grease interceptor is required for a commercial kitchen. Which factor most directly determines the required size of the interceptor?

  1. The total flow rate from the fixtures served Correct answer.
  2. The number of employees
  3. The height of the building
  4. The diameter of the vent stack

Explanation

Grease interceptor capacity is sized based on the total flow rate from the fixtures it serves, such as sinks and dishwashers, so that grease has time to separate. Building height and vent size do not determine interceptor capacity.

Question 15Plumbing Discipline

What is the minimum depth of a water seal required for a trap under the plumbing code?

  1. 25 mm
  2. 75 mm
  3. 38 mm
  4. 50 mm Correct answer.

Explanation

A trap must maintain a water seal of at least 50 mm and not more than 100 mm. This depth resists evaporation and pressure fluctuations while avoiding excessive seal depth that could trap air.

Question 16Plumbing Discipline

A horizontal wet vent is used to vent a bathroom group. What condition must be met for this arrangement to be permitted?

  1. The water closet must be separately vented
  2. The trap arms must exceed 1500 mm
  3. The fixtures must be on the same floor and connected to a common drain Correct answer.
  4. The vent must be at least 100 mm in diameter

Explanation

A horizontal wet vent is permitted where the fixtures served are on the same floor and connected to a common horizontal drain that also serves as the vent. The drain must be sized to carry both the waste and the vented air.

Question 17Plumbing Discipline

Which of the following methods is acceptable for protecting a potable water supply from backflow at a hose bibb?

  1. A pressure-reducing valve
  2. A check valve
  3. A trap primer
  4. A vacuum breaker Correct answer.

Explanation

A hose bibb must be protected against backflow, typically by a vacuum breaker that opens to atmosphere when pressure drops, breaking any siphon. A simple check valve is not an approved backflow preventer for this application.

Question 18Plumbing Discipline

A storm drainage system must be kept separate from the sanitary drainage system. What is the primary reason for this separation?

  1. To allow smaller vent pipes
  2. To prevent storm water from overloading the sanitary sewer and treatment plant Correct answer.
  3. To simplify fixture installation
  4. To reduce the cost of piping

Explanation

Separating storm water from sanitary drainage prevents large storm flows from overwhelming sanitary sewers and treatment works, which can cause backups and bypasses. The separation also protects the treatment process from dilution.

Question 19Plumbing Discipline

A plumbing system serves a building with a water service pressure of 400 kPa and a large elevation difference between floors. Which consideration is most important in sizing the water distribution piping?

  1. The pressure loss from friction and elevation Correct answer.
  2. The slope of the horizontal drains
  3. The color of the pipe
  4. The number of cleanouts

Explanation

Water distribution sizing must account for both friction loss through the piping and the loss of pressure due to elevation gain, so that adequate pressure remains at the highest and farthest fixtures. Cleanouts and drain slope are unrelated to supply sizing.

Question 20Plumbing Discipline

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

  1. 150 mm
  2. 125 mm
  3. 75 mm
  4. 100 mm Correct answer.

Explanation

A building sewer serving a single dwelling must be at least 100 mm in diameter. This size provides adequate capacity for the combined discharge of the dwelling's fixtures.

Question 21Plumbing Discipline

A cleanout is required at the base of a soil stack. What is the maximum distance a cleanout may be located from the base of the stack?

  1. The cleanout may be on the next floor
  2. The cleanout may be up to 1500 mm away
  3. The cleanout must be at the base, within 300 mm of the fitting Correct answer.
  4. No specific limit

Explanation

A cleanout must be installed at the base of a soil or waste stack, close to the fitting, typically within 300 mm, so the lower section of the stack can be rodded. Placing it farther away leaves the base inaccessible.

Question 22Plumbing Discipline

A 100 mm horizontal drain carries a large fixture load and must connect to a vertical stack. Which fitting arrangement is acceptable for the horizontal-to-vertical connection?

  1. A vent tee
  2. A sanitary tee with the branch turned downward
  3. A double vent tee
  4. A wye fitting with a 45-degree bend Correct answer.

Explanation

When a horizontal drain enters a vertical stack, a wye fitting with a 45-degree bend or an equivalent long-turn fitting is used to direct flow smoothly downward. A sanitary tee with the branch turned downward is not permitted for this change of direction.

Question 23Plumbing Discipline

A multi-storey building requires a venting arrangement where a single vent serves two traps on different floors. Which condition must be satisfied for a common vent to be acceptable?

  1. The fixtures must be on the same floor
  2. The traps must be of different sizes
  3. The vent must be at least 100 mm
  4. The common vent must be sized for the total fixture units and the fixtures must be within the permitted distance Correct answer.

Explanation

A common vent may serve fixtures on different floors only where it is sized for the combined fixture units and each fixture is within the permitted distance from the vent. Otherwise, back-pressure or siphonage can occur.

Question 24Plumbing Discipline

A building's water service is supplied from a public main at 350 kPa. The highest fixture is 20 m above the service connection. What is the approximate static pressure remaining at that fixture, ignoring friction?

  1. Approximately 200 kPa
  2. Approximately 550 kPa
  3. Approximately 150 kPa Correct answer.
  4. Approximately 350 kPa

Explanation

Static pressure drops by about 9.8 kPa per metre of elevation, so 20 m of rise reduces pressure by roughly 196 kPa. Subtracting that from 350 kPa leaves approximately 150 kPa at the highest fixture, before friction losses are considered.

Question 25Plumbing Discipline

A drainage system has a fixture with a trap arm that exceeds the permitted length. Which problem is most likely to occur?

  1. The fixture will drain too slowly
  2. The water pressure will increase
  3. The trap seal may be lost through self-siphonage Correct answer.
  4. The vent will become blocked with grease

Explanation

An excessively long trap arm allows the momentum of the discharging waste to create a partial vacuum that can siphon the trap seal. The remedy is to shorten the trap arm or add a vent closer to the fixture.

Question 26Plumbing Discipline

A drainage stack in a high-rise building carries soil from water closets and must resist positive pressure at its base and negative pressure near the top. Which term describes the pressure fluctuation that a properly sized vent must control?

  1. Thermal expansion of the stack riser
  2. Hydraulic jump at the stack-to-drain transition
  3. Surcharge from the building sewer during peak flow
  4. Trap seal loss caused by pneumatic pressure differences Correct answer.

Explanation

Venting exists primarily to equalise pneumatic pressure across the trap seal so that neither positive nor negative pressure in the drainage system can siphon or bubble the seal. Surcharge and hydraulic jump describe flow conditions in drains, not the pressure control function of venting.

Question 27Plumbing Discipline

Which condition determines whether a plumbing fixture must be provided with a trap?

  1. Only fixtures that receive human waste require a trap
  2. Only fixtures installed above the lowest floor require a trap
  3. Only fixtures connected to a combined sewer require a trap
  4. Every fixture that discharges to the drainage system must have a trap Correct answer.

Explanation

The general rule is that each fixture discharging into the drainage system must be trapped, so that sewer gas cannot enter the building through the fixture. The requirement does not depend on waste type, floor level, or sewer type.

Question 28Plumbing Discipline

A fixture drain must be protected from backflow of sewage from the building drain. Which arrangement provides the required protection for a fixture set below the level of the adjoining street or public sewer?

  1. A trap primer connected to the fixture trap
  2. A backwater valve installed on the fixture branch or the building drain Correct answer.
  3. A vent pipe extended above the roof
  4. A cleanout installed at the fixture outlet

Explanation

Fixtures that cannot drain by gravity to the public sewer because they sit below flood level of the sewer need a backwater valve to stop sewage from reversing into the building. Vents, cleanouts, and trap primers serve other functions and cannot stop a reverse flow.

Question 29Plumbing Discipline

In a drainage system, what is the primary function of a trap arm?

  1. To carry waste from the trap to the vent or stack while protecting the trap seal Correct answer.
  2. To support the weight of the fixture above the floor
  3. To provide access for rodding the branch drain
  4. To reduce the velocity of discharge entering the stack

Explanation

The trap arm is the pipe between the trap weir and the vent or stack, and its length and slope are limited so that the trap seal is not lost through self-siphonage. It is not a support element, an access point, or a velocity-control device.

Question 30Plumbing Discipline

Which material is commonly used for underground sanitary drainage pipe where resistance to sulphide attack and joint tightness are priorities?

  1. Cast iron soil pipe with compression gaskets Correct answer.
  2. Copper tube with soldered joints
  3. Aluminium pipe with mechanical couplings
  4. Galvanised steel pipe with threaded joints

Explanation

Cast iron soil pipe with rubber compression gaskets is widely used underground because the joints remain tight under ground movement and the material tolerates the aggressive conditions found in sanitary drainage. Steel, copper, and aluminium are not the standard choice for underground soil drainage.

Question 31Plumbing Discipline

A water closet is installed in a small room and the fixture must be set out to allow proper use and cleaning. Which clearance is normally required in front of the water closet?

  1. At least 150 mm from the front of the bowl to any wall or obstruction
  2. At least 600 mm from the front of the bowl to any wall or obstruction Correct answer.
  3. At least 300 mm from the front of the bowl to any wall or obstruction
  4. At least 900 mm from the front of the bowl to any wall or obstruction

Explanation

A clearance of about 600 mm in front of the water closet is the usual minimum that allows a person to use the fixture and permits cleaning. Smaller clearances do not allow proper use, and 900 mm is a generous dimension rather than the minimum.

Question 32Plumbing Discipline

A plumbing vent terminates through a roof. Which requirement applies to the vent terminal?

  1. It must extend above the roof and be located away from windows and air intakes Correct answer.
  2. It must discharge into the stormwater downpipe
  3. It must terminate below the roof surface to avoid frost
  4. It must be fitted with a rain cap that seals the vent

Explanation

Vent terminals must extend above the roof surface and be positioned so that sewer gas does not enter windows, doors, or air intakes. Terminating below the roof, sealing the vent, or connecting to a downpipe would defeat the vent's purpose or create a hazard.

Question 33Plumbing Discipline

Which device is installed on a water heater to prevent the tank from exceeding a safe temperature and pressure?

  1. An expansion control valve on the drain line
  2. A check valve on the cold inlet
  3. A temperature and pressure relief valve Correct answer.
  4. A vacuum relief valve

Explanation

A temperature and pressure relief valve opens when either the temperature or the pressure in the storage tank reaches its set limit, protecting the tank from rupture. The other devices control flow direction, vacuum, or expansion but do not relieve both over-temperature and over-pressure.

Question 34Plumbing Discipline

A 32 mm copper water service runs 25 m to a building and supplies a fixture requiring a flow of 0.3 L/s. Which factor most directly reduces the pressure available at the fixture?

  1. The depth of the service trench
  2. Friction loss through the pipe and fittings Correct answer.
  3. The static head of the water main
  4. The colour coding of the pipe

Explanation

Pressure at the fixture equals the available supply pressure minus losses, and the dominant loss is friction through the pipe, fittings, and valves, which grows with flow rate and pipe length. Trench depth and pipe colour do not affect hydraulic performance, and main static head is the source pressure rather than a loss.

Question 35Plumbing Discipline

A horizontal drain of 80 mm diameter must change direction by 90 degrees in the direction of flow. Which fitting is appropriate at this change?

  1. A short-radius bend
  2. A long-radius bend Correct answer.
  3. A reducing coupling
  4. A sanitary tee

Explanation

Where a horizontal drain changes direction, a long-radius bend keeps the flow smooth and reduces the risk of blockage and turbulence. A short-radius bend or a sanitary tee creates a sharp change that promotes solids build-up, and a reducing coupling changes size rather than direction.

Question 36Plumbing Discipline

A building has a 150 mm building drain laid at a slope of 1 in 60 over a 30 m run. What is the approximate fall over that length?

  1. 250 mm
  2. 1000 mm
  3. 500 mm Correct answer.
  4. 1800 mm

Explanation

Fall equals length divided by the slope ratio, so 30 000 mm divided by 60 gives 500 mm. The other values correspond to different slopes and would not satisfy the stated gradient.

Question 37Plumbing Discipline

A pump delivers water to a storage tank at the top of a building. Which arrangement prevents water from the tank flowing back into the potable supply when the pump stops?

  1. A drain cock at the lowest point of the line
  2. A pressure gauge on the pump discharge
  3. A check valve and an air gap at the tank inlet Correct answer.
  4. A gate valve on the discharge line

Explanation

A check valve stops reverse flow when the pump stops, and an air gap at the tank inlet provides a physical separation that prevents back-siphonage even if the check valve leaks. A gate valve, gauge, or drain cock does not provide backflow protection.

Question 38Plumbing Discipline

A stack serving a group of fixtures receives a branch from a water closet. Which requirement applies to the connection of a water closet branch to a vertical stack?

  1. It may be made with a cross fitting to serve two branches
  2. It must be made below the lowest fixture on the stack
  3. It must be made with a reducing tee to control velocity
  4. It must be made with a fitting that directs flow in the direction of the stack flow Correct answer.

Explanation

Branches entering a vertical stack must use fittings that turn the flow downward in the direction of stack flow, which is why sanitary tees and similar fittings are used. Cross fittings are not permitted for this purpose, and the connection is not restricted to below the lowest fixture.

Question 39Plumbing Discipline

A trap serving a seldom-used floor drain in a plant room is at risk of losing its seal through evaporation. Which measure maintains the seal?

  1. Fitting a vent on the downstream side of the trap
  2. Replacing the trap with a running trap
  3. Installing a trap primer that discharges water into the trap Correct answer.
  4. Increasing the depth of the trap seal beyond the code minimum

Explanation

Evaporation is best countered by regularly replenishing water in the trap, which is what a trap primer does. Deepening the seal only delays the problem, a running trap does not prevent evaporation, and a downstream vent does not add water.

Question 40Plumbing Discipline

A grease interceptor serving a commercial kitchen is being sized. Which factor most directly determines its required capacity?

  1. The diameter of the kitchen waste pipe
  2. The rate of flow from the fixtures discharging to it and the retention time required Correct answer.
  3. The temperature of the cold water supply
  4. The number of floors in the building

Explanation

Interceptor sizing depends on the flow rate entering it and the retention time needed for fats, oils, and grease to separate and float. Pipe diameter, building height, and supply water temperature do not determine the separation capacity required.

Question 41Plumbing Discipline

A water supply pipe passes through a concrete slab in a building where movement is expected. Which detail protects the pipe?

  1. Rigid embedding of the pipe directly in the concrete
  2. A sleeve that allows movement and separates the pipe from the concrete Correct answer.
  3. A reduction in pipe diameter at the penetration
  4. A cap fitted over the pipe end

Explanation

A sleeve isolates the pipe from the concrete and allows differential movement, preventing abrasion, crushing, and stress at the penetration. Embedding the pipe rigidly or altering the diameter at the penetration creates stress concentrations and is not acceptable.

Question 42Plumbing Discipline

A drainage system requires a vent that also serves as a drain for rainwater entering the vent terminal. Which arrangement is used?

  1. A vent pipe terminated with a sealed cap
  2. A vent connected to the stormwater system only
  3. A vent stack with a drain at its base connected to the drainage system Correct answer.
  4. A vent that discharges into a roof gutter

Explanation

Where a vent may receive rainwater, a drain at the base of the vent stack carries that water into the drainage system rather than allowing it to accumulate. Sealing the vent defeats its purpose, and discharging to a gutter or stormwater line is not the drainage-system arrangement.

Question 43Plumbing Discipline

A multi-storey building uses a single vent stack to vent branches on several floors. Which condition must be satisfied for this arrangement to work?

  1. The vent stack must be sized for the total fixture load it serves Correct answer.
  2. The vent stack must be connected only at the top floor
  3. The vent stack must be fitted with a relief valve
  4. The vent stack must be smaller than the soil stack it serves

Explanation

A vent stack serving multiple floors must be sized for the total drainage load connected to it so it can equalise pressure throughout. Making it smaller than the soil stack, connecting only at the top, or fitting a relief valve would not provide adequate venting.

Question 44Plumbing Discipline

A plumbing system is being designed for a building where the water main pressure is 500 kPa and the highest fixture is 25 m above the connection. Which conclusion is correct?

  1. Static pressure at the highest fixture is about 50 kPa before friction losses
  2. Static pressure at the highest fixture is about 500 kPa before friction losses
  3. Static pressure at the highest fixture is about 745 kPa before friction losses
  4. Static pressure at the highest fixture is about 255 kPa before friction losses Correct answer.

Explanation

Each metre of elevation reduces pressure by about 9.8 kPa, so 25 m reduces pressure by about 245 kPa, leaving about 255 kPa before friction losses. The other figures either ignore elevation or add it in the wrong direction.

Question 45Plumbing Discipline

A drainage stack in a tall building must be offset horizontally to avoid a structural beam. Which measure is required at the offset to maintain venting performance?

  1. A relief vent or yoke vent is provided at the offset Correct answer.
  2. The offset is left unvented because it is above the lowest branch
  3. The offset is converted to a stormwater connection
  4. The offset is made with a short-radius bend only

Explanation

Offsets in a drainage stack create a section where pressure can build up, so a relief or yoke vent is provided to equalise pressure and protect trap seals. A short-radius bend alone, an unvented offset, or a stormwater connection would not address the pressure problem.

Question 46Plumbing Discipline

A building has a basement fixture that cannot drain by gravity to the public sewer. Which combination correctly describes the required protection and disposal arrangement?

  1. A cleanout at the fixture and a direct connection to the stormwater system
  2. A trap primer on the fixture and a soakaway in the basement
  3. A backwater valve on the fixture branch and a lifting pump discharging to the building drain Correct answer.
  4. A vent on the fixture branch and a floor drain discharging to the sewer

Explanation

A fixture below the sewer flood level needs a backwater valve to prevent reverse flow and a means of lifting its discharge to the building drain, typically a pump. Venting, cleanouts, trap primers, stormwater connections, or soakaways do not provide this protection and disposal.

Question 47Plumbing Discipline

A vent serving a fixture trap is connected to a horizontal drain. Which condition must be met for the vent connection to function correctly?

  1. The vent must connect above the crown of the trap arm and rise vertically to the vent stack Correct answer.
  2. The vent must connect below the trap weir to drain condensation
  3. The vent must be smaller than the trap arm it serves
  4. The vent must be horizontal for its entire length

Explanation

A vent must connect above the crown of the trap arm so that it remains clear of water and can admit air, and it must rise to the vent stack. Connecting below the weir, running horizontally throughout, or reducing the size would impair venting.

Question 48Plumbing Discipline

A large building has a combination waste and vent system where the drain also serves as a vent. Which design condition is essential for this system to operate correctly?

  1. The drain must be oversized relative to the fixture load so that it flows partly full Correct answer.
  2. The drain must be fitted with a backwater valve at each fixture
  3. The drain must be installed with a slope steeper than normal
  4. The drain must be connected to the stormwater system

Explanation

In a combination waste and vent system the drain carries both waste and air, so it must be oversized to run partly full and leave an air path above the flow. Steeper slopes, backwater valves at fixtures, or stormwater connections do not achieve this.

Question 49Plumbing Discipline

A water supply system has a pressure-reducing valve set at 350 kPa and a fixture requiring a minimum of 100 kPa. The pipe run has friction losses of 180 kPa. Which conclusion is correct?

  1. The fixture supply cannot be assessed without knowing the pipe colour
  2. The fixture will be adequately supplied because 350 minus 180 leaves 170 kPa Correct answer.
  3. The fixture will be starved because 350 minus 180 leaves 170 kPa above the minimum
  4. The fixture will be starved because 350 minus 180 leaves 170 kPa below the minimum

Explanation

Available pressure at the fixture is the set pressure minus friction losses, giving 170 kPa, which exceeds the 100 kPa minimum, so the fixture is adequately supplied. The options claiming starvation misread the comparison, and pipe colour is irrelevant.

Question 50Plumbing Discipline

A plumbing installation includes a fixture with a trap arm longer than the permitted maximum. Which problem is most likely to result?

  1. The trap seal may be lost through self-siphonage Correct answer.
  2. The trap will freeze in cold weather
  3. The vent will fill with water and block
  4. The fixture will discharge more slowly than designed

Explanation

An excessively long trap arm allows a slug of waste to develop enough momentum to siphon the trap seal when it discharges into the stack. Slower discharge, a blocked vent, and freezing are not the direct consequence of excessive trap arm length.