CSLB Trade — Plumbing (C-36) — All Questions
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105 questions
In a wet-vented bathroom group, a wet-vent section carrying 4 DFU must be at least what size?
- a.2 inch✓
- b.1-1/4 inch
- c.3 inch
- d.1-1/2 inch
For wet venting, a section carrying 3 to 4 DFU must be at least 2 inches. Sections carrying 1 to 2 DFU may be 1-1/2 inch. A 1-1/4 inch pipe is below the wet-vent minimum, and 3 inches is larger than required for 4 DFU.2022 California Plumbing Code (CPC) §908.0
An island sink, with no wall to run a vent up, is commonly vented using a:
- a.Relief vent only
- b.Island (loop) vent✓
- c.Common vent
- d.Circuit vent
An island sink is typically served by an island or loop vent, which rises as high as possible under the countertop, loops back down, and connects to the vent system to allow venting where no wall is available. A circuit vent serves a battery of fixtures, a relief vent supplements a stack, and a common vent joins only two fixtures at the same level.
A common vent may serve how many fixtures connected at the same level?
- a.4
- b.2✓
- c.8
- d.3
A common vent serves two fixtures that connect to the drainage system at the same level through a single vent. Three or four fixtures exceed the common-vent limit and need another venting method, and eight is the maximum for a circuit vent, not a common vent.2022 California Plumbing Code (CPC) §905.6
A fixture is 5 feet from its vent, but the trap arm is 1-1/2 inch, which allows only 3 feet 6 inches. The correct fix is to:
- a.Install a deeper-seal trap
- b.Add a cleanout at the trap
- c.Increase the trap arm to 2 inch, which allows 5 feet✓
- d.Slope the arm more steeply
Increasing the trap arm to 2 inch raises the allowable developed length to 5 feet, satisfying the trap-to-vent distance. Adding a cleanout or a deeper trap does not change the maximum trap-arm length. Increasing the slope beyond limits would drop the vent below the trap weir and promote siphonage.2022 California Plumbing Code (CPC) §1002.2
The minimum slope for a 2-1/2 inch horizontal drainage pipe is:
- a.1/8 inch per foot
- b.1/2 inch per foot
- c.1/4 inch per foot✓
- d.1/16 inch per foot
Pipe 2-1/2 inches and smaller requires a minimum slope of 1/4 inch per foot. The 1/8 inch per foot minimum applies only to pipe 3 inches and larger, so it is too flat here. The 1/16 inch value is below any code minimum, and 1/2 inch exceeds the required minimum.2022 California Plumbing Code (CPC) §708.1
The size of a building drain or sewer:
- a.May increase then reduce
- b.May be reduced after a fixture branch
- c.Shall not decrease in size in the direction of flow✓
- d.May be reduced after each cleanout
A drain or sewer must not decrease in size in the direction of flow, because a reduction creates a choke point where solids collect and clog. It may stay the same or increase downstream. Reducing after a cleanout or a branch still violates the no-reduction rule.
A vent that terminates through a side wall must be located at least how far from a property line and from openings such as windows?
- a.10 feet✓
- b.5 feet
- c.3 feet
- d.1 foot
A sidewall vent termination must be at least 10 feet from the property line and at least 10 feet horizontally from any openable opening (unless 3 feet above it), and be protected against birds and rodents. Distances of 3, 5, or 1 foot are less than the required separation and could let sewer gas enter openings.2022 California Plumbing Code (CPC) §906.2
A trap primer is installed on a floor drain trap in order to:
- a.Increase the drain slope
- b.Replenish water and maintain the trap seal✓
- c.Serve as the vent
- d.Clean the trap automatically
A trap primer periodically adds water to a seldom-used trap, such as a floor drain, to replenish the seal that would otherwise evaporate and let sewer gas escape. It does not clean the trap, act as a vent, or change the pipe slope. Maintaining the seal is its sole purpose.
A residential clothes washer standpipe is assigned what DFU value and minimum trap size?
- a.2 DFU, 3 inch
- b.3 DFU, 2 inch
- c.2 DFU, 2 inch✓
- d.1 DFU, 1-1/2 inch
A domestic clothes washer standpipe is assigned 2 DFU and requires a minimum 2 inch trap and standpipe to handle its rapid pump-out discharge. A 1-1/2 inch trap is too small for a washer, and neither 1 DFU nor 3 inch matches the code value for a residential washer.2022 California Plumbing Code (CPC) §702.0 (Table 702.1)
A horizontal branch serves two water closets (3 DFU each), two lavatories (1 DFU each), and two showers (2 DFU each). What is the minimum branch size?
- a.4 inch
- b.2 inch
- c.3 inch✓
- d.1-1/2 inch
The load is (2 x 3) + (2 x 1) + (2 x 2) = 6 + 2 + 4 = 12 DFU. A 3 inch branch carries up to 20 DFU and allows a maximum of two water closets, so it fits both the 12 DFU load and the two closets. A 2 inch branch (6 DFU) and 1-1/2 inch branch (3 DFU) are undersized, and a 4 inch branch is larger than needed here.2022 California Plumbing Code (CPC) §703.0 (Table 703.1)
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A plumber terminates a vent pipe through a residential roof that is used only for weather protection. What is the minimum height the vent must extend above the roof surface?
- a.At least 3 inches above the roof
- b.At least 12 inches above the roof
- c.At least 6 inches (152 mm) above the roof✓
- d.Flush with the roof surface
The CPC requires a vent terminal to extend not less than 6 inches above the roof. A terminal set too low can be blocked by roofing material, snow, or debris, defeating the vent. Some jurisdictions require more height for snow load, but 6 inches is the code minimum.2022 California Plumbing Code (CPC) §906.1
A vent penetrates a roof deck that is also used as a sun deck or walking surface. How high must the vent terminal extend above that roof?
- a.36 inches
- b.At least 7 feet (2134 mm) above the roof✓
- c.6 inches
- d.3 feet
When a roof is used for purposes other than weather protection (such as a deck or garden), a vent must terminate at least 7 feet above the roof surface. This keeps sewer gases well above the breathing zone of people using the roof.2022 California Plumbing Code (CPC) §906.1
A vent terminal is located 8 feet horizontally from an openable window. Under the CPC it must either terminate at least 10 feet away or…
- a.at least 2 feet above the window
- b.at least 3 feet (914 mm) above the top of the window✓
- c.at least 12 inches above the window
- d.at least 6 inches above the window
A vent terminal within 10 feet horizontally of a door, openable window, or air intake must extend at least 3 feet above that opening. At 8 feet away the plumber is inside the 10-foot zone, so the 3-foot rise applies to keep sewer gas from entering the building.2022 California Plumbing Code (CPC) §906.2
An air admittance valve (AAV) serving an individual fixture must be installed a minimum distance above the horizontal branch drain it serves. What is that minimum?
- a.1 inch above the flood-level rim
- b.At least 4 inches (102 mm) above the horizontal branch drain✓
- c.At the same level as the trap weir
- d.2 inches above the fixture drain
An AAV must be installed at least 4 inches above the horizontal branch drain it serves and above the trap weir of the fixture. This keeps the valve out of the wetted flow path so it can admit air freely when negative pressure occurs. AAVs must also remain accessible for replacement.2022 California Plumbing Code (CPC) §918.0
Where are air admittance valves (AAVs) prohibited from being installed?
- a.In a location where they could be exposed to a supply or return air plenum✓
- b.Under a lavatory in a vanity cabinet
- c.In an accessible attic space
- d.Within a wall cavity that has a ventilation grille
AAVs must not be installed in a supply or return air plenum, because a valve failure could draw sewer gas into the building's air distribution. They must be located in a ventilated, accessible space and installed above the fixtures they serve. Attics and vanity cabinets are commonly acceptable when accessible.2022 California Plumbing Code (CPC) §918.0
What term describes a vent that connects to the drain of a single fixture and extends independently to the outside air or to another vent?
- a.Circuit vent
- b.Wet vent
- c.Individual (back) vent✓
- d.Relief vent
An individual vent (sometimes called a back vent) serves the trap of one fixture and rises independently to open air or ties into another vent above the flood-level rim. It is the most basic vent type and directly protects a single trap seal from siphonage and back-pressure.2022 California Plumbing Code (CPC) §901.0
Two fixtures connected at the same level to a vertical drain and served by a single shared vent are using which venting method?
- a.Island vent
- b.Wet vent
- c.Yoke vent
- d.Common vent✓
A common vent serves two fixtures that connect at the same level to a shared vertical drain and are vented by one vent. The connecting drain and the vent must be sized for the combined fixture load. This is efficient for back-to-back fixtures such as two lavatories.
A horizontal wet-vent system under the CPC is limited to serving fixtures within…
- a.up to eight fixtures of any type
- b.one or two bathroom groups on the same floor level✓
- c.a kitchen and laundry group
- d.any group of fixtures on one floor
Wet venting under the CPC is limited to the fixtures of one or two bathroom groups located on the same floor level. The drain of an upstream fixture serves as the vent for a downstream fixture, so the arrangement is restricted to controlled bathroom-group layouts. Kitchen and laundry fixtures are not part of a wet-vented bathroom group.2022 California Plumbing Code (CPC) §908.0
In a bathroom-group wet vent, where is the dry vent connection typically made?
- a.At the most downstream fixture
- b.At the water closet only
- c.At the bathtub trap arm exclusively
- d.At the most upstream fixture drain, so the vent draws through the wet-vented section✓
The dry vent for a wet-vented bathroom group is connected at the drain of the most upstream fixture (commonly a lavatory). Air is then drawn through the wet-vented drain to protect the downstream fixture traps. The water closet is usually the most downstream fixture on the wet-vented branch.2022 California Plumbing Code (CPC) §908.0
A circuit vent serving a battery of floor-mounted fixtures on a horizontal branch may serve a maximum of how many fixtures?
- a.6
- b.8✓
- c.12
- d.10
A circuit vent may serve a battery of up to 8 fixtures connected to a horizontal branch drain. A single vent rises between the last two fixtures to serve the whole battery, and a relief vent may be required where fixtures discharge above. This method suits banks of floor-mounted water closets or urinals.2022 California Plumbing Code (CPC) §911.0
A kitchen island sink with no adjacent wall for a conventional vent is best served by which venting arrangement?
- a.A relief vent only
- b.An island fixture (loop) vent✓
- c.A common vent
- d.An air-break standpipe
An island fixture vent, often called a loop vent, rises from the fixture drain, loops up as high as possible under the countertop, then returns down and back to the vent system. It is used where the sink is not against a wall, such as a kitchen island. A foot (relief) vent and accessible cleanouts are typically required.2022 California Plumbing Code (CPC) §909.0
What is the minimum diameter permitted for a vent pipe, regardless of the fixture it serves?
- a.1/2 inch
- b.1-1/4 inches (32 mm)✓
- c.3/4 inch
- d.1 inch
No vent pipe may be smaller than 1-1/4 inches in diameter. In addition, a vent must generally be at least one-half the diameter of the drain it serves. Undersized vents are prone to clogging and cannot relieve pressure fast enough to protect trap seals.
A tall drainage stack with five or more branch intervals generally requires what to protect trap seals from pressure changes?
- a.A larger building trap
- b.A vent stack (main vent) installed adjacent to the soil/waste stack✓
- c.A backwater valve at each branch
- d.An additional cleanout only
A vent stack, or main vent, runs parallel to a tall soil or waste stack and is cross-connected with relief vents at intervals. It equalizes air pressure so that the surge of water down the stack does not siphon or blow out trap seals. Vent stacks are typically required once a stack has several branch intervals.2022 California Plumbing Code (CPC) §904.0
In a cold climate subject to frost closure, a vent through the roof must be enlarged to a minimum of 3 inches. Where must that increase in size be made?
- a.Only at the roof line itself
- b.At least 12 inches (305 mm) inside the building before the vent passes through the roof✓
- c.24 inches above the roof
- d.6 inches before passing through the roof
In frost-closure climates, a vent terminal must be at least 3 inches in diameter to resist closing off from frost. The increase from the smaller vent size must be made at least 12 inches inside the building before the pipe penetrates the roof. This keeps the enlarged, warmer section below the freezing zone.2022 California Plumbing Code (CPC) §906.0
A sewage ejector receiving the discharge of a water closet must have a discharge pipe of not less than what diameter and be able to pass a 2-inch solid?
- a.4 inches
- b.1-1/4 inches
- c.1-1/2 inches
- d.2 inches (51 mm)✓
A pump or ejector handling water-closet discharge must have a discharge pipe of at least 2 inches and be capable of passing a 2-inch spherical solid. This prevents clogging by the solids typical of sanitary sewage. Smaller effluent-only pumps are permitted only where they handle liquid waste without solids.2022 California Plumbing Code (CPC) §710.0
A sump or receiving tank that collects sewage from fixtures located below the sewer level must be…
- a.left unvented if the pump is sealed
- b.open to the room for inspection
- c.vented only to the interior of the building
- d.gastight (sealed) and provided with a vent to the outside air✓
A sump that receives sewage must be gastight and vented to the outside air to control sewer gas and equalize pressure as the pump cycles. An open or interior-vented sump would release odors and gases into the building. Clear-water sumps that handle no sewage may have different requirements.2022 California Plumbing Code (CPC) §710.0
Fixtures with flood-level rims located below the elevation of the next upstream manhole cover must be protected from sewer backflow by…
- a.An air-admittance valve
- b.A deeper trap seal
- c.An approved backwater valve✓
- d.A larger vent
Fixtures whose flood-level rims are below the next upstream manhole cover can flood when the public sewer surcharges, so they must discharge through an approved backwater valve. Fixtures above that elevation must not drain through the backwater valve, so they still drain by gravity if the valve closes. This protects low fixtures without impeding normal flow from higher ones.2022 California Plumbing Code (CPC) §710.1
An installed backwater valve must be…
- a.accessible for service and maintenance✓
- b.located inside the building trap
- c.installed only in a vertical pipe
- d.buried and permanently sealed
A backwater valve must be installed so it remains accessible for inspection, cleaning, and repair, typically in a valve box or cleanout enclosure at grade. A buried or sealed valve cannot be serviced and will fail without warning. Accessibility is a core code requirement for any backwater device.2022 California Plumbing Code (CPC) §710.1
Under the CPC, rainwater (storm) drainage and sanitary sewage generally must…
- a.combine only if the pipe is upsized
- b.be kept in separate piping systems and not combined unless a combined public sewer is approved✓
- c.share the same building drain
- d.combine at the building trap
Storm and sanitary drainage must be kept separate; rainwater must not discharge into a sanitary sewer, and sanitary waste must not enter a storm drain, unless the jurisdiction has an approved combined sewer. Combining the systems can overload the sanitary sewer during storms and cause backups. Where a combined public sewer exists, connection rules are set by the local authority.2022 California Plumbing Code (CPC) §1101.0
The air gap for an indirect waste pipe discharging into a receptor must be at least…
- a.1/2 inch
- b.3 inches minimum
- c.twice the effective opening (diameter) of the indirect waste pipe, and not less than 1 inch✓
- d.equal to the pipe diameter
An indirect waste air gap must be at least twice the effective opening of the drain pipe, measured vertically, and never less than 1 inch. This physical separation prevents sewage from backing up into the equipment through the indirect drain. It is the same principle used for potable-water air gaps.2022 California Plumbing Code (CPC) §801.2
Food-handling equipment such as a commercial food-prep sink or an ice machine must discharge to the drainage system by means of…
- a.An air-admittance valve
- b.A direct hard connection to the sewer
- c.A trap primer only
- d.An indirect waste with an air gap to a floor sink or receptor✓
Equipment used to store, prepare, or serve food must drain indirectly through an air gap into a floor sink or other approved receptor. The air gap prevents sewage from ever backing up into food-contact equipment. A direct connection to the sewer is prohibited for such equipment.2022 California Plumbing Code (CPC) §801.0
A domestic dishwasher discharge, before it connects to the drainage system, must be protected against backflow by…
- a.a backwater valve
- b.a deep-seal trap
- c.an air gap (or an approved high loop where permitted) in the drain line✓
- d.a check valve at the pump
A dishwasher drain must be protected by an air-gap fitting, or by a high loop where the local code allows, so waste cannot siphon back into the machine. The air gap is the most reliable method and is required by many jurisdictions. This protects the dishwasher and the food washed in it from contamination.2022 California Plumbing Code (CPC) §807.0
Which establishment is most likely required to install a grease interceptor or grease trap?
- a.A retail clothing store restroom
- b.A restaurant with commercial food preparation producing fats, oils, and grease (FOG)✓
- c.A single-family residential kitchen
- d.An office break room with only a coffee maker
Grease interceptors are required where fats, oils, and grease are generated in quantity, such as restaurants and commercial kitchens. FOG cools and hardens in the sewer, causing blockages and backups if not intercepted. Single-family homes and low-grease uses are generally exempt.2022 California Plumbing Code (CPC) §1014.0
A gravity grease interceptor (the large in-ground type) commonly has a minimum liquid capacity of…
- a.100 gallons
- b.500 gallons
- c.750 gallons (2839 L)✓
- d.50 gallons
Gravity grease interceptors are large in-ground tanks with a typical minimum liquid capacity of 750 gallons, sized upward based on the drainage load (DFU or seating). Their large volume and long retention time let grease float and settle before the effluent leaves. Small hydromechanical units serve lower-flow applications instead.2022 California Plumbing Code (CPC) §1014.0
The size of a hydromechanical grease interceptor is primarily selected based on…
- a.the color of the discharge
- b.the number of restrooms in the building
- c.the length of the drain line only
- d.the flow rate (GPM) of the fixtures it serves and its rated grease retention capacity✓
A hydromechanical (point-of-use) grease interceptor is selected by the flow rate in GPM it must handle and its rated grease capacity in pounds. A flow-control fitting limits flow to the rated GPM so grease can separate. Undersizing lets grease pass straight through to the sewer.2022 California Plumbing Code (CPC) §1014.0
The required size of vertical and horizontal storm (rainwater) piping is determined from code tables based on the projected roof area and…
- a.the sanitary DFU count
- b.the local rainfall rate in inches per hour✓
- c.the building trap size
- d.the number of floor drains
Storm drain and leader sizing is based on the horizontally projected roof area served and the local design rainfall rate in inches per hour. A higher rainfall rate or larger roof area requires larger pipe. Local jurisdictions publish the design storm intensity used for these calculations.2022 California Plumbing Code (CPC) §1101.0
A vent must rise vertically to at least what point before it may offset horizontally, to keep waste water out of the dry vent?
- a.2 inches above the trap weir
- b.12 inches above the floor
- c.at least 6 inches (152 mm) above the flood-level rim of the fixture served✓
- d.the center line of the drain
A vent must rise vertically to at least 6 inches above the flood-level rim of the fixture it serves before it may run horizontally. Below that height the pipe could carry or hold waste water, which would obstruct the vent. Keeping the horizontal offset above the flood-level rim keeps the dry vent dry.2022 California Plumbing Code (CPC) §905.0
For a 2-inch trap arm, the maximum developed length from the trap weir to the vent (per the CPC trap-to-vent table) is approximately…
- a.3 feet
- b.2 feet
- c.5 feet (for 2-inch pipe)✓
- d.3 feet 6 inches
The maximum trap-to-vent distance grows with pipe size: about 2 ft 6 in for 1-1/4 inch, 3 ft 6 in for 1-1/2 inch, and 5 feet for 2-inch pipe. Exceeding the distance risks self-siphoning the trap because the vent is too far to relieve pressure. The trap arm must also maintain proper slope within this length.
Besides not being directly beneath a door, openable window, or air intake, a side-wall (through-wall) vent termination must also maintain required clearance from…
- a.the water meter
- b.the lot/property line and building openings, per code✓
- c.the electrical panel
- d.the gas meter only
A through-wall vent terminal must keep the code-required distances from building openings and the property/lot line so sewer gas does not drift back indoors or onto a neighbor's lot. Through-wall terminations are also protected against birds and rodents with a screen or cap. Roof termination is preferred where a through-wall vent cannot meet the clearances.
An air admittance valve for an individual or branch fixture vent must be a listed device complying with which standard?
- a.ASME A112.6
- b.ASSE 1070
- c.ASSE 1017
- d.ASSE 1051✓
Individual and branch-type air admittance valves must be listed to ASSE 1051. Stack-type AAVs are covered by a different listing (ASSE 1050). Using a valve listed to the correct standard ensures it seals against sewer gas and admits air reliably.2022 California Plumbing Code (CPC) §918.0
Where a vent penetrates the roof, the plumber must provide…
- a.a pressure-reducing valve
- b.a cleanout at the roof
- c.a backwater valve
- d.a flashing (jacket) to make the roof penetration watertight✓
Every vent that passes through the roof must be made watertight with a proper flashing or roof jacket. Without it, rainwater would leak into the structure around the pipe. The flashing is sealed to both the roofing and the vent pipe.
A sewage sump that receives water-closet discharge and is served by a pump must be provided with a vent that…
- a.connects to the pump discharge line
- b.may be omitted if the pump is sealed
- c.is 1/2 inch minimum
- d.is sized per code and connects to the building vent system or extends independently to open air✓
A sealed sewage sump requires a vent, sized per code, that either ties into the building vent system or runs independently to the outside. The vent equalizes pressure as the sump fills and the pump discharges, and releases sewer gas outdoors. It must never connect to the pump discharge or be omitted.2022 California Plumbing Code (CPC) §710.0
For a building where sewage must be pumped and continuity of service is essential (such as public use), the CPC generally requires…
- a.a single large pump only
- b.no pump, only a holding tank
- c.a gravity bypass to the roof
- d.duplex (two) pumps or ejectors so one can operate if the other fails✓
Where interruption of pumping would create a health hazard, such as buildings used by the public, duplex pumps are required so that a standby unit takes over if one fails. The pumps typically alternate and can run together during peak flow. A single pump risks a sewage backup during any failure.2022 California Plumbing Code (CPC) §710.0
Sub-soil drains, foundation drains, and other clear-water drainage collected below sewer level should discharge to…
- a.the vent stack
- b.a separate sump that pumps clear water to an approved point of disposal, kept separate from sewage✓
- c.a grease interceptor
- d.the sanitary sewer directly
Clear-water drainage such as foundation and sub-soil drains must be collected in its own sump and pumped to an approved disposal point, not mixed with sanitary sewage. This avoids overloading the sanitary system with ground water and keeps a clean-water pump from handling sewage. The clear-water sump does not need to be gastight like a sewage sump.2022 California Plumbing Code (CPC) §710.0
An interior rainwater leader (a vertical storm pipe that carries storm water through a building) must be…
- a.vented like a sanitary stack
- b.connected to the sanitary building drain
- c.installed and, where it connects to a horizontal storm drain, sized to handle the roof area served✓
- d.trapped with a grease interceptor
An interior rainwater leader (conductor) must be sized for the roof area it drains and connected to a properly sized horizontal storm drain, kept separate from sanitary piping. Because storm systems carry no sewage, they are not vented like sanitary stacks, though offsets and connections still follow the storm-drainage rules. Where a leader could receive sewer gas, a trap is required.2022 California Plumbing Code (CPC) §1101.0
When a primary roof drain could become blocked and allow water to pond on the roof, the code requires…
- a.a backwater valve on the roof drain
- b.a secondary (overflow) roof drainage system or scuppers with independent discharge✓
- c.no additional provision
- d.a larger sanitary vent
Roofs must have a secondary (overflow) drainage system, such as overflow drains or scuppers, in case the primary roof drains clog. The overflow discharges independently so that a blockage does not let water accumulate to a structurally dangerous depth. This protects the roof structure from collapse under ponding loads.2022 California Plumbing Code (CPC) §1101.0
A hydromechanical grease interceptor is typically installed…
- a.after the building trap
- b.on the vent line
- c.as close as practical to the fixtures served, with a flow-control device limiting flow to its rated GPM✓
- d.inside the water closet
A hydromechanical grease interceptor should be located as close as practical to the fixtures it serves so grease is captured before it cools and adheres to piping. A flow-control fitting restricts flow to the unit's rated GPM, giving grease time to separate. It must remain accessible for regular cleaning.2022 California Plumbing Code (CPC) §1014.0
A small under-the-sink hydromechanical grease trap rated to PDI standards commonly has a flow rating such as…
- a.5 GPM
- b.20 or 25 GPM with a matching grease capacity✓
- c.100 GPM
- d.500 GPM
Point-of-use grease traps are commonly rated at low flows such as 20 or 25 GPM, matched to a corresponding grease-retention capacity in pounds. A flow-control fitting holds the flow at that rating so grease can separate. Larger loads require larger hydromechanical units or a gravity interceptor.2022 California Plumbing Code (CPC) §1014.0
An indirect-waste standpipe receiving a domestic clothes washer must have a trap, and the standpipe height above the trap weir must generally be within what range?
- a.12 to 16 inches
- b.6 to 12 inches
- c.36 to 48 inches
- d.18 to 30 inches (457–762 mm)✓
A clothes-washer standpipe must be trapped and vented, and the standpipe usually extends between 18 and 30 inches above the trap weir. Too short a standpipe can overflow during the wash pump-out; too tall creates back-pressure and slow draining. The trap is set at an accessible height below the standpipe.2022 California Plumbing Code (CPC) §804.0
What distinguishes an 'air break' from an 'air gap' in an indirect waste installation?
- a.An air break lets the indirect pipe terminate below the receptor's flood-level rim (the pipe may touch the receptor), while an air gap keeps a physical separation above the flood-level rim✓
- b.They are identical terms
- c.An air gap allows the indirect pipe to be submerged
- d.An air break always has a larger separation than an air gap
An air gap is an unobstructed vertical separation above the flood-level rim of the receptor, giving full protection against back-siphonage. An air break allows the indirect drain to end below the flood-level rim, even touching the receptor, but not submerged. Higher-hazard equipment (like food equipment) requires the full air gap, while lower-hazard drains may use an air break.2022 California Plumbing Code (CPC) §801.0