Free C-36 Practice Questions: Finish Plumbing Installations
60 free questions with answers, explanations and the official source for each. Answer one to see why. No sign-up.
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A restaurant's kitchen drain lines connected to a gravity grease interceptor total 21 drainage fixture units (DFUs). Under CPC Table 1014.3.6, what interceptor volume is listed for that load?
CPC Table 1014.3.6 (Gravity Grease Interceptor Sizing) lists 500 gallons for 8 DFUs, 750 gallons for 21 DFUs, and 1000 gallons for 35 DFUs.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 1014.3.7
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A private school (E occupancy) has a total occupant load of 300. Under CPC Section 422.1.1 and Table 422.1, what is the minimum number of water closets required for females?
CPC Section 422.1.1 splits the total occupant load 50 percent male and 50 percent female, so half of 300 are female. Table 422.1 requires 1 water closet per 30 females in an E occupancy, which gives 5 water closets.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 422.1.1
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Under CPC Section 408.6, how much lower than the sides and back of a shower receptor must its finished dam, curb, or threshold be?
CPC Section 408.6: where a shower receptor has a finished dam, curb, or threshold, it shall be not less than 1 inch lower than the sides and back of the receptor.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 408.6
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Under CPC Section 603.5.12, how must the potable water supply to a carbonated beverage dispenser be protected?
CPC Section 603.5.12: the potable water supply to carbonated beverage dispensers shall be protected by an air gap or a vented backflow preventer that complies with ASSE 1022, and piping downstream of the backflow preventer shall not be affected by carbon dioxide gas.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 603.5.12
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A tank fill spout has an effective opening of 2 inches in diameter, and the air gap is not affected by sidewalls. Under CPC Table 603.3.1, what is the minimum air gap?
CPC Table 603.3.1: for effective openings greater than 1 inch in diameter, the air gap is two times the diameter of the effective opening where not affected by sidewalls (three times where affected). Two times 2 inches is 4 inches.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) Table 603.3.1
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Under CPC Section 422.7, how far outward from the wall surface must the walls or partitions between urinals extend, at minimum?
CPC Section 422.7: urinal walls shall extend outward from the wall surface not less than 18 inches.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 422.7
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Under California Building Code Section 11B-604.3.1, what is the minimum clearance around an accessible water closet, measured perpendicular from the rear wall?
CBC 11B-604.3.1: clearance around a water closet is 60 inches minimum measured perpendicular from the side wall and 56 inches minimum measured perpendicular from the rear wall.
Under CPC 606.5, where must a control valve be installed?
CPC 606.5: a control valve shall be installed immediately ahead of each water-supplied appliance and immediately ahead of each slip joint or appliance supply. With a parallel (manifold) system, the valve may instead be at the manifold, identified with the fixture it serves.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 606.5
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Under CPC Section 504.3.2, what is the minimum clearance on all sides for an unlisted water heater?
CPC Section 504.3.2: unlisted water heaters must be approved by the Authority Having Jurisdiction before installation, and their clearance shall be not less than 12 inches on all sides.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 504.3.2
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Under CPC 1004.1, which of these traps is prohibited?
CPC 1004.1 prohibits "S" traps, bell traps, and crown-vented traps, and does not allow a fixture to be double trapped. Drum and bottle traps are installed for special conditions.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 1004.1
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A lawn sprinkler system has no pumps and no chemical injection. Under CPC Section 603.5.6, which of these devices may protect its potable water supply?
CPC Section 603.5.6: potable water supplies to sprinkler and irrigation systems with no pumps and no chemical injection shall be protected by an atmospheric vacuum breaker (AVB), a pressure vacuum breaker backflow prevention assembly (PVB), a spill-resistant pressure vacuum breaker (SVB), a reduced-pressure principle assembly (RP), or a valve complying with IAPMO PS 72.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 603.5.6
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Under California Building Code Section 11B-308.2.1, where a forward reach is unobstructed, what is the maximum high forward reach above the finish floor?
CBC 11B-308.2.1: where a forward reach is unobstructed, the high forward reach is 48 inches maximum and the low forward reach is 15 inches minimum above the finish floor or ground.
Under CPC 507.13, a gas water heater installed in a residential garage must have its burners and burner-ignition devices located at least how high above the floor, unless it is a listed FVIR appliance?
CPC 507.13: appliances in residential garages shall be installed so that all heating elements, switches, burners, and burner-ignition devices are located not less than 18 inches above the floor. Listed flammable vapor ignition resistant (FVIR) appliances are an exception.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 507.13
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Under CPC Section 505.4.1, what heat transfer medium may be used in an indirect-fired water heater that has a single-wall heat exchanger?
CPC Section 505.4.1: in an indirect-fired water heater with a single-wall heat exchanger, the heat transfer medium shall be either potable water or contain fluids recognized as safe by the FDA as food grade.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 505.4.1
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Under CPC Table 1002.2 (Horizontal Lengths of Trap Arms), what slope must a trap arm maintain?
Note 1 of CPC Table 1002.2 (Horizontal Lengths of Trap Arms): maintain a 1/4 inch per foot slope.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) Table 1002.2
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Under CPC Section 402.6.1, what is the minimum overall depth of a caulked-on closet ring (closet flange)?
CPC Section 402.6.1: caulked-on closet rings shall be not less than 1/4 of an inch thick and not less than 2 inches in overall depth.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 402.6.1
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Under California Building Code Section 11B-609.4, at what height are grab bars installed above the finish floor, measured to the top of the gripping surface?
CBC 11B-609.4: grab bars are installed in a horizontal position, 33 inches minimum and 36 inches maximum above the finish floor, measured to the top of the gripping surface.
Under CPC Section 412.1.3, where nonwater urinals are installed, what must be installed upstream on the same drain line?
CPC Section 412.1.3: where nonwater urinals are installed, not less than one water supplied fixture rated at not less than 1 water supply fixture unit (WSFU) shall be installed upstream on the same drain line to facilitate drain line flow and rinsing.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 412.1.3
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Under CPC Table 610.3, what is the minimum fixture branch pipe size for a 1.6 GPF flushometer valve water closet?
CPC Table 610.3 lists a 1 inch minimum fixture branch pipe size for a 1.6 GPF flushometer valve water closet, compared with 1/2 inch for a 1.6 GPF gravity tank water closet.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) Table 610.3
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Under CPC Section 603.4.9, where are backflow prevention devices with atmospheric vents or ports prohibited from being installed?
CPC Section 603.4.9: backflow prevention devices with atmospheric vents or ports shall not be installed in pits, underground, or submerged locations, and backflow preventers shall not be located where there are toxic, poisonous, or corrosive fumes.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 603.4.9
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A water closet flushometer valve is equipped with an atmospheric vacuum breaker. Under CPC Section 603.5.1, how high above the overflow rim of the bowl must its critical level be?
CPC Section 603.5.1: the atmospheric vacuum breaker shall be installed on the discharge side of the flushometer valve with the critical level not less than 6 inches, or the distance according to its listing, above the overflow rim of a water closet bowl or the highest part of a urinal.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 603.5.1
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Under CPC Table 1014.3.6, what interceptor volume is listed for a gravity grease interceptor serving kitchen drain lines with 8 drainage fixture units (DFUs)?
CPC Table 1014.3.6 (Gravity Grease Interceptor Sizing) lists an interceptor volume of 500 gallons for 8 DFUs; the next row is 750 gallons for 21 DFUs.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 1014.3.7
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Under CPC Section 408.8, a shower receptor's subfloor and rough side of walls are lined to a height of at least how far above the top of the finished dam or threshold?
CPC 408.8: shower receptors have the subfloor and rough side of walls, to a height of not less than 3 inches above the top of the finished dam or threshold, lined with sheet plastic, lead, copper, or other durable and watertight materials.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 408.8.3
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A gas water heater sits in a separate, enclosed space that can be entered only from outside of the garage. Under CPC Section 507.13.2, may it be installed at floor level?
CPC Section 507.13.2: where appliances are installed in a separate, enclosed space having access only from outside of the garage, they may be installed at floor level, provided the required combustion air is taken from the exterior of the garage.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 507.13.2
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Under California Building Code Section 11B-605.2, what is the maximum height of the rim of an accessible wall-hung urinal above the finish floor?
CBC Section 11B-605.2: urinals shall be the stall-type or the wall-hung type with the rim 17 inches maximum above the finish floor or ground.
What is the relationship between trap arm length and diameter in determining code compliance?
CPC Table 1002.2: 1-1/4 inch 30 inches, 1-1/2 inch 42 inches, 2 inch 60 inches, 3 inch 72 inches, 4 inch 120 inches, and never less than two pipe diameters.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) Table 1002.2
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Under California Building Code Section 11B-604.5.2, what is the minimum length of the rear wall grab bar at an accessible water closet, where wall space allows it?
CBC Section 11B-604.5.2: the rear wall grab bar shall be 36 inches long minimum and extend from the centerline of the water closet 12 inches minimum on one side and 24 inches minimum on the other side.
Under CPC 402.2, where a fixture comes in contact with the wall or floor, what must the joint between them be?
CPC 402.2: where a fixture comes in contact with the wall or floor, the joint between the fixture and the wall or floor shall be made watertight.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 402.2
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Under CPC 1012.1, laundry equipment in a commercial building without integral strainers must discharge into an interceptor with a removable wire basket that stops solids of what size or larger from passing into the drainage system?
CPC 1012.1: laundry equipment in commercial and industrial buildings that does not have integral strainers shall discharge into an interceptor with a wire basket or similar device, removable for cleaning, that prevents solids 1/2 inch or larger (string, rags, buttons and the like) from passing into the drainage system.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 1012.1
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Under CPC Section 420.3 and Table 420.3, what is the maximum flow rate of a Product Class 2 (more than 5.0 and up to 8.0 ounces-force) commercial pre-rinse spray valve?
CPC Section 420.3 and Table 420.3: a Product Class 2 pre-rinse spray valve (more than 5.0 and up to 8.0 ounces-force) has a maximum flow rate of 1.20 gpm.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 420.3
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Under CPC Table 603.3.1, what is the minimum air gap for a fixture whose effective opening is not greater than 1/2 inch in diameter, where it is not affected by sidewalls?
CPC Table 603.3.1 (Minimum Air Gaps for Water Distribution): for effective openings not greater than 1/2 inch in diameter, the air gap is 1 inch where not affected by sidewalls and 1-1/2 inches where affected by sidewalls.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) Table 603.3.1
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Under California Building Code Section 11B-306.3.2, what is the maximum depth that knee clearance extends under an element at 9 inches above the finish floor?
CBC 11B-306.3.2: knee clearance extends 25 inches maximum under an element at 9 inches above the finish floor or ground.
A spa is equipped with a submerged fill line. Under CPC Section 603.5.21, how must its potable water supply be protected?
CPC Section 603.5.21: the potable water supply to swimming pools, spas, and hot tubs shall be protected by an air gap or a reduced pressure principle backflow preventer where the unit has a submerged fill line or the supply is directly connected to the circulation system.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 603.5.21
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Under the CPC 202.1 definition, what does a grease interceptor intercept from a wastewater discharge?
CPC 202.1 defines a grease interceptor as a plumbing appurtenance or appliance installed in a sanitary drainage system to intercept nonpetroleum fats, oil, and greases (FOG) from a wastewater discharge.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 202.1
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A closet holds a 40,000 Btu/h water heater and a 60,000 Btu/h furnace. Combustion air comes from two permanent openings that communicate directly with the outdoors. Under CPC Section 506.4.1, what is the minimum free area of each opening?
CPC Section 506.4.1: each opening directly communicating with the outdoors needs 1 square inch per 4000 Btu/h of the total input rating of all appliances in the enclosure. 40,000 plus 60,000 Btu/h, divided by 4000, is 25 square inches for each opening.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 506.4.1
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Under CPC Section 407.2.4, what is the maximum volume a metered faucet may deliver per metering cycle?
CPC Section 407.2.4: metered faucets shall deliver a maximum of 0.2 gallons per metering cycle.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 407.2.4
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Under CPC 1011.1, a wash rack or floor used for cleaning machinery or machine parts must drain or discharge into what?
CPC 1011.1: a private or public wash rack, floor, or slab used for cleaning machinery or machine parts shall be adequately protected against storm or surface water and shall drain or discharge into an approved interceptor (clarifier).
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 1011.1
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Under California Building Code Section 11B-608.4, in which accessible showers is a folding seat provided?
CBC 11B-608.4: a folding seat is provided in roll-in type showers and transfer type shower compartments. In residential dwelling units, seats are not required where wall reinforcement has been installed so a seat can be added.
Under the CPC 202.1 definition, what is a cross-connection?
CPC 202.1 defines a cross-connection as a connection or arrangement, physical or otherwise, between a potable water supply system and a plumbing fixture or a tank, receptor, equipment, or device, through which it may be possible for nonpotable, used, unclean, polluted, and contaminated water, or other substances, to enter any part of the potable water system under any condition.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 202.1
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Under CPC 608.2, an approved pressure regulator must be installed where the static water pressure in the water supply piping exceeds what value?
CPC 608.2: where static water pressure in the water supply piping exceeds 80 psi, an approved-type pressure regulator preceded by an adequate strainer shall be installed and the static pressure reduced to 80 psi or less.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 608.2
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Under CPC Section 408.8.3, a hot-mopped shower subpan built up on the job site must have at least how many layers of standard grade 15 pound asphalt impregnated roofing felt?
CPC Section 408.8.3: nonmetallic shower subpans or linings built up on the job site shall be not less than three layers of standard grade 15 pound asphalt impregnated roofing felt, each layer hot-mopped to the one below.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 408.8.3
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Under CPC Section 603.4.4, where potable water is discharged to the drainage system, what air gap is required?
CPC Section 603.4.4: where potable water is discharged to the drainage system, it shall be by an approved air gap of two pipe diameters of the supply inlet, but in no case less than 1 inch. Direct connections between potable water piping and sewer-connected wastes are not permitted.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 603.4.4
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Under California Building Code Section 11B-608.6, what is the minimum hose length of the shower spray unit in an accessible shower compartment?
CBC Section 11B-608.6: a shower spray unit with a hose 59 inches long minimum, usable both as a fixed-position shower head and as a hand-held shower, shall be provided, and it shall deliver water that is 120°F maximum.
Under California Building Code Sections 11B-606.4 and 11B-309.4, how must the controls of accessible lavatory faucets operate?
CBC 11B-606.4: controls for faucets comply with Section 11B-309. CBC 11B-309.4: operable parts work with one hand, without tight grasping, pinching or twisting of the wrist, and need 5 pounds of force maximum.
Under CPC 507.2, where must a water heater be strapped to resist horizontal displacement from earthquake motion?
CPC 507.2: water heaters shall be anchored or strapped to resist horizontal displacement due to earthquake motion, with strapping at points within the upper one-third and lower one-third of its vertical dimensions. At the lower point, a distance of not less than 4 inches shall be maintained above the controls.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 507.2
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Under the CPC 202.1 definitions, both are mixing valves. How does a thermostatic (temperature control) valve differ from a pressure-balancing valve?
CPC 202.1: a thermostatic (temperature control) valve is a mixing valve that senses outlet temperature and compensates for fluctuations in incoming hot or cold water temperatures. A pressure-balancing valve is a mixing valve that senses incoming hot and cold water pressures and compensates for fluctuations in either to stabilize outlet temperature.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 202.1
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When installing two toilets in the same bathroom, what is the minimum center-to-center distance between them?
CPC 402.5: no water closet closer than 15 inches from its center to a side wall or obstruction, or 30 inches center to center to a similar fixture, with at least 24 inches of clear space in front.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 402.5
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A water heater sits in an attic above a finished ceiling. Under CPC Section 507.5, what is the minimum diameter of the drain from its drainage pan?
CPC Section 507.5: the drainage pan shall be provided with not less than a 3/4 of an inch diameter drain to an approved location, and the terminating end of the drainpipe shall be readily visible.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 507.5
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CPC Table 702.1 lists a service or mop basin with two trap sizes. What is the smaller of the two minimum trap and trap arm sizes?
CPC Table 702.1 lists a service or mop basin with a 2-inch trap and with a 3-inch trap, each rated 3.0 drainage fixture units (public and assembly).
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) Table 702.1
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A builder roughs in drain and water piping for a bathroom that will be finished later. Under CPC Section 402.11, how must construction for future installations be terminated?
CPC Section 402.11: construction for future installations shall be terminated with a plugged fitting or fittings, and the future fixtures are counted when sizing the drain and water supply piping.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 402.11
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Under CPC Section 412.1, what is the maximum average water consumption per flush for a wall-mounted urinal?
CPC Section 412.1: wall-mounted urinals shall have an average water consumption not to exceed 0.125 gallons per flush. Other urinals are limited to 0.5 gallons per flush.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 412.1
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A one-bedroom, one-bathroom house gets a new storage water heater. Under CPC Section 501.1 and Table 501.1(2), what is the minimum first-hour rating?
CPC Section 501.1: the minimum capacity for storage water heaters follows the first-hour rating in Table 501.1(2). For 1 to 1.5 bathrooms and 1 bedroom, the table lists 38 gallons. The first-hour rating is found on the Energy Guide label.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 501.1
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Under CPC 601.3.3, how must gray water system piping be identified?
CPC 601.3.3 requires alternate water source systems to have a purple (Pantone 512, 522C, or equivalent) background with uppercase lettering, and gray water systems to read CAUTION: NONPOTABLE GRAY WATER, DO NOT DRINK in black letters. Potable water is identified with a green background and white lettering under CPC 601.3.1.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 601.3.3
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Under CPC Table 603.2, a pressure vacuum breaker backflow prevention assembly must be installed a minimum of how many inches above all downstream piping and the flood-level rim of the receptor?
CPC Table 603.2: a pressure vacuum breaker backflow prevention assembly (loaded air inlet valve, internally loaded check valve and means for field testing) is installed in the upright position, may have valves downstream, and is a minimum of 12 inches above all downstream piping and the flood-level rim of the receptor.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) Table 603.2
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Under California Building Code Section 11B-604.7.1, how far in front of an accessible water closet must a toilet paper dispenser be, measured to the centerline of the dispenser?
CBC Section 11B-604.7.1: toilet paper dispensers shall be 7 inches minimum and 9 inches maximum in front of the water closet, measured to the centerline of the dispenser.
Under CPC Section 504.6, the hourly Btu discharge capacity of a water heater relief device must be at least equal to what?
CPC Section 504.6: the hourly Btu discharge capacity or the rated steam relief capacity of the device shall be not less than the input rating of the water heater.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 504.6
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Under California Building Code Section 11B-304.3.1, what is the minimum diameter of a circular turning space?
CBC 11B-304.3.1: a circular turning space is 60 inches in diameter minimum.
Under CPC 402.3, what must the screws or bolts that secure a floor-mounted fixture, such as a water closet, be made of?
CPC 402.3: floor-outlet or floor-mounted fixtures shall be rigidly secured to the drainage connection and to the floor, where so designed, by screws or bolts of copper, copper alloy, or other equally corrosion-resistant material.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 402.3
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Chemicals are added to a hot water boiler system. Under CPC Section 603.5.10, what backflow protection is required on its potable water connection?
CPC Section 603.5.10: potable water connections to steam or hot water boilers are protected by a double check assembly, a backflow preventer with intermediate atmospheric vent and pressure reducing valve, or an RP, but where chemicals are introduced into the system, a reduced pressure principle backflow prevention assembly shall be provided in accordance with Table 603.2.
Source: California Plumbing Code (CCR Title 24, Part 5) (2025) 603.5.10
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Under California Building Code Section 11B-609.3, what must the space between the wall and a grab bar be?
CBC Section 11B-609.3: the space between the wall and the grab bar shall be 1 1/2 inches.