General Requirements
14%of exam
PermitsPiping ProtectionInstallation & SupportBuilding DamageTesting
Fixtures
8%of exam
LocationsMaterials & ApprovalsInstallation & ClearancesFlow Rates & TempsFaucet Fittings
Water Heaters
12%of exam
InstallationT&P Relief ValveDischarge PipingThermal ExpansionFuel Gas & Venting
Water Supply and Distribution
21%of exam
Materials & JointsSizingBackflow PreventionPressure & VolumeWater Treatment
Sanitary Drainage
23%of exam
DFU LoadingPipe Sizing & SlopeCleanoutsTrapsIndirect Waste
Vents
22%of exam
Materials & GradesSizingTrap-to-Vent DistanceWet & Circuit VentsAAVs
Quick Facts
- Exam ID
- P1, Residential Plumbing Inspector
- Questions
- 60 multiple-choice
- Time Limit
- 2 hours
- Format
- Open book
- Passing Score
- Scaled score of 75
- Code Basis
- 2024 IRC, Chapters 25-33
- Validity
- 3 years
- Delivery
- Pearson VUE or ICC PRONTO
IRC Plumbing Chapter Range
Plumbing lives in IRC Chapters 25 through 33
25 Admin26-27 Fixtures28 Heaters29 Supply30 Drainage31 Vents
DWV Water Test vs Air Test
DWV Water Test
- 10 ft head minimum
- Hold 15 minutes
Water Supply Air Test
- 50 psi minimum
- Hold 15 minutes
Match the test method to system
Testing & Permit Thresholds
- DWV water test
- 10 ft head, hold 15 min
- Water supply air test
- 50 psi min, hold 15 min
- Permit required example
- water heater replacement
- Permit exempt example
- clearing stoppages, stopping leaks
- Notch limit 2x6 stud
- 25 percent depth, 1-3/8 in
- Bore limit bearing stud
- 40 percent of stud depth
- Firestop requirement
- approved system at fire wall
- Modification authority
- building official grants in writing
- Sleeve at foundation
- allows movement, seals water entry
Fixture Clearances & Approvals
- Water closet side clearance
- 15 in minimum from obstruction
- Water closet centerline spacing
- 30 in minimum apart
- Water closet front clearance
- 21 in minimum clear space
- Fixture approval basis
- listing, labeling, material standard
- Flow rate control
- max and min rates verified
- Temperature limiting control
- at fixture, not heater thermostat
Seismic Strap Memory Aid
Upper third and lower third with four inches over controls
Upper 1/3Lower 1/34 in above controlsSDC D0-D2 + C townhouse
Water Heater Safety Check
- T&P valve installed→Verify no isolation valve
- Discharge pipe routed→Check 6 in max height(no threads, rigid pipe)
- SDC D0-D2 or C townhouse→Require seismic strapping
- Storage tank in attic→Require an approved drain pan
Water Heater Safety Rules
- T&P valve isolation
- never permitted between tank
- T&P discharge height
- 6 in max above floor
- T&P discharge threads
- not permitted on end
- T&P discharge pipe
- rigid, no valve or trap
- Drain pan trigger
- where leakage could damage building
- Seismic strap zones
- SDC D0-D2 plus C townhouse
- Seismic strap points
- upper third and lower third
- Lower strap clearance
- 4 in above controls
- Thermal expansion trigger
- closed system, check valve present
Air Gap vs Backflow Preventer
Air Gap
- Physical separation
- No moving parts
- Visual verification
Mechanical Backflow Preventer
- Compact, in-line device
- Needs periodic testing
- Fits tight spaces
Use air gap when space allows
Backflow Protection Selection
- Direct cross-connection, high hazard→Reduced pressure principle assembly(continuous pressure use)
- Air gap achievable at fixture→Install approved air gap(2x opening, 1 in min)
- Hose bibb outdoor connection→Atmospheric vacuum breaker
- Boiler with chemical treatment→Air gap or RP assembly
- Irrigation system connection→Device per Table P2902.3
Water Supply & Backflow Rules
- Static pressure limit
- over 80 psi needs PRV
- Air gap sizing
- 2x opening, 1 in min
- Backflow device table
- Table P2902.3 by hazard
- Backsiphonage cause
- supply pressure drops below
- Backpressure cause
- downstream pressure exceeds supply
- Water hammer fix
- arrestor near quick-closing valve
- Hose bibb protection
- atmospheric vacuum breaker required
Backsiphonage vs Backpressure
Backsiphonage
- Supply pressure drops
- Vacuum pulls water back
Backpressure
- Downstream pressure rises
- Pushes water upstream
Match the device to the mechanism
DFU Quick Recall
Lav one, sink two, tub two, WC three or four
Lav 1Sink 2Tub 2WC 3-4
S-Trap vs P-Trap
S-Trap
- Self-siphons on discharge
- Prohibited configuration
P-Trap
- Vented trap arm
- Code-compliant design
S-trap is prohibited unvented risk
Cleanout Placement Decision
- Building drain meets sewer→Cleanout required at junction
- Horizontal branch, 2+ fixtures→Cleanout at the junction
- Direction change over 45 deg→Cleanout at that bend
- Multiple bends within 40 ft→One cleanout serves all
- Long straight horizontal run→Cleanout every 100 ft
Drainage Fixture Unit Values
- Water closet, 1.6 gpf
- 3 DFU
- Water closet, other
- 4 DFU
- Lavatory
- 1 DFU
- Bathtub or shower
- 2 DFU
- Kitchen sink
- 2 DFU
- Clothes washer standpipe
- 2 DFU
Drainage Slope & Cleanout Sizing
- Slope, 2.5 in or less
- 1/4 in per ft
- Slope, 3 in or more
- 1/8 in per ft
- Cleanout max interval
- 100 ft horizontal run
- Cleanout direction change
- required over 45 degrees
- Multiple bends in 40 ft
- one cleanout serves all
- Backwater valve trigger
- rim below upstream manhole
Traps & Indirect Waste
- Trap seal depth
- 2 in min, 4 in max
- S-trap status
- prohibited, self-siphons
- Water closet trap size
- 3 in minimum, no exceptions
- Indirect waste protection
- air break or air gap
Trap Arm Growth Pattern
Bigger trap arm allows a longer run to the vent
1-1/4 in = 30 in1-1/2 in = 42 in2 in = 60 in3 in = 72 in
Wet Vent vs Circuit Vent
Wet Vent
- Drain also vents fixtures
- Limited to bathroom group
Circuit Vent
- Vents a fixture battery
- Serves a horizontal branch
Both need an exact arrangement
Trap-to-Vent Distance Check
- Trap arm is 1-1/4 in→Max 30 in to vent
- Trap arm is 1-1/2 in→Max 42 in to vent
- Trap arm is 2 in→Max 60 in to vent
- Trap arm is 3 in→Max 72 in to vent
Vent Sizing & Trap-Arm Distance
- Min vent pipe size
- 1-1/4 in minimum
- Vent-to-drain ratio
- at least half drain diameter
- Trap arm, 1-1/4 in
- 30 in max to vent
- Trap arm, 1-1/2 in
- 42 in max to vent
- Trap arm, 2 in
- 60 in max to vent
- Trap arm, 3 in
- 72 in max to vent
AAV vs Open Vent
Air Admittance Valve
- Admits air only
- Mechanical, needs access
Open Vent
- Two-way air path
- Connects to outdoors
AAV never fully replaces open vent
Vent Terminals & Vent Types
- Vent terminal height
- 6 in above roof surface
- Snow climate vent
- 6 in above snow line
- Terminal near opening
- 10 ft, or 3 ft above
- Wet vent scope
- bathroom group, one floor
- AAV limitation
- no positive-pressure relief path
- Common vent condition
- method-specific fixture arrangement only
Common Traps
Confusing Trap Seal Limits
Minimum seal is 2 inches ≠ Maximum seal is 4 inches
S-Trap Looks Like P-Trap
S-trap self-siphons and fails ≠ P-trap with vent holds seal
Two Different Test Standards
DWV test needs 10 ft head ≠ Air test needs 50 psi minimum
Mixing Up Backflow Mechanisms
Backsiphonage is a pressure drop ≠ Backpressure is a pressure push
Assuming AAV Replaces Open Vent
AAV only admits air in ≠ System still needs outdoor vent
Slope Ratio Varies By Size
2.5-in pipe needs 1/4 slope ≠ 3-in pipe needs 1/8 slope
Cleanout Rule Depends On Layout
Straight runs cleanout every 100 ft ≠ Bend over 45 deg needs cleanout
Last Minute
- 1.Exam is 60 questions total
- 2.Time limit is two hours
- 3.Exam is open book format
- 4.Passing score is 75 scaled
- 5.Trap seal range is 2-4 in
- 6.Min vent size 1-1/4 in
- 7.Pressure over 80 psi needs PRV
- 8.Cleanouts required every 100 feet
- 9.T&P valve must never be isolated
- 10.Bring only approved code references
- 11.Tab your IRC before exam day
- 12.Six attempts allowed per six months
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