Exam Cheat Sheet · Quick Reference

Mississippi Plumbing

Mississippi · PSI Services Contractor

Verified, not estimated. Every figure below is drawn from the official exam structure we maintain — question counts, passing standard and topic weighting. Practice questions are grounded in the source law with statute citations. We omit any figure we can't verify rather than guess at it.

Total questions

Passing score

70%

Exam time

180 min

Administered by

PSI Services Contractor

Format

Reference materials allowed

Mississippi State Portion 70 questions

General Plumbing Regulations 4 Q · 6%

Plumbing system installation requirements and prohibited locationsMaterial identification, third-party certification, and standards compliancePipe and system protection (freezing, physical damage, corrosion, structural safety)Trenching, excavation, bedding, and backfill requirementsRequired tests and inspections (water, air, drainage, backflow, and shower liner tests)Piping support intervals and hanger spacing by material typeRodentproofing requirements for plumbing systemsCondensate disposal systems and auxiliary drain requirements

Safety 4 Q · 6%

Confined space identification, classification, and permit requirementsHazardous atmosphere recognition and atmospheric testing proceduresRoles and responsibilities of entry supervisors, attendants, and authorized entrantsConfined space rescue procedures and emergency servicesGeneral contractor safety and health provisions and employer responsibilitiesPersonal protective equipment requirements and selectionMedical services, first aid requirements, and emergency action plansPermissible exposure limits for airborne contaminants including lead

Cleanouts 4 Q · 6%

Cleanout placement intervals for horizontal drains, building drains, and building sewersCleanout requirements at changes of direction greater than 45 degreesCleanout size requirements relative to pipe size servedRequired clearance distances from cleanout openings to obstructionsCleanout access requirements and prohibited concealed locationsCleanout plugs: approved materials and head typesCleanout equivalents (fixture traps as substitutes)Prohibited use of cleanout openings for fixture or piping extensionsCleanout requirements at building drain and building sewer junctionCleanout installation at changes of horizontal direction greater than 45 degreesCleanout sizing requirements relative to pipe size servedRequired clearance distances for cleanout access openings +3 more

Fixtures and Equipment 5 Q · 7%

Minimum number of plumbing fixtures by occupancy classificationFixture material standards and quality requirementsInstallation clearances and spacing for fixturesWater closet and urinal requirements and prohibitionsShower compartment construction and lining requirementsFaucet and fixture fitting standards including temperature controlAccessible plumbing fixture requirementsWater heater installation safety devices and discharge pipingProhibited fixtures and fixture connectionsFixture material quality and standardsInstallation requirements for fixtures including spacing and clearancesFlushing devices for water closets and urinals +2 more

Water Heaters 2 Q · 3%

Temperature and pressure relief valve requirements and installationRelief valve discharge piping specificationsWater heater installation requirements and access clearancesSafety devices: antisiphon, vacuum relief, and shutdown provisionsWater heater pan requirements and drain terminationDrain valve requirements for tank-type water heatersWater temperature controls and maximum temperature limitsWater heater labeling, pressure markings, and insulation requirements

Piping, valves, controls 3 Q · 4%

Approved materials and standards for water service and distribution pipeApproved materials and standards for drainage and vent pipePipe joint and connection methods by material type (copper, PVC, CPVC, PEX, steel, cast iron)Valve types, placement requirements, and shutoff valve locationsBackflow prevention devices, types, and applicationsWater pressure requirements, pressure-reducing valves, and booster systemsPipe sizing for water distribution systemsProhibited joints, connections, and fitting types

Water Supply 6 Q · 9%

Backflow prevention devices, assemblies, and applicationsWater service pipe materials, standards, and sizing requirementsWater distribution system design criteria and pipe sizing methodsProtection of potable water supply from cross-connections and contaminationHot water supply system requirements and temperature controlsValve placement requirements for water supply and distribution systemsIndividual water supply systems, well construction, and disinfectionWater pressure regulation, booster systems, and water hammer arrestors

Hangers and Supports 3 Q · 4%

Pipe support intervals by material type (Table 308.5 horizontal and vertical spacing)Hanger and anchor material requirements and prohibition of galvanic actionStructural attachment of hangers and anchors to building constructionSway bracing for horizontal drainage pipes at direction changesAnchorage and restraint of drainage piping at changes in direction and diameterSeismic support requirements for plumbing pipingExpansion joint fittings for pipe expansion and contractionSupport requirements for thermal expansion tanks and parallel water distribution manifolds

Drain, Waste, and Vent 15 Q · 21%

Drainage fixture unit (DFU) values and fixture load calculationsSizing of horizontal drainage pipes, building drains, and building sewersSlope requirements for horizontal drainage pipingApproved materials for above-ground and underground drain, waste, and vent pipeVent system types and installation requirements (individual, common, wet, circuit, air admittance valves)Trap requirements, prohibited trap types, and trap seal protectionCleanout location, spacing, size, and access requirementsInterceptors and separators (grease, oil, sand) requirements and applications

Backflow 3 Q · 4%

Definitions of backflow, backsiphonage, backpressure, and cross connectionApplication and selection of backflow prevention devices by hazard level (Table 608.1)Types of backflow preventers and applicable standards (air gap, reduced pressure principle, double check, vacuum breakers, dual check)Protection requirements for specific connections (boilers, sprinkler systems, irrigation, beverage dispensers, hose connections, health care equipment)Installation requirements for backflow preventers (critical level, location, access, freeze protection)Inspection and testing of backflow prevention assemblies (annual inspections, testing standards per Section 312.10)Identification and labeling of nonpotable water systemsThermal expansion control where backflow preventers are installed on water heater supply

Traps and Interceptors 4 Q · 6%

Trap seal depth requirements and prohibited trap typesFixture trap installation requirements including distance limitations and double-trapping prohibitionTrap seal protection methods for floor drains subject to evaporationGrease interceptor requirements, sizing, and applicable facilitiesOil separator design and installation requirements for garages and service stationsSpecific interceptor requirements for clothes washers, bottling plants, and slaughterhousesVenting, access, and maintenance requirements for interceptors and separatorsSand interceptors and automatic grease removal devices

Developed length 2 Q · 3%

Center-to-center vs. end-to-end pipe length measurementsFitting allowance calculations for threaded, copper, and plastic fittingsDeveloped length measurement for cleanout spacing requirementsDiagonal and offset calculations using angle constantsDeveloped length of vent piping for sizing and distance limitationsConverting center-to-center measurements to cut lengthsDeveloped length measurement along drainage piping for trap-to-vent distance

Isometric Analysis 12 Q · 17%

Calculating center-to-center (c-c) pipe lengths from isometric drawingsCalculating end-to-end (e-e) pipe lengths using fitting allowances45-degree offset calculations using diagonal and offset constantsRise, run, and diagonal relationships in pipe offsetsThree-pipe offset diagrams with 45-degree fittingsRolling offsets and true offset calculationsParallel offset pipe length differences using spread constantsEqual spacing and pipe cut list calculations from isometric diagrams

Joints and Connections 3 Q · 4%

Joint types and methods for PVC plastic pipe (solvent cementing, mechanical, threaded, push-fit)Joint types and methods for copper and copper-alloy pipe and tubing (solder, brazed, mechanical, press-connect, push-fit)Joint types and methods for cast-iron pipe (caulked, compression gasket, mechanical coupling for hubless)Joint types and methods for ABS plastic pipe (solvent cementing, mechanical, threaded, push-fit)Joints between different piping materials (transition fittings, mechanical compression joints, dielectric fittings)Prohibited joints and connections in sanitary drainage and water supply systemsHeat-fusion joints for polyethylene, polyolefin, polyvinylidene fluoride, and polypropylene plastic pipeJoint types and methods for galvanized steel pipe (threaded and mechanical)

Key Distinctions

Mechanical JointvsSoldered/Threaded/Cemented Joint

A mechanical joint uses compression along the centerline and is NOT screwed, caulked, threaded, soldered, solvent cemented, brazed, welded, or heat fused, whereas the other types use one of those bonding methods.

International Plumbing Code 2021, Page 2-5

Flow PressurevsStatic Pressure

Flow pressure is measured in the supply pipe near an outlet while that outlet is wide open and flowing, whereas static pressure is measured with no flow occurring.

International Plumbing Code 2021, Page 2-4

Copper Fitting AllowancevsThreaded Fitting Allowance

Copper fitting allowance equals center-to-face minus solder-cup depth with no thread-in deduction, while threaded fitting allowance requires an additional thread-in deduction step.

Mathematics for Plumbers, Unit 10, Pages 56-57 (Allowances for Copper Fittings)

PVC (Plastic) Fitting AllowancevsThreaded Fitting Allowance

PVC fitting allowance is measured from center to the outside shoulder of the hub cup with no thread-in deduction, while threaded fitting allowance requires a thread-in deduction.

Mathematics for Plumbers, Unit 12, Pages 60-61 (Allowance for Plastic Fittings)

Copper Tubing Type K or L (Building Sewer)vsCopper Tubing Type M or DWV (Building Sewer)

Only Type K and L copper tubing are permitted for building sewer pipe; Types M and DWV are not permitted for that application.

IPC 2021, Table 702.3

Horizontal Drainage Pipe ≤2½ inch (Slope)vsHorizontal Drainage Pipe ≥8 inch (Slope)

Pipe 2½ inches or smaller requires a minimum slope of 1/4 inch per foot, whereas pipe 8 inches or larger requires only 1/16 inch per foot.

IPC 2021, Table 704.1

Short Sweep FittingvsSanitary Tee Fitting

A short sweep is acceptable for horizontal-to-horizontal changes in direction, while a sanitary tee is permitted only for horizontal-to-vertical connections.

International Plumbing Code 2021, Page 7-7 (Table 706.3)

Wet VentvsDry Vent

A wet vent carries the discharge of one fixture while simultaneously serving as the vent for another fixture, whereas a dry vent carries only air and no fixture discharge.

Island (Loop) VentvsConventional Dry Vent

An island/loop vent is used where no nearby wall is available for a vertical vent run (e.g., kitchen island), rising and looping back below the flood rim to a vented drain, while a conventional dry vent runs vertically up through a wall.

Segmented Loss Method Fitting Allowance Factor (IPC)vsAccepted Sizing Method Fitting Allowance Factor (IRC Appendix P / IPC E104)

The segmented loss method adds 50% of the developed length for fittings and valves, while the accepted sizing method multiplies the actual pipe length by a factor of 1.2 to compensate for fitting losses.

International Plumbing Code 2021, Page E-4 (Section E103.3, Step 6)

Drainage/Vent Air Test PressurevsWater Supply System Test Pressure

The drainage/vent air test requires a uniform gauge pressure of 5 psi held for not less than 15 minutes, while the water supply test requires not less than the system working pressure held for not less than 15 minutes.

Section 312.3

Permit-Required Faucet WorkvsPermit-Exempt Faucet Work

Repairing leaks in faucet valves and fixtures without replacing or rearranging valves, pipes, or fixtures is exempt from a permit, while any work involving replacement or rearrangement of valves, pipes, or fixtures requires a permit.

International Plumbing Code 2021, Page 1-4

Key Terms

Permit Application Abandonment (180-Day Rule) International Plumbing Code 2021, Page 1-4

Per IPC Section 106.3.2, a plumbing permit application is deemed abandoned 180 days after filing unless pursued in good faith or a permit has been issued; extensions not exceeding 180 days each may be granted.

Rough-In Inspection Prerequisites International Plumbing Code 2021, Page 1-5

Per IPC Section 108.2, the rough-in inspection shall occur after the roof, framing, fireblocking, firestopping, draftstopping, and bracing are in place and all sanitary, storm, and water distribution piping is roughed-in, but before wall or ceiling membranes are installed.

Backflow Prevention Assembly Annual Inspection International Plumbing Code 2021, Page 3-5, Section 312.10.1

Per IPC Section 312.10.1, all backflow prevention assemblies and air gaps shall be inspected annually to determine whether assemblies are operable and air gaps exist.

Thermal Expansion Tank Support International Plumbing Code 2021, Page 3-3, Section 308.10

Per IPC Section 308.10, a thermal expansion tank must be supported per manufacturer's instructions and shall NOT be supported by the piping that connects to it.

Water Supply System Pressure Test International Plumbing Code 2021, Page 3-5, Section 312.5

Per IPC Section 312.5, the water supply system shall be tested tight under a pressure not less than the system working pressure, held for not less than 15 minutes.

Shower Head Maximum Flow Rate International Plumbing Code 2021, Page 6-3 (Table 604.4)

Per IPC Table 604.4, the maximum flow rate for a shower head, including hand-held sprays, is 2.5 gpm at 80 psi.

Drainage/Vent Air Test (5 psi) Section 312.3

Per IPC Section 312.3, the drainage and vent system air test requires a uniform gauge pressure of 5 psi (or sufficient to balance a 10-inch mercury column) held for not less than 15 minutes; plastic piping shall not be air-tested.

Plastic Pipe NSF 14 Certification Section 303.3

Per IPC Section 303.3, plastic pipe, fittings, and components shall be third-party certified as conforming to NSF 14.

Steel Shield Plate Protection (No. 16 Gage) Section 305.6

Per IPC Section 305.6, piping other than cast iron or galvanized steel passing through framing members less than 1¼ inches from the nearest edge must be protected by steel shield plates not less than 0.0575 inch (No. 16 gage) thick.

Rock Excavation Clearance (3 inches) Section 306.2.2

Per IPC Section 306.2.2, where rock is encountered in trenching, it shall be removed to not less than 3 inches below the pipe installation level and backfilled with sand tamped in place.

PVC Pipe Hanger Spacing Table 308.5

Per IPC Table 308.5, PVC pipe hangers shall be spaced not more than 4 feet apart horizontally and not more than 10 feet apart vertically.

Cleanout Spacing (100-foot Maximum) Sanitary Drainage, Section 708.1.1

Per IPC Section 708.1.1, horizontal drainage pipes inside buildings shall have cleanouts located at intervals of not more than 100 feet.

Cleanout Clearance (18 inches) Sanitary Drainage, Section 708.1.10

Per IPC Section 708.1.10, cleanouts for 6-inch and smaller piping shall have not less than 18 inches of clearance perpendicular to the face of the opening to any obstruction.

Developed Length International Plumbing Code 2021, Page 2-3

Per IPC Section 202, developed length is the length of a pipeline measured along the centerline of the pipe and fittings, following the actual path including all fittings rather than the straight-line distance.

Effective Opening International Plumbing Code 2021, Page 2-3

Per IPC Section 202, effective opening is the minimum cross-sectional area at the point of water supply discharge, expressed as the diameter of a circle of equivalent area, measured at the smallest orifice in the fitting body or supply piping.

Conflict Between Code and Manufacturer Instructions Section 301.7

Per IPC Section 301.7, where conflicts occur between the plumbing code and manufacturer's installation instructions, the more restrictive provisions shall apply.

Formulas to Know

Static Pressure Loss Due to ElevationPressure loss (psi) = Elevation difference (ft) × 0.433 psi/ft

Segmented Loss Method — Equivalent Length of RunEquivalent length = Developed length × 1.50 (adds 50% for fittings and valves)

Accepted Sizing Method — Maximum Developed Length AdjustmentAdjusted length = Actual pipe length (source to most remote fixture) × 1.2

Horizontal Drainage Slope — Drop Over a RunTotal drop (in) = Pipe length (ft) × Slope (in/ft) [e.g., 1/4, 1/8, or 1/16 in/ft by pipe size]

Copper Fitting AllowanceFitting allowance = Center-to-face measurement − Depth of solder cup (no thread-in deduction)

PVC Fitting AllowanceFitting allowance = Center to outside shoulder of hub cup (no thread-in deduction; same process as copper)

Cut Length of PipeCut length = Face-to-face distance − Fitting allowances on each end

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