NBOPE Journeyperson Plumber cheat sheet

Pipe sizing convention: nominal trade sizes up to 12 in. refer to inside diameter for iron/steel; copper Type L 1/2 in. has roughly 5/8 in. OD and 0.545 in. ID - always verify against the actual product standard, not the nominal label.

Common copper types: K (heaviest wall, underground/buried), L (standard interior domestic water), M (thin wall, above-ground only where allowed), DWV (drainage). Color coding: K green, L blue, M red.

Plastic pipe service limits: PVC (Schedule 40/80) for cold water and DWV only; CPVC for hot and cold potable up to its listed temperature/pressure rating (commonly 100 psi at 180°F); PEX for hot/cold potable, with fittings matched to the same manufacturer's system.

Solvent cement joint sequence: cut square, deburr and chamfer, clean with primer, apply cement to both surfaces, assemble with a quarter-turn, hold, and allow full cure before pressure testing - cure time increases with pipe diameter and lowers with ambient temperature.

Threaded steel assembly: cut square, ream the inside burr, cut threads with the correct die, apply pipe dope or PTFE tape to male threads only (leaving the first thread bare), and make up hand-tight plus roughly 1 to 3 turns with a wrench.

Safety thresholds: OSHA 29 CFR 1926 Subpart P requires trench protective systems at 5 ft depth or greater (or when a competent person identifies a hazard); ladders used for access must extend at least 3 ft above the landing.

Confined-space entry: test the atmosphere for oxygen (19.5–23.5%), flammables, and toxics before entry; a permit and attendant are required for permit-required spaces. Never use an open flame or solvent near sewer gas.

Soldering: use lead-free solder and water-soluble or resin flux on cleaned copper; keep flame directed away from valves and heat-sensitive parts, purge the line of water, and never solder a line containing flammable gas or a closed pressurized system.

Slope rules: 2% (1/4 in. per ft) for pipe 2-1/2 in. and smaller and for 3–6 in. building drains/sewers where solids carry; 1% (1/8 in. per ft) is permitted only for larger pipe sizes and only where the code allows it.

Sanitary drainage uses gravity flow; a horizontal drain must be sized so flow depth does not exceed about half the pipe diameter. Fixture drain and branch minimum sizes are set by the fixture's drainage fixture unit (dfu) load.

Drainage fixture units (dfu) are not the same as water supply fixture units (wsfu). Example typical values: water closet 3–4 dfu, lavatory 1 dfu, bathtub 2 dfu, kitchen sink 2 dfu, floor drain 1–2 dfu depending on size.

A building drain is the lowest piping that receives soil and waste inside the building and conveys it to the building sewer; the building sewer runs from roughly 2 ft outside the foundation wall to the public sewer or private disposal.

Cleanouts are required at the base of each vertical stack, at the upper end of horizontal drains, at changes in direction greater than 135 degrees, and at intervals not exceeding 100 ft on horizontal runs (verify local amendments).

A trap arm (fixture drain) between the trap weir and the vent connection must not exceed the developed length allowed by the code for its size - commonly 5 ft for 1-1/2 in. and 6 ft for 2 in. - and must fall no more than one pipe diameter in that length.

A horizontal branch joining a vertical stack must enter through a wye (or combination wye and eighth bend), never a sanitary tee turned on its back. Sanitary tees are for vertical-to-horizontal flow direction only.

Backwater valves are required on drainage branches serving fixtures below the elevation of the next upstream manhole cover; the valve must be accessible for service.

Every trap must be vented. A vent protects the trap seal (typically 2 to 4 in. water column) by equalizing pressure so the seal is not siphoned or blown out by drainage flow.

A vent stack is the vertical vent serving a drainage stack; a stack vent is the extension of a soil/waste stack above the highest fixture branch. A vent terminal must extend at least 6 in. above the roof and be at least 3 ft from a door, window, or air intake (check local code for greater distances).

A common vent may serve two fixture drains at the same level when they connect to the same horizontal branch and the fixture drains enter the vent at or below the trap weir level; the vent must be sized for the combined load.

A wet vent is a vent that also serves as a drain for fixtures on the same floor; the wet-vented portion must be sized for the drainage load, and the fixtures must be on the same story with the vent taken above the trap weir.

An air admittance valve (AAV) admits air on drain but seals on positive pressure; it is permitted only where the code allows it, must be installed above the trap weir, and must be accessible and have a vented enclosure.

Trap types: P-trap (most common, integral or separate), S-trap (prohibited for new work because it siphons easily), drum trap (rarely allowed), and bell trap (limited use). Each fixture must have one trap, and no fixture may be double-trapped or trap-vented in series.

Vent sizing is based on the total fixture-unit load and the developed length; a vent must be at least 1-1/4 in. for most small fixtures and increase with load. A vent may not be reduced in size in the direction of flow.

A vent terminal must be located so it does not discharge near a window, door, or air intake; vent terminals must be at least 10 ft from a lot line in many jurisdictions and must be screened against vermin where required.

Water supply sizing uses water supply fixture units (wsfu) converted to a probable demand (gpm) through a fixture-unit-to-flow curve; the building main, meter, and each branch are then sized so velocity and pressure loss stay within limits (commonly 8 fps in small pipe, up to 10 fps in larger mains).

Minimum residual pressure rules: typically 8 psi flowing at the fixture for flush-tank water closets, 15 psi for flushometer valves, and a minimum of about 20 psi at the building main under peak flow (verify local code).

A pressure-reducing valve (PRV) is required where the static pressure exceeds the code limit (commonly 80 psi); an expansion tank or thermal expansion control is needed on a closed system with a backflow preventer or check valve.

Water supply fixture units (wsfu) typical values: water closet (flush tank) 2.5, lavatory 1, bathtub 1.5, shower 1.5, kitchen sink 1.5, hose bibb 2.5. Values differ by code and must be read from the adopted table.

A water service must be protected against backflow at the point of connection; a reduced-pressure principle assembly (RPZ) provides the highest protection and requires annual testing and accessible installation with adequate drain.

Recirculation systems keep hot water available: a dedicated return line with a pump, a thermostatic valve, or a gravity loop. Insulate all hot lines and keep dead legs short to reduce wait time and energy waste.

Water hammer is controlled with arrestors (air chambers or mechanical devices) installed near quick-closing valves; the arrestor must be sized for the fixture and installed in the same size as the branch.

When joining dissimilar metals, use dielectric unions or plastic spacers to prevent galvanic corrosion; copper and steel must never be in direct contact in a wet system.

Water closet flush volumes are limited by federal standard to 1.6 gallons per flush for tank-type toilets (1.28 gpf is common today) and 1.0 gpf for urinals; showerheads are limited to 2.5 gpm at 80 psi.

Fixture clearances: a water closet needs at least 15 in. from the centerline to a side wall and 21 in. in front of the bowl; a lavatory needs about 15 in. from centerline to a side wall and 21 in. clearance in front.

Flushometer valves require a minimum flowing pressure (often 15–25 psi depending on the valve) and a fixture with a matching flush rating; a pressure drop or undersized branch causes weak flush and short flush.

Fixture supply stops are required for each fixture (except where a single stop may serve a group), and the stop must be accessible. Fixture drains must be trapped individually, and a fixture may not be double-trapped.

Fixture materials: vitreous china for water closets and lavatories, cast iron or enameled steel for sinks and tubs, and stainless steel for commercial sinks. Fixtures must be listed and installed per manufacturer instructions.

A fixture's trap must be located as close as practical to the fixture outlet; the vertical distance from the fixture outlet to the trap weir may not exceed 24 in. in most codes, and the horizontal distance is limited.

Drinking fountains and bottle fillers must be protected against backflow and connected to a potable supply; the drain must be an indirect waste (air gap) where required by code.

Accessible fixtures (ADA): water closets 17–19 in. high to the seat top, lavatory rim at 34 in. maximum with knee clearance, and grab bars located per the accessibility standard. Verify the adopted edition.

A temperature and pressure relief (T&P) valve is required on every storage water heater and must be rated for the heater's input and pressure; the discharge pipe must be full size, slope downward, terminate within 6 in. of the floor or outside, and never be capped or trapped.

A thermal expansion tank is required on a closed system (one with a backflow preventer, check valve, or PRV). The tank precharge is set to the system static pressure and sized for the heater volume and temperature rise.

A water heater must have a drain pan with a drain to an approved location when leakage could cause damage, and the pan must be at least 1-1/2 in. deep with a 3/4 in. drain.

Combustion air: a gas water heater in a confined space needs two openings (high and low) sized to the input; a direct-vent or power-vent unit takes air from outside. A draft hood or draft diverter must not be modified.

A gas water heater in a garage must be elevated so the ignition source is at least 18 in. above the floor to avoid gasoline vapor ignition, unless it is listed as flammable-vapor-ignition-resistant.

Hot water distribution temperature: stored water is often kept at 120–140°F for scald control and storage capacity; a master tempering valve is used to deliver safe temperature at fixtures while keeping the tank hot enough to limit Legionella growth.

A recirculating hot water system with a pump and return line reduces wait time; the pump may be controlled by a timer, aquastat, or demand button. Insulate all hot lines and keep runs short.

Tankless (demand) heaters are sized by peak flow and temperature rise: flow (gpm) = input (Btu/hr) divided by (500 × temperature rise °F) for water. Check gas input capacity and venting requirements before installation.

Gas pipe sizing uses the longest developed length from the meter to the farthest appliance and the total connected load in Btu/hr; the pipe size is chosen from the code's capacity table for the gas type, pressure, and pipe material.

Typical natural gas heating value is about 1,000 Btu per cubic foot (varies by utility, often 1,000–1,050); propane is about 2,500 Btu per cubic foot. Always use the local utility's value for sizing.

A sediment trap (drip leg) is required at each appliance connection, installed as close as practical to the appliance and downstream of the shutoff valve, with a capped nipple at least 3 in. long.

A manual shutoff valve must be installed within 6 ft of the appliance and in the same room, and a union or flanged connection must be provided for appliance removal. A flexible connector must be listed for gas and not pass through a wall or floor.

Gas piping must be tested with air or inert gas at the pressure and duration required by code (commonly 10 psi for 15 minutes for low-pressure systems, or 3 psi for 10 minutes in some editions); the test must be witnessed by the inspector.

LP gas is heavier than air and settles in low areas; cylinders must be installed upright, secured, and at the required distance from ignition sources and building openings. A regulator is required at the cylinder and at the appliance where pressure demands it.

Bonding: gas piping must be bonded to the grounding electrode system, but the gas pipe must never be used as a grounding electrode or conductor. CSST may require a dedicated bonding conductor per manufacturer instructions.

Combustion air and venting: appliances must be listed for the vent type used (Category I, III, IV, direct vent). A blocked vent or improper slope of the vent connector can cause spillage of flue gases; a CO alarm should be installed per manufacturer and code.

Slope in percent = (fall ÷ run) × 100. A 1/4 in. per ft slope is (0.25 ÷ 12) × 100 = 2.08%. A 1/8 in. per ft slope is about 1.04%.

Fall = slope × run. For a 40 ft run at 1/4 in. per ft, fall = 10 in. For a 60 ft run at 1/8 in. per ft, fall = 7.5 in.

Pipe volume: gallons = 0.0408 × ID² (in.) × length (ft) for a full pipe. Example: 1 in. ID, 100 ft = 0.0408 × 1 × 100 = 4.08 gal.

Cylinder volume: V = π × r² × h. For a tank 24 in. diameter and 48 in. tall, r = 12 in., V = 3.1416 × 144 × 48 = 21,714 in.³ ÷ 231 = about 94 gal.

Fixture units: total dfu is the sum of each fixture's drainage fixture unit value; total wsfu is the sum of each fixture's water supply fixture unit value. Convert wsfu to gpm using the code's demand curve - do not add gpm values directly.

Pressure and head: 1 psi = 2.31 ft of water column. A 30 ft column of water exerts 30 ÷ 2.31 = about 13 psi. Static head loss must be subtracted from available pressure along with friction loss.

Friction loss is read from tables for the pipe material and flow rate; add equivalent lengths for fittings (a 90° elbow, tee, or valve adds a length of straight pipe). Total developed length = measured length + equivalent fitting length.

Drainage sizing: a 4 in. building drain at 1/4 in. per ft carries about 216 dfu in many code tables; verify the adopted table. Never size a drain below the minimum required by the fixtures it serves.

A plumbing permit is required before installing, altering, or replacing most plumbing systems; minor repairs such as replacing a faucet or a toilet seat generally do not require a permit, but replacing a water heater or adding a fixture usually does.

Plans and specifications must be submitted for review for larger projects; the permit must be posted on the job and inspections requested at required stages (underground, rough-in, and final).

Rough-in inspection occurs after piping is installed but before it is covered; the system must be tested (water or air) and the inspector must see the test. Concealing work before inspection is a violation.

Final inspection verifies fixtures, water heater installation, venting, backflow protection, and that all prior corrections are complete. A certificate of occupancy may depend on a passed final plumbing inspection.

The code official has authority to interpret the code and to require correction of unsafe conditions; a variance or appeal is filed with the board of appeals within the time stated by the local ordinance.

Licensing: a journeyman plumber works under a master plumber's license; the master is responsible for the permit and the work. Verify the license type and scope required by the jurisdiction before signing a contract.

When code editions conflict, the locally adopted edition governs. The model code (Uniform Plumbing Code or International Plumbing Code) applies only as amended by the local jurisdiction.

Inspectors may require a test of the drainage system with water (10 ft head or to the highest point) and the water supply at working pressure; record the test pressure, duration, and results for the inspection.

A cross-connection is any actual or potential link between a potable supply and a nonpotable source. It must be eliminated or protected by an approved backflow preventer.

Backflow occurs by backsiphonage (negative pressure in the supply) or backpressure (downstream pressure exceeds supply pressure). The protection device must match the hazard: air gap (highest), RPZ, double check, or vacuum breaker.

An air gap is the only protection that works for both backsiphonage and backpressure without mechanical parts; the gap must be at least twice the effective diameter of the supply pipe and never less than 1 in.

A reduced-pressure principle assembly (RPZ) protects against both backsiphonage and backpressure and is required for high-hazard connections; it must be tested at installation and annually by a certified tester.

A double check valve assembly protects against backpressure and backsiphonage for low-hazard connections only; it is not allowed for high-hazard or toxic connections.

Atmospheric vacuum breakers must be installed at least 6 in. above the highest downstream outlet (critical level) and are not allowed under continuous pressure for more than 12 hours.

Irrigation systems require backflow protection: a pressure vacuum breaker or RPZ at the point of connection, with the device located above the highest head and protected from freezing. Hose bibbs need vacuum breakers.

Water quality: lead service lines and lead solder are prohibited in potable systems; test for lead and copper where required. Chlorination and flushing are used to disinfect new or repaired mains, with a residual chlorine level verified before placing the line in service.

A cross-connection is any actual or potential link between a potable supply and a nonpotable source. It must be eliminated or protected by an approved backflow preventer.

Backflow occurs by backsiphonage (negative pressure in the supply) or backpressure (downstream pressure exceeds supply pressure). The protection device must match the hazard: air gap (highest), RPZ, double check, or vacuum breaker.

An air gap is the only protection that works for both backsiphonage and backpressure without mechanical parts; the gap must be at least twice the effective diameter of the supply pipe and never less than 1 in.

A reduced-pressure principle assembly (RPZ) protects against both backsiphonage and backpressure and is required for high-hazard connections; it must be tested at installation and annually by a certified tester.

A double check valve assembly protects against backpressure and backsiphonage for low-hazard connections only; it is not allowed for high-hazard or toxic connections.

Atmospheric vacuum breakers must be installed at least 6 in. above the highest downstream outlet (critical level) and are not allowed under continuous pressure for more than 12 hours.

Irrigation systems require backflow protection: a pressure vacuum breaker or RPZ at the point of connection, with the device located above the highest head and protected from freezing. Hose bibbs need vacuum breakers.

Water quality: lead service lines and lead solder are prohibited in potable systems; test for lead and copper where required. Chlorination and flushing are used to disinfect new or repaired mains, with a residual chlorine level verified before placing the line in service.