NCCER Plumbing cheat sheet

Minimum slope for horizontal drainage pipe: 1/4 in. per foot for pipe 2-1/2 in. and smaller (about 2% grade); 1/8 in. per foot is allowed for 3 in. and larger pipe only where the developed length permits adequate velocity under the governing code.

Drainage fixture unit (dfu) values are assigned by fixture type and code table; a water closet is commonly 3 dfu (public) or 4 dfu, a lavatory 1 dfu, a floor drain 2 dfu. Convert total dfu to pipe size using the code's building drain and branch tables.

Water supply sizing uses fixture units and the Hunter curves or code tables: total supply fixture units → demand in gpm → pipe size based on allowable velocity (typically about 8 fps in supply mains) and pressure loss.

Developed length of pipe equals the measured length plus allowances for fittings: a 90° elbow is commonly counted as an equivalent length of 2-1/2 to 3 ft for small pipe, a 45° elbow about 1-1/2 ft, and a tee about 5 ft (code tables govern).

Vent sizing rule: a vent must be at least 1-1/4 in. (commonly 1-1/2 in. for a water closet), and the vent must not be smaller than one-half the drain it serves in many code tables. Each fixture trap requires a vent unless it is a listed combination waste-and-vent or an approved wet vent.

Trap seal depth is 2 to 4 in.; a trap must be installed level, with a cleanout, and the fixture arm (trap arm) length from trap weir to vent is limited by pipe size (e.g., 1-1/2 in. trap arm ≈ 3-1/2 ft, 2 in. ≈ 5 ft).

Water heater safety: T&P relief valve discharge must terminate within 6 in. of the floor (or outside), never be capped or reduced, and the T&P valve is set to the tank rating (commonly 150 psi / 210°F). A thermal expansion tank is required on closed systems.

Pressure test requirements: DWV systems are typically tested with a 10 ft head of water (or 10 psi air where allowed) for at least 15 minutes without drop; water supply systems are tested at working pressure plus 50 psi (or code-specified) for at least 1 hour.

Backflow protection: an air gap is the highest-level protection; atmospheric vacuum breakers (AVB) cannot be under continuous pressure; reduced-pressure principle assemblies (RPZ) and double-check valves are used for cross-connection control per degree of hazard.

Copper tube sizing: Type K (thickest, green), Type L (blue), Type M (red, thinnest). Type L is common for plumbing; Type M is limited to above-ground, non-embedded use. Nominal size is not actual OD: 1/2 in. nominal copper has 5/8 in. OD.

Rough-in dimensions: a water closet rough-in is typically 12 in. from the finished wall to the drain center (10 in. and 14 in. also exist); a lavatory drain center is usually 17–18 in. above the floor; a shower valve is commonly 42 in. above the floor.

Soldering: use lead-free solder (95/5 or 50/50 only for non-potable where allowed), flux the tube and fitting, heat the fitting (not the solder), and draw solder into the joint; lead-free solder melts at about 420–460°F.

Press-fit and push-fit fittings require a square, burr-free cut, full insertion depth marked on the tube, and a deburring tool; press tools must be calibrated and the fitting not reused after pressing.

PVC solvent welding: cut square, chamfer, clean with primer, apply cement to both surfaces, assemble with a quarter-turn, and hold for 15–30 seconds; cure time depends on pipe size and temperature (e.g., 1-1/2 in. at 60–100°F ≈ 15 minutes before pressure testing).

Cast iron no-hub couplings: torque the clamps to the manufacturer's spec (commonly 60 in.-lb) with a calibrated torque wrench; the coupling sleeve must be centered on the joint.

Water pipe support spacing: copper horizontal 1/2–3/4 in. ≈ 6 ft, 1 in. ≈ 8 ft; PVC horizontal ≈ 4 ft for 1 in. and smaller; vertical support at each floor.

Fixture installation: set the water closet on a new wax ring (or waxless seal) with the closet flange flush with or slightly above the finished floor; secure the closet bolts and shim the base without cracking the china.

Gas piping: black iron pipe is joined with approved pipe dope or tape; a drip leg (sediment trap) is installed at the appliance, and the gas line is tested at 1-1/2 times working pressure (commonly 10 psi for 1/2 psi systems) for at least 30 minutes.

Safety: OSHA requires fall protection at 6 ft (general industry) or 10 ft (construction); a trench 5 ft or deeper requires a protective system (sloping, shoring, or shielding) unless in stable rock.

Confined space: a space with limited entry/exit, not designed for occupancy, and with a hazardous atmosphere requires a permit and atmospheric testing (O2 19.5–23.5%, LEL < 10%, H2S < 10 ppm) before entry.

Electrical safety: lockout/tagout (LOTO) must be applied before servicing equipment; use GFCI protection on temporary power; maintain 10 ft clearance from overhead power lines for equipment.

PPE: safety glasses with side shields, hearing protection above 85 dBA, gloves, and steel-toe boots; a respirator requires fit testing and medical clearance.

Hazard communication: SDS (Safety Data Sheet) must be available for every chemical; GHS pictograms identify hazards; store solvents away from open flame and in approved containers.

Lifting: keep the load close, bend at the knees, and use two-person lifts for loads over about 50 lb; use mechanical aids for pipe and water heaters.

Fire safety: a fire watch is required when hot work (soldering, brazing, cutting) is performed; keep a fire extinguisher rated for the hazard (ABC for general, BC for flammable liquids) and clear combustibles within 35 ft.

Excavation: spoil piles and equipment must be kept at least 2 ft from the trench edge; ladders in trenches must extend 3 ft above the top and be spaced within 25 ft of travel.

Reading plans: plumbing drawings use a plan view, riser diagram, and isometric; the riser diagram shows pipe sizes, slopes, and vent connections, while the plan shows fixture locations and pipe routing.

Scale: a 1/4 in. = 1 ft scale means 1/4 in. on the drawing equals 12 in. actual; use an architect's scale, not an engineer's scale, for building plans.

Symbols: a circle with a cross is a floor drain; a square with a diagonal is a cleanout; a triangle is a vent through roof; dashed lines indicate concealed pipe; a solid line is exposed pipe.

Specifications: Division 22 (Plumbing) of MasterFormat covers plumbing; Division 21 is fire suppression; Division 23 is HVAC. The specs govern materials, testing, and submittals, and take precedence over drawings when they conflict (per general conditions).

Takeoff: count fixtures by type, measure pipe runs by scale, add fittings by counting from the isometric, and apply waste factors (commonly 5–10% for pipe, 2–5% for fittings).

Elevations: floor drains are set 1/4 in. below the finished floor; a water heater is set on a stand or in a pan with a drain; a hose bibb is commonly 18 in. above grade.

Change orders: a change in the work must be documented in writing and priced before work proceeds; RFIs (requests for information) clarify drawings before installation.

Code hierarchy: the adopted plumbing code (e.g., IPC or UPC), local amendments, and the manufacturer's installation instructions all apply; the most restrictive requirement governs.

Troubleshooting a clogged drain: start at the fixture, use a hand auger or closet auger for a water closet, a drum auger for branch lines, and a power auger or jetter for mains; confirm the blockage location by testing fixtures upstream and downstream.

A gurgling fixture or slow drain across multiple fixtures suggests a blocked vent or a partially blocked main; a sewer smell indoors suggests a dry trap, a broken vent, or a failed wax ring.

Water hammer is caused by sudden valve closure; fix with air chambers, water hammer arrestors, or by replacing worn valves and securing loose pipe.

No hot water: check the power/gas supply, the thermocouple or igniter, the dip tube, and the lower heating element; a leaking T&P valve may indicate excessive pressure or a failed expansion tank.

Leak diagnosis: a water meter that moves with all fixtures off indicates a supply leak; a dye test in the tank identifies a leaking flapper; a smoke or peppermint test locates a broken vent or sewer line.

Pressure problems: low pressure at one fixture suggests a clogged aerator or cartridge; low pressure throughout suggests a failed pressure-reducing valve, a partially closed valve, or a supply line restriction.

Pump and ejector: a sewage ejector basin must be vented and the pump controlled by a float; a simplex system must have an alarm; check the check valve and the float before replacing the pump.

Testing and inspection: after repair, pressure-test the affected section, verify slope with a level, and confirm the trap seal; document the repair and any code-required inspection.

Water heater sizing: the first-hour rating (FHR) must meet peak demand; a storage tank's FHR depends on tank volume, recovery rate, and input BTU. A rule of thumb is 1 gallon per fixture for storage, but the code's sizing tables govern.

Gas water heater venting: a natural-draft water heater requires a vent connector with a minimum rise of 1/4 in. per foot and a draft hood; a Category III/IV appliance requires a listed vent and condensate management.

Tankless water heaters require a minimum flow rate to fire (commonly 0.5–0.75 gpm) and a gas supply sized for the full input; the vent must be listed for the appliance category.

Recirculation: a hot water return line or a dedicated recirculation pump reduces wait time; a thermostatic valve controls the return temperature; an on-demand system uses a push button or motion sensor.

Expansion tanks: a closed system requires a thermal expansion tank sized to the system volume and temperature rise; the tank precharge is set to the system's static pressure.

Water treatment: a water softener uses ion exchange resin and a brine tank; backwash and regeneration cycles are set by hardness and demand; a sediment filter is rated in microns.

Solar and heat pump water heaters: a heat pump water heater needs about 1,000 cubic feet of air space or ducted air; a solar system needs a backup element and a freeze-protection strategy.

Legionella control: store hot water at 140°F or higher and use a mixing valve to deliver 120°F or less at the fixture; flush unused fixtures and dead legs.

Pipe sizing for gas: use the longest length method from the code's gas pipe tables; the longest run from the meter to the farthest appliance determines the size for the total load, and each branch is sized for its own load and length.

Gas appliance load: a typical residential gas water heater is 40,000 BTU/hr, a furnace 80,000–100,000 BTU/hr, and a range 40,000–65,000 BTU/hr; add loads to size the meter and main.

Gas leak testing: a new system is tested at 1-1/2 times the working pressure (commonly 10 psi for a 1/2 psi system) for at least 30 minutes with a gauge; soap bubbles or an electronic detector locate leaks.

Combustion air: a confined space requires two permanent openings (one high, one low) sized per the code's free area (commonly 1 sq in. per 1,000 BTU/hr for a direct-connect opening, and 1 sq in. per 2,000 BTU/hr for a vertical duct).

Venting: a natural-draft appliance requires a vent with a draft hood and a minimum height above the roof (commonly 2 ft above the roof within 10 ft of a wall or ridge); a chimney must be lined and sized for the appliance.

Backdrafting: test for spillage at the draft hood with a mirror or smoke; a blocked flue, tight house, or undersized vent can cause backdrafting, which is a carbon monoxide hazard.

Gas piping materials: black steel pipe for above-ground, coated or wrapped pipe for underground, and listed CSST with bonding; a shutoff valve is required at each appliance.

Carbon monoxide: install CO alarms outside sleeping areas and on each level; a CO level of 9 ppm (8-hour) or 35 ppm (1-hour) is the EPA indoor air limit.

Fixture unit conversion: 1 water closet = 3 dfu (public) or 4 dfu (private), 1 lavatory = 1 dfu, 1 bathtub/shower = 2 dfu, 1 kitchen sink = 2 dfu, 1 floor drain = 2 dfu; total dfu from the code table gives the drain size.

Water supply fixture units (wsfu) differ from dfu: a water closet is 2.5 wsfu (flush tank) or 10 wsfu (flushometer), a lavatory 1 wsfu, a bathtub 4 wsfu, a shower 2 wsfu.

Building drain sizing: a 3 in. building drain handles about 20–35 dfu depending on slope; a 4 in. drain handles about 160 dfu at 1/4 in./ft; always use the code table, not memory.

Fixture spacing: a water closet must have at least 15 in. from its center to a side wall and 30 in. of clear space in front; a lavatory needs 4 in. from its center to a side wall.

Accessibility (ADA): a water closet centerline is 16–18 in. from the side wall, the seat height is 17–19 in., and a lavatory must have a knee clearance of 27 in. high and 8 in. deep.

Grease interceptor sizing: use the code formula (commonly 1 cubic foot per fixture or the formula based on fixture capacity and flow rate); a grease interceptor must be accessible for cleaning.

Storm drainage: roof drains are sized by the roof area and the local rainfall rate (inches per hour); a 4 in. leader handles about 1,700 sq ft at 1 in./hr, but the code table governs.

Water pressure: a pressure-reducing valve is required when the supply exceeds 80 psi; the typical delivered pressure is 45–60 psi; a pressure gauge is used to verify.

Soldering vs. brazing: soldering is below 840°F and uses lead-free solder for potable water; brazing is above 840°F and uses a filler such as Sil-Fos for high-temperature or medical gas work.

PEX: use a manifold or crimp/expansion system per the manufacturer; PEX must be protected from UV, supported every 32 in. horizontally, and not installed within 12 in. of a heat source.

Pipe cutting: a tubing cutter produces a square cut with a burr that must be reamed; a hacksaw cut must be squared and deburred; a plastic pipe cutter is used for PVC and CPVC.

Threading: use a die head sized to the pipe, oil the die, and cut threads to the proper length (about 3/4 in. for 1/2–3/4 in. pipe); a thread gauge verifies the thread.

Flaring: a flaring tool produces a 45° flare for flare fittings; the flare must be centered and not cracked; flare fittings are used for gas and refrigeration.

Joining plastic: CPVC requires a different cement than PVC; use the correct primer and cement for the material and pipe size, and allow the proper cure time before pressure testing.

Hangers and supports: use clevis hangers for horizontal pipe, riser clamps for vertical pipe, and insulators between dissimilar metals to prevent galvanic corrosion.

Insulation: pipe insulation is rated by R-value; a vapor retarder must face the warm side; a pipe in a freeze-prone area needs heat tape and insulation.

Project documents: a submittal is a product data sheet or shop drawing submitted for approval before installation; a shop drawing is a detailed fabrication/installation drawing prepared by the contractor.

Scheduling: a critical path method (CPM) schedule identifies the longest sequence of dependent tasks; a delay on the critical path delays the project.

Estimating: labor hours are estimated using a productivity rate (e.g., hours per fixture or per foot of pipe); material costs include waste, freight, and sales tax.

Quality control: a punch list is a list of incomplete or defective work identified at substantial completion; the contractor must correct items before final payment.

Coordination: use a clash detection review (BIM) to resolve conflicts between plumbing, HVAC, and electrical before rough-in; an RFI documents a conflict and requests clarification.

Safety program: a written hazard communication program, a competent person for excavations, and a site-specific safety plan are required on commercial projects.

Codes and permits: a permit is required before work begins; the inspector performs rough-in and final inspections; work must comply with the adopted code and approved plans.

Warranty and closeout: provide operation and maintenance manuals, as-built drawings, and training to the owner; the warranty period is defined by the contract.

Water heater installation: a water heater must be installed in a pan with a drain when leakage could cause damage, and it must be secured (strapped) in seismic zones; the T&P valve must be piped to a safe discharge.

Fixture carriers: a water closet carrier supports the fixture and connects to the drain; the carrier must be anchored to the structure and set at the correct rough-in height.

Floor drains: a floor drain requires a trap primer when the trap may evaporate; the drain body is set in the concrete with the clamping collar and membrane.

Shower pans: a shower pan requires a preslope (1/4 in. per foot) under the waterproof membrane, a clamping drain, and a weep hole path; the finished tile slope is also 1/4 in. per foot.

Water closet installation: the closet flange must be anchored to the floor and flush with the finished floor; the wax ring seals the outlet; the tank is bolted to the bowl with a gasket.

Faucet installation: use new supply lines and a new drain assembly; apply plumber's putty or silicone to the drain flange; check for leaks at the supply connections and the drain.

Dishwasher and ice maker: a dishwasher requires a high-loop or air gap for backflow protection; an ice maker requires a shutoff valve and a water hammer arrestor.

Sump pumps: the pump must discharge to a legal point (not to the sanitary sewer unless allowed), and the check valve prevents backflow; the pit must be covered.

Water supply demand: peak demand is calculated from fixture units using the code's demand tables; the meter and service line are sized for the total demand plus the fire sprinkler demand where applicable.

Pressure loss: friction loss in pipe is calculated with the Hazen-Williams formula; loss increases with flow and decreases with pipe diameter; fittings add equivalent length.

Pump sizing: a booster pump is sized for the required flow (gpm) and head (ft); the pump curve shows flow vs. head, and the operating point is where the system curve crosses the pump curve.

Backflow prevention: an RPZ assembly is tested annually and must be installed above grade with a drain; an air gap is the only protection that does not require testing.

Water softener sizing: size by grains of hardness per gallon × daily gallons = grains per day; the resin capacity and regeneration frequency determine the salt dose.

Filtration: a carbon filter removes chlorine and taste/odor; a sediment filter removes particulates; a reverse osmosis unit removes dissolved solids and requires a drain connection.

Hot water recirculation: a dedicated return line with a pump and a check valve keeps hot water at the fixture; a timer or aquastat controls the pump.

Cross-connection survey: identify all connections between potable and non-potable systems, including hose bibbs, boilers, irrigation, and chemical feed systems, and protect each with the appropriate device.

Vent types: a continuous vent is a vertical vent from a fixture drain; a revent connects two vents; a wet vent carries waste and serves as a vent for another fixture; a stack vent extends the soil stack through the roof.

Vent terminal: a vent must extend at least 6 in. above the roof (or 12 in. where snow accumulates) and at least 3 ft from a window or air intake; a vent must be at least 10 ft from a chimney.

Trap arm: the distance from the trap weir to the vent is limited by pipe size (1-1/4 in. ≈ 2-1/2 ft, 1-1/2 in. ≈ 3-1/2 ft, 2 in. ≈ 5 ft, 3 in. ≈ 6 ft, 4 in. ≈ 10 ft).

Sizing vents: a vent must be at least 1-1/4 in. and not less than one-half the drain size; a vent stack serving a building drain is sized by the total dfu.

Air admittance valves (AAV): an AAV is a one-way valve that admits air but does not allow sewer gas to escape; it must be installed in an accessible location and is limited to a single fixture or a small group.

Wet venting: a wet vent must be at least 2 in. and may serve only a water closet and one other fixture (per many codes); a wet vent cannot be a toilet drain for another toilet.

Vent slope: a horizontal vent must slope back to the drain at 1/4 in. per foot so condensate drains; a vent must not have a sag or trap.

Common vent: a common vent connects two fixture drains to a single vent; the vent must be sized for the combined load and the fixtures must be on the same floor.

Water quality: hardness is measured in grains per gallon (gpg); 0–3 gpg is soft, 3–7 is moderate, 7–10 is hard, and above 10 is very hard.

pH: a pH below 7 is acidic and can corrode copper pipe; a pH above 8.5 can cause scale; a neutralizing filter raises pH with calcite or magnesium oxide.

Iron and manganese: iron above 0.3 ppm causes staining; a greensand or oxidizing filter removes iron; manganese above 0.05 ppm causes black staining.

Chlorine: a carbon filter or an activated carbon block removes chlorine; a UV light is used to disinfect water but requires clear water (low turbidity) to work.

Backflow prevention: an air gap is the highest protection; an RPZ is used for high hazard; a double check is used for low hazard; a pressure vacuum breaker protects against backsiphonage only.

Water testing: test for bacteria (total coliform), nitrates, lead, and hardness; a private well should be tested annually for bacteria and nitrates.

Cross-connection control: a hose bibb requires a vacuum breaker; a boiler fill line requires a backflow preventer; an irrigation system requires an RPZ or a pressure vacuum breaker.

Water treatment maintenance: replace filter cartridges per the manufacturer, recharge the softener with salt, and test the treated water after service.

Pipe expansion: PEX and CPVC expand with temperature; install expansion loops or offsets, and do not trap the pipe in a tight hole; the expansion rate for PEX is about 1 in. per 100 ft per 10°F.

Freeze protection: a pipe in an unheated space needs insulation and heat tape; a freeze-proof hydrant drains back after each use; a hose bibb should be shut off and drained in winter.

Water hammer: install an arrestor near the valve or appliance; size the arrestor to the system volume; secure loose pipe with hangers.

Noise: a noisy pipe can be caused by high velocity (above 8 fps), a loose washer, or a worn valve; a pressure-reducing valve reduces noise from high pressure.

Corrosion: dissimilar metals require a dielectric union; copper and steel must be separated; a stray current can cause electrolytic corrosion.

Thermal expansion: a closed system with a backflow preventer requires an expansion tank; the tank precharge is set to the static pressure.

Pipe support: support horizontal pipe at the code's spacing; support vertical pipe at each floor; allow for expansion at the hangers with a roller or a slide.

Testing: after installation, flush the system, test for leaks, and verify the pressure and temperature at the fixtures; document the test results.