Red Seal Plumber cheat sheet

Fixture unit method: assign each fixture a demand in fixture units (FU), sum by type (private vs public), then read the supply pipe size from the appropriate fixture-unit table; 1 FU ≈ 1 gpm (0.06 L/s) of demand for sizing purposes.

Minimum fixture flow/pressure: water closets typically require 8 psi (55 kPa) flowing at the fixture; most fixtures are rated at 20 psi (140 kPa) minimum flowing pressure unless the manufacturer states otherwise.

Developed length: measure the longest run from the water meter or source to the farthest fixture, then add allowances for fittings and valves; pipe sizing tables are indexed by developed length and elevation difference.

Slope rules: horizontal drainage pipe 3 in (75 mm) and smaller slopes at 1/4 in per ft (2%); 4 in (100 mm) and larger may slope at 1/8 in per ft (1%). Vent piping must slope back toward the drain.

Trap arm limits: a trap arm may not change direction more than once before the vent, and its length is limited by pipe size (e.g., 1-1/4 in trap arm ≤ 5 ft/1.5 m; 1-1/2 in ≤ 6 ft/1.8 m; 2 in ≤ 8 ft/2.4 m under many codes).

Vent sizing: a vent stack serving a building drain carries air, not water; each fixture's vent must be at least half the diameter of its drain (never less than 1-1/4 in/32 mm), and vents must rise at least 6 in (150 mm) above the flood-level rim of the highest served fixture.

Water test: the water distribution system is hydrostatically tested at not less than the working pressure, typically 100 psi (690 kPa) for at least 60 minutes with no drop in pressure.

Drainage test: DWV systems are tested with water to a 10 ft (3 m) head for 15 minutes, or with air at 5 psi (35 kPa) for 15 minutes; test plugs must be removed and traps refilled after testing.

Backflow protection: an air gap is the preferred protection; a reduced-pressure zone (RPZ) assembly is required for high-hazard connections, and a double check valve for low-hazard connections; test annually and record results.

Water heater relief valve: the T&P relief valve must be rated at or below the heater's maximum working pressure, its discharge must terminate within 6 in (150 mm) of the floor or outside, and the discharge pipe must not be trapped or reduced.

Expansion control: a closed water system needs a thermal expansion tank sized to the system volume and temperature rise; a check valve or backflow preventer makes a system closed.

Gas piping pressure test: a test at 1-1/2 times the working pressure or at least 3 psi (20 kPa) for 10 minutes is common for low-pressure systems; use a manometer or calibrated gauge and record the result.

Combustion air: a confined space needs two permanent openings, one near the top and one near the bottom, each sized per the code (e.g., 1 in² per 1,000 Btu/h of input when using interior air with a volume allowance).

Drain cleaning: a cable or auger is sized to the pipe (e.g., 5/16 in cable for 1-1/4 to 2 in lines, 3/8 in for 2 to 3 in, 1/2 in for 3 to 4 in); never force a head through a trap.

Leak detection: pressurize with air and use soap solution on joints, or isolate sections with test plugs; a pressure drop on a gauge indicates a leak even when water is not visible.

Fixture servicing: replace a failed flush valve diaphragm or flapper before replacing the whole valve; check the refill tube and overflow for continuous running.

Water quality: flush new piping and test for chlorine residual or bacteria after repairs; a cross-connection or backflow event requires disinfection and retesting.

Plan reading: identify the building drain (lowest horizontal), building sewer, soil stack, waste stack, vent stack, and stack vent; the stack vent is the continuation of the soil or waste stack above the highest fixture.

Fixture spacing: water closets must be at least 15 in (380 mm) from centerline to side wall and 30 in (760 mm) centerline to centerline; a 30 in clear space in front of the fixture is typical.

Pipe support: horizontal cast iron pipe is supported at intervals of not more than 5 ft (1.5 m) for 2 in and smaller, and 10 ft (3 m) for larger sizes; plastic pipe support intervals vary by manufacturer and temperature.

Code hierarchy: the local authority having jurisdiction (AHJ) adopts a model code (e.g., National Plumbing Code of Canada, IPC, UPC); the most restrictive applicable requirement governs when documents conflict.

Materials: no lead content in potable water pipe, solder, or flux; lead-free is defined as ≤ 0.25% weighted average lead content in wetted surfaces.

Isolation: each fixture or fixture group needs a accessible shutoff valve; the main shutoff must be accessible and clearly identified.

Sizing by fixture count: a 3/4 in (20 mm) service can typically serve a small dwelling; larger buildings require a meter and service sized from the total fixture-unit load and the pressure available.

Permits and inspections: work must be inspected before concealment (rough-in) and after final connections; pressure tests are witnessed and recorded before the system is covered.

Drainage fixture units (DFU): a water closet = 4 DFU (private) or 6 DFU (public); a lavatory = 1 DFU; a bathtub or shower = 2 DFU; a kitchen sink = 2 DFU; a floor drain = 1 DFU.

Stack sizing: a 3 in (75 mm) soil stack can serve up to about 24 DFU on one branch; a 4 in (100 mm) stack serves much more - always confirm against the adopted code table because limits differ.

Trap seal: the trap seal depth is 2 to 4 in (50 to 100 mm); a trap must be protected by a vent to prevent siphonage.

Cleanouts: required at the base of each stack, at the building sewer, at changes of direction greater than 45 degrees, and at intervals not exceeding 100 ft (30 m) in horizontal runs.

Water hammer: arrestors are installed near quick-closing valves and sized to the system; a pressure-reducing valve is set to about 50-60 psi (345-415 kPa) on high-pressure systems.

Hot water temperature: storage at 140°F (60°C) to control Legionella, then temper to 120°F (49°C) at the fixture with a mixing valve; a scald-prevention limit applies at fixtures used by children or the elderly.

Rainwater and storm drainage: roof drains and leaders are sized by rainfall intensity and roof area; they must not connect to the sanitary drainage system unless the code allows it.

Cross-connection control: an air gap of at least twice the effective opening of the supply pipe is required for a receiving vessel; a hose bibb needs a vacuum breaker.

Pump sizing: total dynamic head = static lift + friction loss + discharge pressure; flow must meet peak demand; a booster pump is selected from the pump curve at the design flow.

Sump and sewage pumps: a check valve and a union are installed on the discharge; the pit must be vented, and the pump must be sized for the vertical lift plus friction.

Water pressure: static pressure at the highest fixture should be at least 20 psi (140 kPa) for most fixtures; excessive pressure (above 80 psi/550 kPa) requires a pressure-reducing valve.

Insulation: hot water lines are insulated to reduce heat loss; cold lines are insulated to prevent condensation; pipe insulation must be protected from UV and physical damage.

Frozen pipe prevention: pipes in exterior walls need heat tracing or insulation; a freeze event requires thawing from the open end toward the frozen section, never with an open flame.

Testing after repair: isolate the repaired section, refill, and pressure test; check for leaks at joints and confirm fixture operation before returning to service.

Maintenance records: log pressure tests, backflow tests, and pump run times; a failing pump curve or rising run time indicates wear and triggers servicing.

Ventilation: a plumbing stack must terminate outdoors above the roof; a vent must not terminate under a window or near an air intake.

Joining methods: copper can be soldered (lead-free solder), brazed, or press-fitted; PEX uses crimp, clamp, or expansion fittings; CPVC uses solvent cement; each method has its own pressure and temperature rating.

Dissimilar metals: dielectric unions or insulating bushings are required between copper and steel to prevent galvanic corrosion.

Pipe expansion: plastic pipe expands with temperature; install expansion loops or offsets, and do not anchor rigidly between fixed points.

Valve types: gate and ball valves for isolation, globe and needle valves for throttling, check valves for one-way flow, and pressure-reducing valves for regulating downstream pressure.

Water meter: the meter must be installed with a strainer, a bypass where required, and a shutoff on each side; the meter is tested for accuracy and read at the service connection.

Backflow assembly testing: an RPZ is tested with a differential pressure gauge; the relief valve opening point and check valve differentials must be within the manufacturer's limits.

Fire protection: standpipes and sprinkler systems are separate from the potable system; a fire line needs a backflow preventer and a flow test.

Commissioning: flush the system, test pressure, check fixture flow rates against design, and record results before handover.

Building sewer: the pipe from the building drain to the public sewer or private disposal; it must have a cleanout at the building and at intervals, and slope at 1/4 in per ft (2%) for 4 in and smaller.

Septic systems: a septic tank is sized by bedroom count (e.g., 1,000 to 1,500 gallons for a typical dwelling); the drain field is sized by soil percolation rate and daily flow.

Grease interceptors: required for commercial kitchens; sized by fixture units and flow, and must be cleaned at the frequency set by the AHJ.

Storm drainage: roof area × rainfall intensity gives the design flow; leaders and gutters are sized from that flow, and downspouts must not discharge onto a neighbor's property.

Water service: the service line is sized from the fixture-unit load and the pressure at the main; a meter and a main shutoff are required at the property line or building entry.

Testing the sewer: a water test or air test is performed before backfill; the sewer must pass a leakage test and be inspected by the AHJ.

Sewer gas: traps and vents prevent sewer gas from entering the building; a dry trap allows gas to pass, so floor drains need trap primers.

Site plan: locate the sewer, water service, and any septic field relative to the building and property lines; setbacks are set by the local code.

Occupancy and fixtures: fixture counts are based on occupancy type and occupant load (e.g., one water closet per 25 occupants for some assembly occupancies); confirm against the adopted code.

Accessibility: an accessible water closet needs a 60 in (1,525 mm) clear turning space, grab bars, and a seat height of 17 to 19 in (430 to 485 mm); lavatories need knee clearance and insulated pipes.

Pipe sizing for buildings: use the fixture-unit method with the Hunter curves or the code tables; account for flush valve fixtures separately because they have higher peak demand.

Water supply design: peak demand is estimated from fixture units; the pipe size is chosen so velocity stays below about 8 ft/s (2.4 m/s) in supply lines to limit noise and erosion.

Drainage design: stack sizing depends on the number of fixture units and the stack height; an oversized stack can cause poor scouring, and an undersized stack causes backup.

Venting: a vent system must equalize pressure; a common vent can serve two fixtures, but the fixtures must be at the same level and the vent sized for the combined load.

Fire stopping: penetrations through fire-rated assemblies must be sealed with an approved firestop system; plastic pipe penetrations need special firestop devices.

Inspection sequence: rough-in inspection before covering, then final inspection after fixtures and trim are installed and tested.

Water heater installation: the heater needs a seismic strap where required, a drain pan with a discharge to a safe location, and a T&P relief valve piped to within 6 in (150 mm) of the floor.

Gas connection: use a listed connector, a sediment trap, and a shutoff valve within 6 ft (1.8 m) of the appliance; test the connection with soap solution.

Venting: a gas water heater needs a flue sized to the appliance and a draft hood; a blocked flue causes carbon monoxide, so test draft after installation.

Electrical: a water heater on a dedicated circuit needs a disconnect within sight; check the element and thermostat before replacing the heater.

Fixture installation: set the water closet on a new wax ring, level the bowl, and tighten bolts evenly to avoid cracking the porcelain.

Testing: fill the system, check for leaks at all joints, and operate every fixture; record the pressure test result and the date.

Maintenance: flush the water heater annually to remove sediment; replace the anode rod when it is consumed to extend tank life.

Documentation: provide the owner with the manufacturer's instructions, warranty information, and the test records for the installation.

Safety: lock out and tag out before servicing; use PPE (gloves, eye protection), and ventilate the area when using solvent cement or gas.

Confined space: a sewer or pit entry requires atmospheric testing, a attendant, and a rescue plan; never enter alone.

Hot work: a soldering or brazing permit may be required; keep a fire extinguisher nearby and protect combustible surfaces.

Code updates: the AHJ adopts code editions; check the effective edition and local amendments before designing or installing.

Estimating: take off pipe lengths, fittings, and fixtures from the drawings, add waste allowance, and price labour by the hour or by the fixture.

Project scheduling: sequence rough-in, inspection, and finish work; coordinate with other trades so the plumbing is not covered before inspection.

Quality control: check slope, support, and joint tightness before concealment; a re-inspection costs time, so verify first.

Customer communication: explain the scope, the test results, and any code-required upgrades before starting work.

Pipe sizing formula: flow (gpm) = area (ft²) × velocity (ft/s) × 448.8; use it to check that the selected pipe size meets the design flow at an acceptable velocity.

Pressure loss: friction loss in a pipe increases with flow and decreases with diameter; the Hazen-Williams equation is used for water lines, and equivalent length converts fittings to pipe length.

Fixture unit conversion: 1 fixture unit ≈ 1 gpm (0.06 L/s) of demand; a flush valve water closet counts as 4 to 6 DFU depending on public or private use.

Static head: pressure gain or loss = 0.433 psi per ft of elevation (9.8 kPa per m); a 10 ft rise drops pressure by about 4.3 psi.

Drainage capacity: the capacity of a horizontal drain depends on slope and diameter; a 4 in pipe at 1/4 in per ft carries far more than a 3 in pipe at the same slope.

Vent sizing: a vent must be at least half the drain diameter and never smaller than 1-1/4 in (32 mm); a stack vent is sized from the total fixture units.

Water heater sizing: first-hour rating must meet peak demand; recovery rate = input (Btu/h) ÷ (8.33 × temperature rise).

Test pressure: a hydrostatic test is typically 100 psi (690 kPa) for 60 minutes; a drainage test uses a 10 ft (3 m) head for 15 minutes.

Backflow prevention: an air gap provides the highest protection; an RPZ is used for high hazard; a double check valve for low hazard; a vacuum breaker for hose connections.

Cross-connection survey: identify all connections to the potable system, including irrigation, boilers, and chemical lines, and protect each one.

Testing frequency: backflow assemblies are tested at installation and annually; the test report goes to the water authority.

Water quality testing: test for chlorine residual, turbidity, and bacteria after repairs or a main break; flush until results are within limits.

Disinfection: new or repaired potable water lines are disinfected with a chlorine solution (e.g., 50 ppm for 24 hours) and flushed before use.

Lead: older buildings may have lead service lines or lead solder; test the water and replace lead components.

Legionella: control by keeping hot water at 140°F (60°C) in storage and circulating it; dead legs and stagnant lines increase risk.

Records: keep test results, disinfection records, and maintenance logs for the AHJ and the building owner.

Rough-in dimensions: set the water closet flange at 12 in (305 mm) from the finished wall for a standard toilet; confirm the rough-in of the fixture before installing the flange.

Drain height: a shower drain is set below the finished floor by the thickness of the pan; a bathtub drain is set at the manufacturer's dimension.

Vent height: a vent must rise at least 6 in (150 mm) above the flood-level rim of the highest fixture before offsetting horizontally.

Pipe support spacing: support plastic pipe at intervals set by the manufacturer (often 3 ft/0.9 m for 1/2 in PEX); support copper at 6 ft (1.8 m) for horizontal runs.

Sleeves and penetrations: a pipe passing through a foundation needs a sleeve and flexible seal; a pipe through a fire wall needs a firestop.

Freeze protection: slope exterior pipes to drain, install frost-proof hydrants, and insulate or heat-trace exposed lines.

Noise control: use insulated pipe or cast iron for stacks near bedrooms to reduce flow noise.

Final inspection: verify fixture operation, check for leaks, and confirm the test records before the system is signed off.

Water service sizing: the service must supply the peak demand at the minimum residual pressure; a 1 in (25 mm) service is common for a large dwelling, and a 3/4 in (20 mm) for a small one.

Meter sizing: the meter is selected from the peak flow and the pressure loss allowed; an undersized meter causes low pressure at fixtures.

Pressure-reducing valve: set to 50-60 psi (345-415 kPa) when the supply exceeds 80 psi (550 kPa); install a strainer and a bypass where required.

Water hammer arrestor: install near quick-closing valves; size by fixture units served.

Pipe insulation: insulate hot lines to reduce heat loss and cold lines to prevent condensation; protect exterior insulation from UV.

Thermal expansion: a closed system needs an expansion tank; size by system volume and temperature rise.

Testing: hydrostatic test at 100 psi (690 kPa) for 60 minutes; record the result before covering the pipe.

Maintenance: check the PRV, expansion tank, and relief valve annually; replace a failed relief valve, never plug it.

Drain cleaning tools: use a cable sized to the pipe; a 5/16 in cable for 1-1/4 to 2 in lines, 3/8 in for 2 to 3 in, and 1/2 in for 3 to 4 in.

Jetting: use a jetter for grease and roots in larger lines; the pressure and nozzle are selected for the pipe size and condition.

Camera inspection: a camera locates breaks, roots, and bellies; record the distance and depth for the repair.

Leak repair: cut out the damaged section, install a coupling or repair clamp, and pressure test the repair before backfilling.

Valve repair: replace a washer or cartridge before replacing the whole valve; check the seat for damage.

Toilet repair: replace the flapper or fill valve when the toilet runs continuously; check the refill tube and the overflow height.

Water heater service: flush sediment annually and replace the anode rod when consumed; a leaking tank is replaced, not repaired.

Test after repair: refill, pressure test, and operate the fixture; record the result and any parts replaced.

Code adoption: the AHJ adopts a model code and local amendments; the most restrictive requirement governs when documents conflict.

Permits: a permit is required for new work, alterations, and fixture replacement in most jurisdictions; work without a permit may be ordered removed.

Inspections: rough-in inspection before concealment, and final inspection after fixtures and trim are installed.

Testing: the AHJ may witness the pressure test; record the pressure, duration, and result.

Materials: use listed and labelled materials; lead-free solder and flux are required for potable water.

Accessibility: accessible fixtures need clear space, grab bars, and insulated pipes; confirm the local accessibility standard.

Fire stopping: penetrations through fire-rated assemblies need an approved firestop system.

Documentation: provide as-built drawings, test records, and maintenance information to the owner.

Water heater types: storage tank, tankless, and heat pump water heaters; each has different venting, electrical, and space requirements.

Tankless sizing: size by the peak flow and temperature rise; a tankless unit may not supply multiple fixtures at once if undersized.

Heat pump water heater: needs air space and condensate drainage; it cools the surrounding space.

Solar hot water: a closed loop with a heat exchanger and a pump; the collector must be protected from freezing.

Recirculation: a hot water recirculation loop reduces wait time but increases energy use; insulate the loop and use a timer or demand control.

Temperature control: a thermostatic mixing valve at the heater outlet limits scald risk; set storage at 140°F (60°C) and temper to 120°F (49°C).

Venting: a gas appliance needs a correctly sized flue and a draft test; a blocked flue causes carbon monoxide.

Maintenance: flush the tank, check the anode rod, and test the T&P relief valve annually.

Fixture units: a lavatory = 1 DFU, a water closet = 4 DFU (private), a bathtub = 2 DFU, a kitchen sink = 2 DFU, a floor drain = 1 DFU.

Stack sizing: a 3 in (75 mm) stack serves about 24 DFU on one branch; confirm against the code table.

Trap arm: the trap arm length is limited by pipe size; a 1-1/2 in trap arm is limited to about 6 ft (1.8 m).

Cleanouts: required at the base of each stack and at changes of direction greater than 45 degrees, and at intervals not exceeding 100 ft (30 m).

Vent termination: a vent must terminate outdoors above the roof and away from windows and air intakes.

Slope: 1/4 in per ft (2%) for 3 in and smaller; 1/8 in per ft (1%) for 4 in and larger.

Backwater valve: install on the building sewer where backflow from the public sewer is possible; it must be accessible for maintenance.

Testing: water test to a 10 ft (3 m) head for 15 minutes, or air test at 5 psi (35 kPa) for 15 minutes.

Pipe materials: copper for potable water, PVC for drainage, CPVC for hot water, PEX for flexible supply, and cast iron for noise reduction.

Joining: solder copper with lead-free solder; solvent-cement PVC and CPVC; crimp or expand PEX; thread steel with pipe dope or tape.

Dissimilar metals: use dielectric unions between copper and steel to prevent galvanic corrosion.

Support: support horizontal pipe at intervals set by the code or manufacturer; support vertical stacks at each floor.

Expansion: plastic pipe expands with temperature; install expansion loops or offsets.

Protection: sleeve pipes through masonry and concrete; protect plastic pipe from UV and physical damage.

Testing: pressure test the system before concealment; check all joints with soap solution or a gauge.

Documentation: record the materials used and the test results for the owner and the AHJ.

Pump sizing: total dynamic head = static lift + friction loss + discharge pressure; select the pump from its curve at the design flow.

Sump pump: install a check valve and a union on the discharge; the pit must be vented and the pump sized for the lift.

Booster pump: needed when the supply pressure is insufficient; size by peak demand and the required residual pressure.

Pressure tank: a bladder tank maintains pressure and reduces pump cycling; size by pump flow and the acceptable cycle time.

Controls: a pressure switch starts and stops the pump; set the cut-in and cut-out pressures to match the system.

Maintenance: check the pump run time and the pressure tank precharge; a rising run time indicates wear.

Testing: run the pump, check the flow and pressure, and verify the check valve holds.

Records: log pump run times and maintenance for the owner.

Gas pipe sizing: size by the total Btu/h input and the length of the run; use the code table for the gas type and pressure.

Gas pressure test: test at 1-1/2 times the working pressure or at least 3 psi (20 kPa) for 10 minutes; record the result.

Sediment trap: install a dirt leg at each appliance to catch debris before it reaches the controls.

Connector: use a listed connector and a shutoff valve within 6 ft (1.8 m) of the appliance.

Combustion air: a confined space needs two openings sized per the code; a direct-vent appliance draws air from outside.

Venting: size the flue to the appliance and test the draft after installation.

Leak detection: use soap solution on joints; never use a flame to test for gas leaks.

Safety: if a gas leak is suspected, shut off the gas, ventilate, and call the utility; do not operate electrical switches.

Fixture flow rates: a lavatory aerator is often 1.5 gpm (5.7 L/min), a showerhead 2.5 gpm (9.5 L/min), and a water closet 1.28 gal (4.8 L) per flush under current standards.

Pressure: most fixtures need at least 20 psi (140 kPa) flowing pressure; a flush valve water closet needs about 25 psi (170 kPa).

Temperature: hot water at the fixture should not exceed 120°F (49°C) for scald prevention; storage is kept at 140°F (60°C).

Accessibility: an accessible lavatory needs knee clearance and insulated pipes; a water closet needs grab bars and a 60 in (1,525 mm) turning space.

Installation: set fixtures level, seal with caulk or a gasket, and connect the trap and supply.

Testing: operate each fixture and check for leaks at the supply, drain, and trap.

Maintenance: replace a worn cartridge or flapper before replacing the fixture.

Documentation: provide the manufacturer's instructions and warranty to the owner.

Storm drainage: roof area × rainfall intensity gives the design flow; size the leaders and gutters from that flow.

Roof drain: a roof drain needs a strainer and a flashing; the leader must discharge to a storm sewer or a safe location.

Sump: a sump pit collects groundwater; the pump discharges to a safe location and must not connect to the sanitary sewer unless allowed.

Backwater valve: install on the building sewer where backflow is possible; it must be accessible.

Foundation drainage: a weeping tile system collects water around the foundation and leads to a sump.

Testing: test the storm system with water before backfilling.

Maintenance: clean the roof drain strainer and the sump pit regularly.

Code: confirm the local rules for storm water discharge and connection.

Water quality: test for bacteria, chlorine residual, and turbidity after repairs; flush until results are within limits.

Disinfection: new or repaired potable lines are disinfected with a chlorine solution and flushed before use.

Lead: older buildings may have lead service lines or solder; test the water and replace lead components.

Legionella: keep hot water at 140°F (60°C) in storage and circulate it; avoid dead legs and stagnant lines.

Cross-connection: protect every connection to the potable system with an air gap, RPZ, or vacuum breaker.

Testing: backflow assemblies are tested annually; record the results for the water authority.

Records: keep test results, disinfection records, and maintenance logs.

Reporting: a contamination event must be reported to the AHJ and the water utility.

Fire stopping: penetrations through fire-rated assemblies need an approved firestop system; plastic pipe needs a special firestop device.

Sleeves: a pipe through a foundation needs a sleeve and a flexible seal; a pipe through a fire wall needs a firestop.

Support: support horizontal pipe at intervals set by the code; support vertical stacks at each floor.

Expansion: plastic pipe expands with temperature; install expansion loops or offsets.

Freeze protection: slope exterior pipes to drain and install frost-proof hydrants.

Noise: use insulated pipe or cast iron for stacks near bedrooms.

Testing: pressure test before concealment and record the result.

Inspection: the AHJ inspects the rough-in before the pipe is covered.

Estimating: take off pipe lengths, fittings, and fixtures from the drawings, add a waste allowance, and price labour by the hour or by the fixture.

Scheduling: sequence rough-in, inspection, and finish work; coordinate with other trades so the plumbing is not covered before inspection.

Quality control: check slope, support, and joint tightness before concealment; a re-inspection costs time.

Customer communication: explain the scope, the test results, and any code-required upgrades before starting work.

Safety: lock out and tag out before servicing; use PPE and ventilate the area when using solvent cement or gas.

Confined space: a sewer or pit entry requires atmospheric testing, an attendant, and a rescue plan.

Hot work: a soldering or brazing permit may be required; keep a fire extinguisher nearby.

Documentation: provide as-built drawings, test records, and maintenance information to the owner.

Trap seal: the trap seal depth is 2 to 4 in (50 to 100 mm); a trap must be protected by a vent to prevent siphonage.

Trap arm: the trap arm may not change direction more than once before the vent, and its length is limited by pipe size.

Vent: a vent must rise at least 6 in (150 mm) above the flood-level rim of the highest fixture before offsetting horizontally.

Stack vent: the stack vent is the continuation of the soil or waste stack above the highest fixture.

Common vent: a common vent can serve two fixtures at the same level; size it for the combined load.

Air admittance valve: an AAV admits air but does not vent sewer gas; it must be installed where the code allows.

Testing: the vent system is tested with the drainage system; check for blockages and proper slope.

Maintenance: keep vents clear of nests and debris; a blocked vent causes gurgling and slow drains.

Water heater relief valve: the T&P relief valve must be rated at or below the heater's maximum working pressure; its discharge must terminate within 6 in (150 mm) of the floor or outside.

Expansion control: a closed system needs a thermal expansion tank sized to the system volume and temperature rise.

Seismic: a water heater needs a seismic strap where required by the code.

Drain pan: a water heater in a location where leakage could cause damage needs a drain pan with a discharge to a safe location.

Venting: a gas water heater needs a correctly sized flue and a draft test after installation.

Electrical: a water heater on a dedicated circuit needs a disconnect within sight.

Maintenance: flush the tank annually and replace the anode rod when consumed.

Testing: test the T&P relief valve annually and record the result.

Water test: the distribution system is hydrostatically tested at not less than the working pressure, typically 100 psi (690 kPa) for 60 minutes with no drop.

Drainage test: test with water to a 10 ft (3 m) head for 15 minutes, or with air at 5 psi (35 kPa) for 15 minutes.

Gas test: test at 1-1/2 times the working pressure or at least 3 psi (20 kPa) for 10 minutes.

Backflow test: an RPZ is tested with a differential pressure gauge; the relief valve opening point and check valve differentials must be within limits.

Leak detection: use soap solution on joints or a pressure gauge; a pressure drop indicates a leak.

Record: record the pressure, duration, and result for the AHJ and the owner.

Repair: after a failed test, locate and repair the leak, then retest the entire section.

Safety: never test with a flame or with air on a system not designed for it.

Plan reading: identify the building drain, building sewer, soil stack, waste stack, vent stack, and stack vent on the drawings.

Fixture spacing: a water closet needs at least 15 in (380 mm) from centerline to side wall and 30 in (760 mm) centerline to centerline.

Pipe support: support horizontal cast iron at 5 ft (1.5 m) for 2 in and smaller, and 10 ft (3 m) for larger sizes.

Code hierarchy: the AHJ adopts a model code; the most restrictive requirement governs when documents conflict.

Materials: no lead in potable water pipe, solder, or flux; lead-free is ≤ 0.25% weighted average lead content.

Isolation: each fixture or fixture group needs an accessible shutoff valve; the main shutoff must be accessible and identified.

Sizing: a 3/4 in (20 mm) service can serve a small dwelling; larger buildings need a meter and a service sized from the fixture-unit load.

Permits: work must be inspected before concealment and after final connections.

Drain cleaning: use a cable sized to the pipe; a 5/16 in cable for 1-1/4 to 2 in lines, 3/8 in for 2 to 3 in, and 1/2 in for 3 to 4 in.

Jetting: use a jetter for grease and roots in larger lines; select the pressure and nozzle for the pipe size.

Camera: a camera locates breaks, roots, and bellies; record the distance and depth for the repair.

Leak repair: cut out the damaged section, install a coupling or repair clamp, and pressure test the repair.

Valve repair: replace a washer or cartridge before replacing the whole valve; check the seat for damage.

Toilet repair: replace the flapper or fill valve when the toilet runs continuously.

Water heater service: flush sediment annually and replace the anode rod when consumed.

Test after repair: refill, pressure test, and operate the fixture; record the result.

Occupancy: fixture counts are based on occupancy type and occupant load; confirm against the adopted code.

Accessibility: an accessible water closet needs a 60 in (1,525 mm) turning space, grab bars, and a seat height of 17 to 19 in (430 to 485 mm).

Pipe sizing: use the fixture-unit method with the code tables; account for flush valve fixtures separately.

Velocity: keep supply velocity below about 8 ft/s (2.4 m/s) to limit noise and erosion.

Stack sizing: stack size depends on the fixture units and the stack height; an oversized stack can cause poor scouring.

Venting: a vent system must equalize pressure; a common vent can serve two fixtures at the same level.

Fire stopping: penetrations through fire-rated assemblies need an approved firestop system.

Inspection: rough-in inspection before covering, then final inspection after fixtures and trim are installed.