These are plain-English summaries for quick recall — not code text. Plumbing rules differ between the International Plumbing Code (IPC) and the Uniform Plumbing Code (UPC), and local amendments and AHJ requirements vary and change. Always verify against the plumbing code currently adopted in your jurisdiction.
This is a comprehensive plain-English index to the plumbing provisions trades look up most — from traps, venting, and drain slope to water-supply sizing, water heaters, backflow protection, cleanouts, fixtures, and gas-piping basics. Search by keyword, tap a popular lookup, or filter by category to jump to the plain-English summary and the rule-of-thumb you actually use in the field. Where the IPC and UPC differ, the common value is noted — always confirm the exact number against your adopted code and local AHJ.
Permits and approved plans
Most plumbing work beyond a like-for-like fixture swap needs a permit and inspection, and the work has to follow the plans the AHJ approved.
Approved and listed materials
Pipe, fittings, and devices must be listed to a recognized standard and marked so an inspector can confirm they are approved for the use.
Protection of pipes
Piping run through framing or where it could be struck by a nail or screw needs protection such as steel nail plates, and pipe through concrete or corrosive areas needs sleeving or wrapping.
Protection from freezing
Water pipe cannot be run where it will freeze – keep it out of exterior walls and unconditioned space, or insulate and provide heat.
Condensate disposal
Condensate from AC coils and high-efficiency appliances must drain to an approved point, never onto the ground where it causes damage or into the sanitary system without an air gap.
Piping support and hangers
Piping must be supported at intervals and with hangers that will not damage the pipe, so it cannot sag, lean on the fixture, or stress joints.
Trenching and backfill
Underground piping needs firm, continuous support in the trench and backfill that will not damage or crush it.
Cutting and notching structure
Holes and notches in joists and studs for piping are limited so you do not weaken the framing.
Workmanlike installation
Plumbing has to be installed in a neat, workmanlike manner with proper alignment, support, and no defective material.
Independent fixture connections
Each fixture drain and supply generally connects so it can be maintained without disturbing others, with accessible shutoffs and unions where needed.
IPC vs UPC – know which you are on
Jurisdictions adopt either the International Plumbing Code, the Uniform Plumbing Code, or a state-amended version – the two differ on venting, sizing, and materials.
Definitions drive the rules
Terms like fixture unit, developed length, branch, stack, and building drain have exact code meanings that change how a rule applies.
Minimum required fixtures
The number of water closets, lavatories, and other fixtures required is set by the building occupancy and its load, using the code fixture-count tables.
Fixture setting and joints
Fixtures must be set level, secured, and sealed to the wall or floor so waste cannot leak behind or under them.
Drinking fountains
Drinking fountains and bottle fillers are required in many occupancies and must be protected from contamination.
Urinals
Urinals have their own flush, trap, and cleaning requirements and count toward the fixture totals for the occupancy.
Faucet and fixture fittings
Fixture fittings must be listed, limit flow to the code maximum, and for certain fixtures limit temperature to prevent scald.
Whirlpool and bathtubs
Whirlpool tubs need an accessible pump, an accessible drain, and proper bonding of metal parts.
What a fixture unit is
A fixture unit is a load value assigned to each fixture – drainage fixture units (DFU) for waste and water supply fixture units (WSFU) for supply – used to size pipe.
Common drainage fixture units
Typical DFU values are around 1 for a lavatory, 2 for a bathtub, shower, or kitchen sink, and 3 to 4 for a private water closet depending on flush volume.
Common water supply fixture units
WSFU values differ for private versus public use and for flush-tank versus flushometer fixtures, then total load is converted to gpm demand.
Accessible (ADA) fixtures – basics
Where accessibility applies, fixtures need specific mounting heights, clearances, and controls, and this is coordinated with the accessibility standard, not just the plumbing code.
Accessible lavatory clearances
An accessible lavatory needs knee and toe clearance underneath and insulated or protected hot and drain piping so a user is not burned.
Accessible water closet
An accessible water closet has a defined centerline from the side wall, clear floor space, and grab-bar backing – coordinate rough-in early.
Floor drains as fixtures
Floor drains and floor sinks are fixtures too – they need a trap, a trap seal (often a primer), and a drainage connection.
Food-waste (garbage) disposers
Disposers need adequate drain size and water supply and generally cannot discharge through an undersized or S-trapped line.
Clothes washer standpipe
A clothes washer drains into a trapped, vented standpipe of the right height so it does not overflow or siphon.
Showers – waterproofing and drains
Shower floors need a sloped, watertight receptor and a listed drain with a weep or bonding flange to move water that gets under the finish.
Scald protection at showers/tubs
Shower and tub-shower valves generally must be pressure-balanced or thermostatic and limited to a maximum outlet temperature to prevent scalding.
Water closet flush volume
Water closets are limited to a maximum flush volume, and dual-flush and low-flow models are common – this affects the DFU you assign.
Sizing the distribution system
Supply piping is sized from total WSFU converted to demand in gpm, the available pressure, and the developed length and fittings, so every fixture gets adequate flow.
Minimum flow pressure at fixtures
Each fixture type has a minimum flowing pressure it needs to work; flushometers need more than flush-tank fixtures.
Maximum static pressure – 80 psi
When static water pressure exceeds about 80 psi, an approved pressure-reducing valve is required to protect the system.
Water velocity limits
Piping is sized to keep water velocity in a reasonable range so you avoid noise, erosion, and water hammer.
Shutoff valves
The system needs a main shutoff, and fixtures and appliances need accessible individual stops so one can be isolated without killing the whole building.
Water service and main valve
The building water service needs an accessible shutoff near the entry, and the meter and any backflow assembly must be accessible.
Hot water distribution
A hot water supply is required to fixtures that need it, delivered at a usable temperature, with hot on the left at fixtures.
Hot water temperature maintenance
Long hot-water runs or recirculation systems are used so users get hot water without wasting a lot of standing water.
Hose bibb backflow protection
Outdoor sillcocks and hose connections need a listed vacuum breaker so a hose cannot siphon dirty water back into the potable supply.
Water hammer arrestors
Quick-closing valves such as washing-machine and dishwasher solenoids need listed water-hammer arrestors, not just a capped air chamber.
Approved supply materials
Water distribution uses listed materials such as copper, PEX, CPVC, and PE-RT, each with its own fittings and limits – PVC is generally not for hot pressurized water.
PEX installation basics
PEX must use listed fittings, be protected from UV and certain chemicals, and be supported and sleeved where it passes through framing or slab.
Water service pipe size and separation
The building water service has a minimum size and must keep required separation from the sewer in a shared trench.
Burial depth below frost
Underground water piping needs cover deep enough to stay below the local frost line.
Thermal expansion control
On a closed system (check valve, PRV, or backflow preventer on the service), a thermal expansion tank or device is required to absorb pressure from heated water.
Potable water protection – general
The potable system must be protected at every point it could connect to a non-potable source, using an air gap or listed backflow assembly.
Disinfection of new piping
New or repaired potable water piping generally must be flushed and disinfected before use.
Valve accessibility and identification
Required valves must stay accessible and, for larger systems, be identified so the right valve is found fast.
Developed length and fitting loss
Sizing must account for the actual developed length of pipe plus the pressure lost through fittings, meters, and the backflow device.
Individual fixture supply size
Each fixture has a minimum supply branch size so it delivers rated flow.
Meter and backflow location
The water meter and any required backflow assembly need accessible, protected locations that allow testing and service.
Reduced-pressure zone on high hazard
Where a cross-connection is a high health hazard, a reduced-pressure principle (RPZ) assembly is generally required, not just a check valve.
T&P relief valve required
Every storage water heater needs a listed temperature-and-pressure relief valve to release if it overheats or over-pressurizes.
T&P discharge piping
The relief discharge line runs full-size, downhill, of approved material, to a safe point near the floor or an approved receptor, with the end open.
Water heater drain pan
Heaters where a leak would cause damage need a pan piped to an approved discharge point.
Seismic strapping
In seismic areas, tank water heaters generally must be strapped at two points (upper and lower third) to resist tipping – a UPC-region staple adopted widely.
Water heater as space heat / dual use
Using a water heater for both potable hot water and space heating has extra rules on materials and temperature – handle as a special system.
Water heater location and access
Heaters need accessible locations for service and, in garages, may need ignition-source elevation or listed flammable-vapor-ignition-resistant units.
Delivered hot water temperature
Hot water delivered to fixtures is commonly tempered near 120 F to limit scald risk, using a thermostatic mixing valve rather than just a low tank setting.
Combustion air for gas heaters
Gas water heaters need adequate combustion and ventilation air – this is governed by the fuel-gas / mechanical code, not the plumbing chapters.
Venting of gas water heaters
Atmospheric gas heaters need proper draft-hood venting and clearances; do not common-vent incompatible appliances.
Expansion control at the heater
On a closed system the heater sees pressure spikes when it fires, so a thermal expansion tank sized to the heater is required.
Separate temperature and pressure protection
Where a single combined T&P device is not used, separate listed temperature and pressure relief devices are required.
Listed and approved heaters
Water heaters must be listed and installed per the manufacturer instructions, which become part of the enforceable install.
Shutoff and unions at the heater
A heater needs an accessible cold-water shutoff and unions or flex connectors so it can be isolated and replaced.
Dielectric protection at connections
Where copper meets the steel tappings of a heater, dielectric unions or listed flex connectors slow galvanic corrosion.
Tankless water heater basics
Demand (tankless) heaters still need relief protection, proper gas or electrical supply, condensate handling on condensing units, and manufacturer venting.
Drain slope – small pipe
Horizontal drains 2-1/2 in and smaller are commonly sloped about 1/4 in per foot so waste flows by gravity.
Drain slope – larger pipe
Drains 3 in to 6 in are commonly sloped about 1/8 in per foot minimum; very large pipe can go flatter.
Too flat vs too steep
A drain that is too flat lets solids settle; one that is too steep can let liquid outrun solids and leave them behind.
Sizing drains by DFU
Building drains, branches, and stacks are sized from the total drainage fixture units they carry and their slope.
Building drain and sewer
The building drain collects the whole system and connects to the building sewer at the property; both are sized for the total DFU load and slope.
Changes of direction – fittings
Direction changes must use approved drainage fittings with proper sweep; sharp fittings such as short-radius turns are limited on the horizontal.
Horizontal to vertical vs horizontal to horizontal
Fitting choice depends on the direction change – what is allowed turning down into a stack is not the same as a flat turn on a drain.
Offsets in drainage stacks
Offsets in vertical stacks have rules on fittings and sometimes venting so flow is not disrupted and pressures stay controlled.
Stack sizing and fixture load
A stack cannot be smaller than the largest branch into it and is sized for total DFU and the number of stories it serves.
Do not reduce drain size downstream
Drain size cannot decrease in the direction of flow – it stays the same or gets larger.
Fixtures below sewer level
Fixtures below the level of the upstream sewer or curb generally must drain to a sump and be pumped up, not gravity-drained.
Backwater valves
Fixtures that sit below the next upstream manhole rim generally need a backwater valve so a surcharged main cannot back up into the building.
Cleanout access on drains
Drainage layout must include cleanouts so every part can be rodded – designed in, not added later.
Indirect waste – air gap or air break
Certain equipment (food, sterile, and some appliance drains) must discharge indirectly through an air gap or air break into a receptor, not connect directly.
Standpipe and receptor height
Indirect-waste standpipes and floor sinks have height and trap rules so they neither siphon nor overflow.
Approved joints in DWV
DWV joints must use approved methods for the material – solvent weld, gasket, hub-and-spigot, or no-hub bands – installed per the standard.
Prohibited fittings on drains
Fittings that obstruct flow, double hubs on drainage flow, and heel or side inlets used wrong are prohibited on drainage.
Future fixture rough-in
Roughed-in but unused drains still need proper size, trap provision, and a capped, accessible termination.
Dead ends prohibited
Drainage dead ends that collect waste are prohibited except where needed for an approved cleanout extension.
Drain pipe protection and support
DWV pipe needs the same support and protection as supply – proper hangers, nail plates, and sleeving through structure.
Building sewer size and slope
The building sewer to the main or septic is sized for total DFU and set at a slope that keeps it self-scouring.
Sewer and water separation
Where the building sewer and water service share a trench, code sets required horizontal separation and vertical offset to protect the potable line.
Why every trap is vented
Vents supply air to the drainage system so draining fixtures cannot siphon or blow out trap seals from pressure swings.
Trap-arm distance to vent
The horizontal run from a trap to its vent is limited, and the limit grows with pipe size; the arm must also not drop more than about one pipe diameter (IPC).
Trap-arm slope and total fall
On the IPC, the trap arm should not fall more than one pipe diameter between trap and vent so the trap does not lose its seal; UPC limits this differently.
Individual (fixture) vent
A dedicated vent serving one fixture connects at or above the trap arm and rises to tie into the vent system or roof.
Common vent
Two fixtures at the same level can share one vent when connected per the common-vent rules and sized for both.
Wet venting
In wet venting, an oversized drain from one or more fixtures also serves as the vent for others within a bathroom group, following strict layout and size limits.
Circuit venting
A row of fixtures on a horizontal branch can be circuit-vented with a vent taken off ahead of the last fixture, within the fixture-count limits.
Island (island fixture) venting
A sink with no wall behind it (kitchen island) uses a special looping island vent because a normal vertical vent is not possible.
Air admittance valves (AAV)
A listed AAV is a one-way mechanical vent that admits air but closes to gas; it is allowed only where the adopted code and AHJ permit, and it must stay accessible and in a ventilated space.
Vent termination height above roof
Vents through the roof must extend a minimum height above the roof surface so they cannot be blocked or flooded.
Vent termination near openings
Roof vents must stay a minimum distance from and above windows, doors, and air intakes so sewer gas does not drift back inside.
Frost-closure of vents
In cold climates vent terminals are increased in size or detailed so frost cannot close them off.
Vent grade and connection
Vents must rise and drain back by gravity to the drain they serve so condensate does not pool, and connect above the fixture flood level where required.
Vent connection above flood rim
Where a vent takes off from a drain it generally must rise above the flood-level rim of the fixture before running horizontal, so waste cannot enter the vent.
Vent sizing follows drain and length
Vent pipe size depends on the drain it protects and the developed length of the vent, not a guess.
Relief vents and yoke vents
Tall stacks and certain branch arrangements need relief or yoke vents to equalize pressure between the drainage and vent systems.
Vent stack and stack vent
A vent stack runs alongside a soil/waste stack to control pressures, while a stack vent is the dry extension of the stack above the top fixture.
Combination waste and vent
Flat, low fixtures such as floor sinks and island sinks can use an oversized combination waste-and-vent system where a normal vent is impractical.
Waste stack (single stack) venting
Some codes allow a single oversized stack to serve as both waste and vent under strict fixture and sizing limits.
No unvented traps (except allowed)
Every trap needs venting unless it is on a specifically listed system such as combination waste-and-vent – an unvented trap self-siphons.
Prohibited vent terminations
Vents cannot terminate under overhangs, near intakes, into other systems, or where they discharge onto walking surfaces.
Flat venting prohibited
A vent cannot run horizontal below the flood-level rim of the fixture it serves, because waste could flow into it.
Every fixture needs a trap
Each fixture that discharges wastewater needs a trap to hold a water seal that blocks sewer gas.
One trap per fixture
A fixture generally gets its own trap; you do not share one trap across fixtures except in specific listed assemblies (like a triple-bowl sink).
Trap seal depth 2 to 4 in
The standing water in a trap (the seal) is commonly kept about 2 to 4 in deep – enough to block gas, shallow enough to self-clean.
No S-traps
S-traps that drop straight into a vertical drain with no vent are prohibited because falling water siphons the seal dry.
Prohibited trap types
Bell traps, drum traps (except where allowed), full-S traps, crown-vented traps, and traps with moving parts are generally prohibited.
One trap per fixture, close to it
The trap must be close to the fixture outlet, with the vertical distance from the fixture to the trap weir limited so it does not lose its seal.
Trap size by fixture
Trap size follows the fixture: about 1-1/4 in for a lavatory, 1-1/2 in for sinks, tubs, and showers, and larger for floor drains, and a trap is never smaller than its drain.
Trap primers for floor drains
Floor drains that seldom see water dry out; a trap primer feeds them water periodically to keep the seal.
Trap seal loss and deep-seal traps
In hard-to-vent or high-evaporation spots, a deep-seal trap or a primer helps keep the seal intact.
Grease interceptors
Food-service operations need a grease interceptor sized to the flow so grease does not clog the sewer; it must be accessible for cleaning.
Oil and sand interceptors
Garages, shops, and car washes need oil/sand interceptors or separators to keep petroleum and grit out of the sanitary or storm system.
Interceptor venting and access
Interceptors and separators must be vented and left accessible for the routine cleaning they require.
Trap seal protection devices
Listed trap-seal protection devices (barrier or primer type) can protect floor-drain seals where allowed.
No trap downstream of a trap (double trapping)
A fixture cannot be double-trapped – two traps in series on one fixture trap air between them and block flow.
Cleanout at base of stack
A cleanout is generally provided at or near the foot of each vertical waste or soil stack for rodding.
Cleanout at direction changes
Cleanouts are required at significant changes of direction in the drain, where clogs most often catch.
Interval cleanouts on horizontal runs
Long horizontal drains need cleanouts at set intervals so any part can be reached – commonly around every 100 ft.
Building drain / sewer cleanout
A cleanout is required near where the building drain leaves the structure to rod toward the sewer or septic.
Cleanout accessibility
Every cleanout must stay accessible – never tiled, drywalled, buried, or landscaped over.
Cleanout size
Cleanouts are generally full pipe size up to a limit (commonly 4 in), then a minimum size for larger pipe.
Cleanout clearance for rodding
Cleanouts need clear space in front to insert a rod or cable – a cleanout jammed against a wall is useless.
Exterior / yard cleanouts
Underground and yard cleanouts are brought to grade in an accessible box so the line can be serviced from outside.
Cleanout direction of flow
Cleanouts must open in a way that lets a rod travel with the flow of the drain, not fight it.
Cleanout equivalents at fixtures
A removable fixture trap or a floor-drain body can serve as a cleanout where the code specifically allows it.
Air gap – the strongest protection
An air gap is a physical vertical space between a potable outlet and the flood rim of a receptor; it cannot be bypassed and is the best backflow protection.
Atmospheric vacuum breaker (AVB)
An AVB protects against back-siphonage only, must sit above the flood rim, and cannot have downstream shutoffs or continuous pressure.
Pressure vacuum breaker (PVB)
A PVB protects against back-siphonage under continuous pressure and is common on irrigation; it mounts above the highest downstream outlet.
Reduced-pressure principle (RPZ)
An RPZ assembly protects against both back-siphonage and back-pressure and is used on high-hazard connections; it discharges from a relief port and needs a drain.
Double-check valve assembly
A double-check assembly protects low-hazard connections against back-pressure and back-siphonage but is not for high-hazard use.
Hose bibb vacuum breaker
Threaded hose connections need a hose-bibb vacuum breaker so a hose in a bucket or pool cannot siphon back.
Irrigation system backflow
Lawn irrigation is a backflow hazard (chemicals, standing water) and needs the assembly matching the hazard, often a PVB or RPZ.
Boiler and closed-loop protection
Boilers, chemically treated systems, and closed loops connecting to potable water need high-hazard protection, generally an RPZ.
Fill valves and ballcocks
Toilet fill valves and similar must be listed anti-siphon types set above the overflow so tank water cannot siphon back.
Backflow assembly testing
Testable backflow assemblies (RPZ, DCVA, PVB) generally must be tested at install and periodically by a certified tester.
No unprotected cross-connections
Direct connections between potable water and any non-potable source, waste, or chemical are prohibited without approved protection.
Chemical dispensers and aspirators
Chemical dispensers, aspirators, and dental/lab equipment that mix into the water stream need backflow protection matched to the hazard.
Fire sprinkler connection
Connections to fire-protection systems can require backflow protection based on the system type and any antifreeze or additives.
Non-potable clearly identified
Non-potable, reclaimed, or graywater piping must be marked and separated so no one confuses it with potable water.
Approved materials by application
Each material is listed for specific uses – water distribution, DWV, or underground – and must be used only where listed.
Copper tube and joints
Copper is joined by soldering, brazing, or listed press or mechanical fittings; use the right temper and wall type for the service.
PEX tubing and fittings
PEX uses listed cold-expansion, crimp, clamp, or push fittings; keep it from UV, high heat, and incompatible chemicals.
CPVC for hot and cold water
CPVC handles hot pressurized water with proper solvent cement and cure time, and needs allowance for expansion.
PVC DWV solvent-weld joints
PVC drain pipe is solvent-welded with primer and cement rated for the pipe; joints must be clean, fully seated, and cured.
ABS DWV joints
ABS drain pipe uses its own one-step cement; do not mix ABS and PVC cements or transition without a listed method.
Cast iron – hub and no-hub
Cast iron DWV joins by hub-and-spigot with gaskets or by no-hub couplings with the correct torque and support.
Dielectric separation of dissimilar metals
Where dissimilar metals connect (copper to steel), use a dielectric union or listed connector to slow galvanic corrosion.
Transition fittings between materials
Changing pipe materials requires listed transition fittings made for that pair, not improvised adapters.
Hanger and support spacing
Support spacing is set by material and size so pipe does not sag; plastic needs closer support than metal, and vertical pipe needs support at each floor.
Expansion and contraction
Long runs, especially plastic and hot lines, need offsets or loops so thermal movement does not stress joints.
Underground piping material
Buried water and DWV piping must be a material listed for direct burial and bedded so it is not crushed or point-loaded.
No lead in potable systems
Wetted components in potable water must meet the low-lead requirement – solder, fittings, and fixtures.
Prohibited and reused materials
Used pipe and fittings, and materials not listed for the service, are generally not allowed in new work.
Fittings must suit flow
Drainage fittings must be drainage-pattern; pressure fittings and vent-pattern fittings cannot substitute on flowing drains.
Gaskets and mechanical joints
Gasketed and mechanical joints must be listed, properly lubricated, and fully seated per the maker to seal reliably.
Fixture-unit sizing method
Supply and drain sizing both run on fixture units – total the load, then use the code table or curve to pick pipe size.
Water demand from WSFU
Total WSFU is converted to a peak gpm demand (Hunter curve) that, with pressure and length, sets the pipe size.
Pressure available vs required
Sizing balances the pressure available at the meter against losses in pipe, fittings, height, meter, and backflow device, leaving each fixture its minimum.
Pressure-reducing valve (PRV)
When static pressure is too high (over about 80 psi), a PRV protects fixtures and appliances and creates a closed system needing expansion control.
Booster and low-pressure fixes
Where street pressure is too low for the building height, an approved booster or pump system is used, sized to demand.
Head loss from elevation
Every foot of height above the source costs pressure (about 0.43 psi per foot), which sizing must account for.
Velocity and water hammer
Oversized flow velocity causes noise, erosion, and water hammer; sizing keeps velocity in the accepted range.
Drainage sizing recap
Drains are sized by total DFU and slope, with the stack never smaller than its largest branch and no reduction downstream.
Vent sizing recap
Vents are sized from the drain served and the developed vent length, so pressures stay balanced.
Simultaneous vs total demand
Sizing uses probable simultaneous demand, not the sum of every fixture running at once, which is why fixture-unit curves flatten out.
Meter and service sizing
The meter and service must be sized for peak demand; an undersized meter throttles the whole building.
Thermal expansion sizing
The expansion device on a closed system is sized to the water heater volume and the pressure conditions.
Storm and sanitary kept separate
Storm drainage (roof, area, and foundation water) generally must not connect to the sanitary system unless a combined sewer is specifically approved.
Sizing roof drains and leaders
Roof drains, leaders, and horizontal storm drains are sized from the roof area served and the local rainfall rate.
Secondary (overflow) roof drainage
Roofs that could pond need secondary or overflow drainage so a blocked primary drain cannot overload the structure.
Area drains and yard drains
Paved areas, courts, and window wells use area drains sized for their catchment and connected to an approved storm point.
Subsoil / foundation drains to sump
Foundation and subsoil drains typically discharge to a sump that pumps to an approved storm location, never the sanitary sewer.
Sump and sewage ejector pits
Sanitary fixtures below gravity level drain to a sealed, vented sump with an ejector pump sized for the load and solids.
Ejector solids handling and check valve
Sewage ejectors must pass the required solids size and have a check valve and shutoff so effluent cannot flow back into the pit.
Sump venting
Sanitary sumps and ejector pits must be vented so the pump can move sewage and gases do not build up.
Backwater valve for below-grade fixtures
Fixtures below the upstream manhole rim need a backwater valve so a surcharged main does not flood them, and it must stay accessible.
No storm into sanitary (and vice versa)
Cross-connecting storm and sanitary overloads treatment and causes backups; keep the systems independent unless a combined system is approved.
Approved storm materials and slope
Storm piping uses listed materials and is sloped to drain by gravity like sanitary, sized for the design storm.
Sump pump discharge
Sump and storm pump discharge must reach an approved point (storm sewer, drywell, or daylight) without creating a hazard or nuisance.
Gas piping is its own code
Fuel-gas piping is governed by the fuel-gas / mechanical code (and utility rules), not the plumbing drainage or water chapters – treat it as a separate discipline.
Gas pipe sizing
Gas piping is sized from the connected appliance BTU load, the pipe length, and the gas type and pressure using the fuel-gas sizing tables.
Sediment trap (drip leg)
Most gas appliances need a sediment trap ahead of the appliance connection to catch debris and moisture before it reaches the control.
Appliance shutoff valve
Each gas appliance needs an accessible manual shutoff valve in the same room, within reach of the appliance.
CSST bonding
Corrugated stainless steel tubing (CSST) generally must be bonded to the electrical grounding system to reduce lightning-related damage per the maker and code.
Gas pressure test
New gas piping must be pressure-tested and hold for the required time before the utility or AHJ approves it.
Approved gas materials and joints
Gas uses listed pipe (black steel, CSST, listed PE underground) with joints and thread compound rated for gas.
Appliance connectors and clearances
Listed flexible appliance connectors and required clearances to combustibles apply; connectors cannot run through walls or floors.
Water closet side clearance
A water closet needs a minimum clearance from its centerline to any wall or adjacent fixture so it is usable.
Water closet front clearance
A minimum clear space is required in front of a water closet and other fixtures.
Lavatory clearances and spacing
Lavatories need clearance in front and, when set side by side, minimum center-to-center spacing.
Shower compartment size
Shower stalls need a minimum floor area and a minimum interior dimension so they are usable.
Fixture rough-in dimensions
Each fixture has standard rough-in dimensions (drain height, supply height, closet flange offset) that must match the fixture chosen.
Closet flange height
The closet flange is set on top of the finished floor at the right height so the wax seal seats properly.
Accessible clear floor space
Accessible fixtures need defined clear floor space and approach that goes beyond the standard plumbing minimums.
Wall backing and fixture support
Wall-hung fixtures and grab bars need solid backing or carriers so they do not pull loose.
Urinal and partition spacing
Urinals set side by side and near partitions need minimum spacing for use and cleaning.
Fixture sealing to wall/floor
Fixtures must be sealed to adjacent surfaces (caulk or approved sealant) so water does not get behind or under them.
Medical gas and vacuum – specialist only
Medical gas and vacuum systems are a highly regulated specialty with certified installers, brazing, and verification – well beyond general plumbing.
Graywater / reclaimed water systems
Graywater and reclaimed-water systems have their own rules for separation, marking, filtration, and use, and require AHJ approval.
Rainwater harvesting
Rainwater catchment for non-potable (or treated potable) use has specific storage, screening, overflow, and cross-connection rules.
Solar thermal water heating
Solar hot-water systems add rules for heat-transfer fluids, expansion, overtemperature protection, and freeze protection.
Special/laboratory and acid waste
Lab and acid-waste systems need chemical-resistant piping, neutralization, and separation from the sanitary system.
Nonpotable identification and separation
All nonpotable systems must be clearly marked, color-coded, and physically separated so they can never cross-connect with potable water.
DWV rough-in test
The drain, waste, and vent system is tested at rough-in (water or air) and must hold the required pressure without loss.
Water (head) test on DWV
A common DWV test fills the system with water to a set head (often 10 ft) and holds it for the required time.
Water supply pressure test
The water distribution system is pressure-tested (water or air) to the required pressure and must hold before it is covered.
Final test
At completion, a final air or smoke test and inspection confirm the system is tight and traps hold their seals.
Required inspections
Typical inspections include underground, rough-in, and final; work cannot be covered until the AHJ approves each stage.
Building sewer test
The building sewer is tested (air or water) for tightness before backfill.
Disinfection before use
New potable piping is flushed and disinfected and, where required, sampled before it is placed in service.
Backflow assembly acceptance test
Testable backflow assemblies are tested by a certified tester at installation and on the AHJ schedule.
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