IA Plumber cheat sheet

A plumbing permit and inspections are required before work begins; piping must be tested and approved before concealment.

Materials must be approved and listed; used or defective materials may be installed only with approval of the authority having jurisdiction.

Drainage and vent systems are tested with a 10-foot water head or 5 psi of air for at least 15 minutes.

Water supply systems are hydrostatically tested at 100 psi, or at working pressure when that is higher, for 60 minutes.

Piping passing through foundation walls must be sleeved and sealed with a flexible, corrosion-resistant material.

Pipe must be protected from freezing, corrosion, and physical damage; water service is buried below the local frost line.

Pipe in trenches requires proper bedding and continuous support; support spacing follows the table for each pipe material.

Joints requiring maintenance must remain accessible; concealed mechanical joints and unions are limited to approved locations.

The authority having jurisdiction (AHJ) enforces the code; 'approved' means accepted by the AHJ, usually through listing by a testing agency.

The building drain receives waste inside the building and extends 30 inches beyond the outside face of the wall; the building sewer continues from there.

A soil stack carries sewage, a waste stack carries non-fecal waste, and a vent stack serves the drainage system.

A drainage fixture unit (dfu) expresses the probable waste flow a fixture contributes to the drainage system.

Developed length is the pipe length measured along the centerline, including the allowance for fittings.

Trap seal is the vertical water depth in a trap, measured from the trap weir to the top of the dip.

Flood level rim is the edge of a receptacle from which water overflows when it is filled to capacity.

A cross-connection is any actual or potential connection between potable water and a nonpotable source.

1 psi equals 2.31 feet of water column; 1 foot of water column equals 0.433 psi, so pressure = 0.433 × height in feet.

Flow equation Q = A × V; 1 gallon per minute equals 0.002228 cubic feet per second, and 1 cfs equals 448.8 gpm.

Circle area = π d²/4 = 0.7854 d²; volume in gallons = cubic feet × 7.48.

Hazen-Williams head loss: h = 4.727 L Q^1.852 / (C^1.852 d^4.87), with h and d in feet, Q in cfs, and L in feet.

Offset multipliers: 45° travel = 1.414 × offset; 22.5° = 2.613; 60° = 1.155.

Slope conversions: 1/4 inch per foot = 2 percent; 1/8 inch per foot = 1 percent; fall = slope × length.

Drainage fixture units commonly used: water closet 3, lavatory 1, bathtub 2, shower 2, kitchen sink 2, washing machine 2.

Water supply fixture units commonly used: tank water closet 2.5, flushometer water closet 10, lavatory 1, bathtub 2, shower 2.

Pipe expansion: ΔL = L × α × ΔT; for steel, α is about 6.5 × 10⁻⁶ inch per inch per degree Fahrenheit.

Drainage pipe 2 inches and smaller slopes at 1/4 inch per foot; 3-inch and larger pipe may slope at 1/8 inch per foot where approved.

Cleanouts are required at the base of each stack, at changes of direction of 45 degrees or more, at intervals not exceeding 100 feet, and at the building sewer.

A horizontal drain turning to vertical must use long-radius fittings or an approved combination of 45-degree bends.

Sanitary tees are not permitted on horizontal drainage lines or on their backs; wyes and combination fittings are used instead.

The fall of a trap arm may not exceed one pipe diameter, and the trap arm must be vented within its permitted length.

The building sewer is sized from total drainage fixture units and slope, with a 3-inch minimum size typical.

A backwater valve is required where fixtures are below the elevation of the next upstream manhole or the street.

Vertical stacks must be supported at the base and restrained against lateral movement at each floor level.

Every trap requires a vent except where a combination waste and vent system is specifically approved.

Vent pipe must be at least 1-1/4 inch in size and may not be smaller than required for the fixture units served.

A fixture vent must rise at least 6 inches above the flood level rim before any horizontal offset.

Vent terminals extend at least 6 inches above the roof, or 12 inches where snow is likely, and must be unobstructed.

Vent piping is graded so that moisture drains back to the drainage system, typically at 1/4 inch per foot.

A wet vent also serves as a drain and is generally limited to a bathroom group on the same floor.

A common vent may serve two fixture traps on the same floor when it is sized for the combined fixture units.

An island sink uses a loop vent installed below the floor with an accessible cleanout.

Air admittance valves are permitted only where approved, must be accessible, and require an air intake opening.

A trap must maintain a water seal of at least 2 inches and not more than 4 inches.

Each fixture is separately trapped, except where a single trap is specifically permitted for a set of fixtures.

S-traps, double traps, and bell traps are prohibited; drum traps are allowed only for special wastes where approved.

A grease interceptor is required for commercial kitchens and is sized by fixture load and flow.

Sand and oil interceptors are required for garages, repair shops, and similar facilities.

Interceptors must be accessible for cleaning and have removable, gastight covers.

A floor drain trap subject to evaporation requires a trap primer to maintain the seal.

Fats, oils, grease, sand, oil, and harmful chemicals may not be discharged to the drainage system without treatment.

Fixtures must receive at least 8 psi residual pressure under normal flow; flushometer valves typically require 15 to 25 psi.

A pressure-reducing valve is required when supply pressure exceeds 80 psi and is commonly set to 50 psi.

Design velocity is typically kept at 4 to 8 feet per second; higher velocities cause noise and erosion.

Water service pipe is buried below the frost line and protected from freezing and corrosion.

Water hammer arrestors are installed near quick-closing valves to absorb shock waves.

A closed system with a backflow preventer requires a thermal expansion tank.

Copper horizontal pipe is typically supported every 6 feet and vertical pipe every 10 feet, subject to the material table.

A corporation stop is installed at the main, a curb stop at the property line, and the meter downstream of the curb stop.

Federal maximums: water closet 1.6 gpf, urinal 1.0 gpf, showerhead 2.5 gpm at 80 psi, lavatory faucet 2.2 gpm at 60 psi.

A water closet must be at least 15 inches from its centerline to any side wall and have at least 21 inches of clearance in front.

Fixture tailpieces may not exceed 24 inches from the fixture outlet to the trap.

A fixture drain air gap must be at least 1 inch or twice the drain diameter, whichever is greater.

Floor drains require a trap seal and a primer where evaporation can occur.

Escutcheons are required where fixture supply or waste piping penetrates a wall or floor.

Accessible lavatories require knee clearance and insulated drain and supply piping.

Fixture fittings must be of approved type, and slip joints must be accessible.

A temperature and pressure relief valve is typically set to open at 210 degrees Fahrenheit or 150 psi, whichever occurs first.

The TPR valve must not be capped, and its discharge pipe must be full size, flow by gravity, and have an unthreaded end.

The relief discharge terminates 6 inches above the floor or outside the building where it cannot cause injury.

A drain pan is required where a leak would cause damage, with the pan drain routed to a safe location.

A water heater in a garage must be elevated so its ignition source is at least 18 inches above the floor.

A thermal expansion tank is required on closed systems where a backflow preventer or check valve is installed.

Seismic strapping uses two straps, one in the upper third and one in the lower third of the tank.

Delivered water temperature is typically limited to 120 degrees Fahrenheit, with higher storage temperatures using a mixing valve.

Gas piping is sized by the longest-length method using gas specific gravity, available pressure, and allowable pressure drop.

A sediment trap or drip leg is installed downstream of the appliance shutoff valve and upstream of the controls.

A manual shutoff valve must be installed within 6 feet of the appliance and be readily accessible.

Appliance connectors may not exceed 6 feet and may not pass through walls, floors, or ceilings.

Low-pressure gas piping is commonly tested with air at 10 psi for 10 minutes with no pressure drop.

Gas piping must be bonded to the grounding electrode system; CSST is installed per the manufacturer's instructions.

Unions and mechanical joints are permitted only in accessible locations.

Appliances require venting and clearance to combustibles per their listing and the manufacturer's instructions.

A regulator vent must terminate outdoors in a location protected from water and debris.

An air gap is the only absolute method of backflow prevention and is required for high-hazard connections.

A reduced-pressure principle assembly is used for high hazards; a double check valve assembly is used for low hazards.

A pressure vacuum breaker is commonly used for irrigation systems and must be installed above the highest downstream outlet.

Backflow assemblies must be tested at installation and annually by a certified tester.

Backsiphonage is caused by negative pressure in the supply; backpressure is caused by downstream pressure exceeding supply pressure.

Cross-connections between potable water and nonpotable sources are prohibited.

Hose bibbs require vacuum breakers to prevent contamination from hoses and attachments.

An atmospheric vacuum breaker may not be under continuous pressure for more than 12 hours.