BTEB Plumbing cheat sheet

Fixture unit (FU): one water closet equals about 3 FU on the drainage side and 2.5 FU on the supply side; convert fixture counts to FU before sizing any pipe.

Building drain runs horizontally from the building to the building sewer; building sewer begins outside the foundation wall and slopes at least 1/4 in per ft (2%) for small pipe.

Vent stack must extend at least 6 in above the roof surface and at least 12 in above any roof area within 10 ft of it when used for other purposes.

Trap arm length limit depends on pipe size: about 5 ft for 1.5 in, 6 ft for 2 in, 8 ft for 3 in, and 10 ft for 4 in trap arms, measured from trap weir to vent.

Water service sizing uses the peak demand in gpm from total supply FU, then selects pipe from a pressure-loss table accounting for developed length plus equivalent length of fittings.

Static pressure at a fixture = supply pressure minus 0.433 psi per ft of elevation rise above the source; 1 ft of water column equals 0.433 psi.

Each water closet needs a 3 in drain minimum; a lavatory needs 1.25 in, a bathtub 1.5 in, and a kitchen sink 1.5 in drain.

Slope rules: 2.5 in and smaller drain pipe at 1/4 in per ft; 3 in and larger may use 1/8 in per ft where the run permits, but never less than 1/8 in per ft.

Copper types: K is thickest (underground and heavy duty), L is standard for interior water lines, M is thin-wall for above-ground low-pressure use, DWV is for drainage only.

PEX is rated by temperature/pressure: PEX-A and PEX-B are common for potable water; use brass or copper fittings with PEX for potable lines and follow manufacturer ratings.

PVC schedule 40 is for DWV and cold water; CPVC is rated for hot water up to about 200 F at reduced pressure; do not interchange solvent cements between PVC and CPVC.

Solvent cement joint: cut square, deburr, clean with primer, apply cement to both surfaces, insert with a quarter turn, hold 30 seconds, and let cure fully before pressure testing.

Galvanized steel pipe is joined by threaded fittings; never join galvanized to copper directly without a dielectric union to prevent galvanic corrosion.

Cast iron soil pipe joins by hub-and-spigot with oakum and lead or by no-hub couplings with stainless steel bands and neoprene gaskets.

Copper soldering: use lead-free solder, flux for the metal type, heat the fitting not the solder, and keep the joint dry; brazing is used for medical gas and high temperatures.

Pipe support spacing increases with pipe size; plastic pipe needs closer supports than metal because it sags more at elevated temperature.

Water closet flush volumes: standard is 1.6 gallons per flush; high-efficiency models use 1.28 gpf or less; urinals commonly use 1.0 gpf or less.

A trap seal must be at least 2 in and no more than 4 in deep; every fixture except a direct-connected appliance needs a trap.

A 2 in trap and trap arm can serve a lavatory or bathtub; a water closet needs a 3 in drain and a 2 in vent.

Drainage fixture units by fixture: water closet 3, lavatory 1, bathtub 2, shower 2, kitchen sink 2, floor drain 2, washing machine 2, dishwasher 2.

A vent must rise vertically at least 6 in above the fixture's flood-level rim before it can turn horizontal, and horizontal vents must slope back to the drain.

A wet vent may serve one or two fixtures on a single floor when the vent pipe is one size larger than the drain it serves.

A cleanout is required at the base of each stack, at each horizontal run change greater than 45 degrees, and at the building sewer, spaced no more than 100 ft apart on horizontal drains.

Backwater valves are required where the building drain is below the level of the next upstream manhole, to prevent sewage backup into the building.

Backflow prevention: an air gap is the highest protection; a reduced-pressure zone (RPZ) device is used for high hazard; a double check valve for low hazard; never rely on a simple check valve for health hazard protection.

Water heater relief valve must be set at or below the tank's rated pressure, piped full size to within 6 in of the floor or to a drain, and never capped or plugged.

Trench safety: any trench 5 ft deep or more requires a protective system (shoring, sloping, or shielding) unless in stable rock; a competent person must inspect daily.

Sloping in Type C soil is 1.5 to 1 (horizontal to vertical); Type B is 1 to 1; Type A is 3/4 to 1; never enter an unprotected trench deeper than 5 ft.

Soldering safety: purge flammable gas lines, use a fire watch near combustibles, and keep a fire extinguisher within reach; lead-free solder is required on potable water lines.

Estimating takeoff: count fixtures and fittings from drawings, add waste factor of about 5-10 percent for pipe, and price labor by fixture or by linear feet of pipe plus fittings.

Labor units for estimating are commonly expressed in hours per fixture or per 100 ft of pipe; add overhead and profit as a percentage on top of material plus labor.

Pressure testing: water piping is tested at 1.5 times working pressure but not less than 100 psi for at least 2 hours; DWV systems are tested with water or air to 10 ft of head or 5 psi.

Confined space entry requires testing for oxygen, flammables, and toxic gas before entry, with an attendant and rescue plan in place.

Copper type K is thickest, L is standard interior, M is thin-wall, DWV is drainage only; match type to service pressure and location.

PEX is flexible cross-linked polyethylene; use brass or copper fittings for potable water and follow manufacturer temperature and pressure ratings.

PVC schedule 40 is for DWV and cold water; CPVC is rated for hot water up to about 200 F at reduced pressure; never interchange solvent cements.

Solvent cement joint: cut square, deburr, prime, apply cement to both surfaces, insert with a quarter turn, hold 30 seconds, and cure fully before testing.

Galvanized steel is joined by threaded fittings; use a dielectric union between galvanized and copper to prevent galvanic corrosion.

Cast iron soil pipe joins by hub-and-spigot with oakum and lead or by no-hub couplings with stainless bands and neoprene gaskets.

Copper soldering uses lead-free solder and flux matched to the metal; heat the fitting, not the solder, and keep the joint dry.

Plastic pipe needs closer support spacing than metal pipe because it sags more at elevated temperature.

Water closet flush volumes: standard 1.6 gpf; high-efficiency 1.28 gpf or less; urinals commonly 1.0 gpf or less.

Trap seal must be 2 to 4 in deep; every fixture except direct-connected appliances needs a trap.

Drainage fixture units: water closet 3, lavatory 1, bathtub 2, shower 2, kitchen sink 2, floor drain 2, washing machine 2, dishwasher 2.

A vent must rise at least 6 in above the flood-level rim before turning horizontal, and horizontal vents slope back to the drain.

A wet vent may serve one or two fixtures on a single floor when the vent pipe is one size larger than the drain it serves.

Cleanouts are required at the base of each stack, at horizontal changes over 45 degrees, and at the building sewer, spaced no more than 100 ft apart.

A backwater valve is required where the building drain is below the next upstream manhole, to prevent sewage backup.

A 2 in trap and trap arm can serve a lavatory or bathtub; a water closet needs a 3 in drain and a 2 in vent.

Backflow protection: air gap is highest; an RPZ device is for high hazard; a double check valve is for low hazard; never rely on a simple check valve for health hazards.

Water heater relief valve must be set at or below the tank rating, piped full size to within 6 in of the floor or to a drain, and never capped.

Trench safety: any trench 5 ft deep or more needs a protective system unless in stable rock; a competent person inspects daily.

Soil sloping: Type C is 1.5 to 1, Type B is 1 to 1, Type A is 3/4 to 1; never enter an unprotected trench deeper than 5 ft.

Soldering safety: purge flammable gas lines, use a fire watch near combustibles, and keep a fire extinguisher within reach; lead-free solder is required on potable lines.

Estimating takeoff: count fixtures and fittings, add 5-10 percent waste on pipe, and price labor by fixture or linear feet of pipe plus fittings.

Labor units are expressed in hours per fixture or per 100 ft of pipe; add overhead and profit as a percentage of material plus labor.

Pressure testing: water piping at 1.5 times working pressure but not less than 100 psi for at least 2 hours; DWV tested with water or air to 10 ft of head or 5 psi.

Fixture unit (FU): one water closet equals about 3 FU on the drainage side and 2.5 FU on the supply side; convert fixture counts to FU before sizing.

Building drain runs horizontally from the building to the building sewer; building sewer begins outside the foundation wall and slopes at least 1/4 in per ft (2%) for small pipe.

Vent stack must extend at least 6 in above the roof and at least 12 in above any roof area within 10 ft when used for other purposes.

Trap arm length limit depends on pipe size: about 5 ft for 1.5 in, 6 ft for 2 in, 8 ft for 3 in, and 10 ft for 4 in, measured from trap weir to vent.

Water service sizing uses peak demand in gpm from total supply FU, then selects pipe from a pressure-loss table that accounts for developed length plus equivalent length of fittings.

Static pressure at a fixture equals supply pressure minus 0.433 psi per ft of elevation rise; 1 ft of water column equals 0.433 psi.

Each water closet needs a 3 in drain minimum; a lavatory needs 1.25 in, a bathtub 1.5 in, and a kitchen sink 1.5 in drain.

Slope rules: 2.5 in and smaller drain pipe at 1/4 in per ft; 3 in and larger may use 1/8 in per ft where the run permits, but never less than 1/8 in per ft.

Copper type K is thickest, L is standard interior, M is thin-wall, DWV is drainage only; match type to service pressure and location.

PEX is flexible cross-linked polyethylene; use brass or copper fittings for potable water and follow manufacturer temperature and pressure ratings.

PVC schedule 40 is for DWV and cold water; CPVC is rated for hot water up to about 200 F at reduced pressure; never interchange solvent cements.

Solvent cement joint: cut square, deburr, prime, apply cement to both surfaces, insert with a quarter turn, hold 30 seconds, and cure fully before testing.

Galvanized steel is joined by threaded fittings; use a dielectric union between galvanized and copper to prevent galvanic corrosion.

Cast iron soil pipe joins by hub-and-spigot with oakum and lead or by no-hub couplings with stainless bands and neoprene gaskets.

Copper soldering uses lead-free solder and flux matched to the metal; heat the fitting, not the solder, and keep the joint dry.

Plastic pipe needs closer support spacing than metal pipe because it sags more at elevated temperature.

Water closet flush volumes: standard 1.6 gpf; high-efficiency 1.28 gpf or less; urinals commonly 1.0 gpf or less.

Trap seal must be 2 to 4 in deep; every fixture except direct-connected appliances needs a trap.

Drainage fixture units: water closet 3, lavatory 1, bathtub 2, shower 2, kitchen sink 2, floor drain 2, washing machine 2, dishwasher 2.

A vent must rise at least 6 in above the flood-level rim before turning horizontal, and horizontal vents slope back to the drain.

A wet vent may serve one or two fixtures on a single floor when the vent pipe is one size larger than the drain it serves.

Cleanouts are required at the base of each stack, at horizontal changes over 45 degrees, and at the building sewer, spaced no more than 100 ft apart.

A backwater valve is required where the building drain is below the next upstream manhole, to prevent sewage backup.

A 2 in trap and trap arm can serve a lavatory or bathtub; a water closet needs a 3 in drain and a 2 in vent.

Backflow protection: air gap is highest; an RPZ device is for high hazard; a double check valve is for low hazard; never rely on a simple check valve for health hazards.

Water heater relief valve must be set at or below the tank rating, piped full size to within 6 in of the floor or to a drain, and never capped.

Trench safety: any trench 5 ft deep or more needs a protective system unless in stable rock; a competent person inspects daily.

Soil sloping: Type C is 1.5 to 1, Type B is 1 to 1, Type A is 3/4 to 1; never enter an unprotected trench deeper than 5 ft.

Soldering safety: purge flammable gas lines, use a fire watch near combustibles, and keep a fire extinguisher within reach; lead-free solder is required on potable lines.

Estimating takeoff: count fixtures and fittings, add 5-10 percent waste on pipe, and price labor by fixture or linear feet of pipe plus fittings.

Labor units are expressed in hours per fixture or per 100 ft of pipe; add overhead and profit as a percentage of material plus labor.

Pressure testing: water piping at 1.5 times working pressure but not less than 100 psi for at least 2 hours; DWV tested with water or air to 10 ft of head or 5 psi.