FL Plumber cheat sheet

Break-even volume in units = fixed costs ÷ (unit selling price − unit variable cost).

Gross margin % = (revenue − cost of goods sold) ÷ revenue × 100; net profit = gross profit − overhead, interest and taxes.

Markup is calculated on cost while margin is calculated on selling price, so a 25% markup equals a 20% gross margin.

Working capital = current assets − current liabilities; current ratio = current assets ÷ current liabilities, and a ratio below 1.0 signals an inability to cover short-term obligations.

Straight-line depreciation = (asset cost − salvage value) ÷ useful life in years.

Overhead items such as insurance, office rent, and truck payments are indirect costs and must be recovered through markup, not charged to a single job.

A contractor improving real property in Florida generally pays state sales tax (6%) on materials at the point of purchase rather than collecting tax from the customer on the contract.

Job cost = labor + material + equipment + subcontractor + permits; compare it to the estimate at least monthly to catch overruns before the job closes.

A change order must be in writing and signed by the owner and the contractor; it modifies the contract sum, the contract time, or both.

In Florida, a subcontractor or material supplier preserves lien rights by serving a Notice to Owner on the owner and lender no later than 45 days after first furnishing labor or materials.

A Notice of Commencement must be recorded and posted before work begins on an improvement costing more than the statutory threshold, and it must name the surety and lender.

A construction lien claim in Florida must be recorded within 90 days after final furnishing of labor, services, or materials.

The critical path is the longest sequence of dependent activities; it determines project duration and carries zero total float.

Retainage on private Florida work is commonly 10% of each progress payment; on public work it is reduced to 5% after 50% completion.

Common contract types are lump sum (fixed price), unit price (paid per measured quantity), cost-plus (cost plus a fee), and time and material.

Substantial completion means the work is usable for its intended purpose; it starts warranty periods and triggers many statutory lien and payment deadlines.

The Florida Plumbing Code is adopted from the International Plumbing Code; "shall" indicates a mandatory requirement and "should" indicates an advisory recommendation.

A fixture trap must have a water seal of at least 2 inches and not more than 4 inches in depth.

Every trap must be vented, and S-traps and the double-trapping of a single fixture are prohibited.

The minimum vent pipe size is 1-1/4 inch, and a vent terminating through a roof must extend at least 6 inches above the roof surface (7 feet where the roof is used for other than weather protection).

A water closet requires at least 15 inches from its centerline to any side wall, a clear width of 30 inches, and 21 inches of clearance in front of the bowl.

A lavatory must be set at least 4 inches from an adjacent side wall.

Potable water connections to nonpotable systems require an approved air gap or backflow preventer, and testable backflow assemblies must be tested at installation and annually thereafter.

A permit and the required inspections must be obtained before work begins, and concealed piping cannot be covered until it has been inspected and approved.

Typical fixture unit values for water supply sizing: tank-type water closet 2.5, flushometer water closet 6, lavatory 1, kitchen sink 1.5, bathtub 4, shower 2.

Static pressure changes 0.434 psi per foot of elevation, so a 10-foot rise reduces pressure by about 4.34 psi.

Minimum residual pressure is generally 8 psi at fixtures and 15 psi at flushometer valves; below that, fixtures will not function properly.

Design water velocity in service and distribution piping in the range of about 5 to 8 feet per second to limit noise, erosion, and pressure loss.

A check valve or backflow preventer creates a closed system, so a thermal expansion tank is required at the water heater.

Dielectric unions must separate copper piping from steel or galvanized piping to prevent galvanic corrosion.

Water hammer arrestors are installed near quick-closing valves such as flushometers and solenoid-operated appliances to absorb shock.

Sizing procedure: total the fixture units, convert to probable demand in gpm from the code curve, then select pipe size that limits velocity and friction loss within the available pressure.

Minimum slope is 1/4 inch per foot for pipe 2-1/2 inches and smaller and 1/8 inch per foot for pipe 3 inches and larger.

Typical drainage fixture unit values: water closet 4, lavatory 1, bathtub 2, shower 2, kitchen sink 2.

The building drain is the lowest piping inside the building; the building sewer is the pipe carrying the building drain discharge to the public sewer or private disposal system.

Cleanouts are required at the base of each stack, at the end of the building drain, and at changes of direction greater than 45 degrees.

A backwater valve is required on fixtures whose flood-level rim is below the next upstream manhole cover.

A vent stack carries air only, while a stack vent is the extension of a soil or waste stack above the highest fixture connection.

Trap arm length is limited by pipe size to prevent self-siphoning: 1-1/4 inch = 5 feet, 1-1/2 inch = 6 feet, 2 inch = 8 feet.

Each trap must be vented within the allowable trap-arm distance, or the trap seal will be siphoned out.

A water heater requires a temperature and pressure relief valve set to open at 210 degrees Fahrenheit or 150 psi, installed within the top 6 inches of the tank.

The relief valve discharge pipe must be full size, unthreaded at the outlet, not trapped, and terminate not more than 6 inches above the floor.

Food-service sinks and dishwashers require an air gap of at least 1 inch or twice the pipe diameter, whichever is larger, or an approved air-gap fitting.

Grease interceptors are required for food establishments; they retain fats, oils, and grease and must be sized to fixture flow and cleaned on a regular schedule.

A clothes washer standpipe must be at least 18 inches and not more than 42 inches above the trap weir, with a 2-inch trap.

Floor drains that receive no regular flow need a trap primer to replace evaporative loss and keep the trap seal intact.

Emergency eyewash and shower units must supply tepid water and be located within about 10 seconds' travel of the hazard.

An automatic dishwasher must discharge through an air gap or an approved high-loop arrangement before connecting to the drainage system.

A protective system (sloping, benching, shoring, or a trench shield) is required once an excavation reaches 5 feet, and at any depth when a competent person identifies a hazard.

Spoil piles and heavy equipment must be kept at least 2 feet back from the edge of an excavation.

A ladder must be placed in a trench so that no worker travels more than 25 feet laterally, and it must extend 3 feet above the surface.

Fall protection is required in construction whenever workers are exposed to a fall of 6 feet or more to a lower level.

Before confined-space entry the atmosphere must be tested; acceptable oxygen is 19.5 to 23.5 percent, and permit spaces require an attendant and continuous monitoring.

All 120-volt, single-phase, 15- and 20-ampere receptacles on construction sites must have GFCI protection.

Ladders are set at a 4:1 angle - 1 foot out from the wall for every 4 feet of height - and secured against displacement.

A fire watch must remain in place for at least 30 minutes after soldering, brazing, or other hot work is completed.

Soldering and cutting require eye protection, gloves, and ventilation to control flux and lead fume exposure.

A scale of 1/4 inch = 1 foot means each quarter inch on the drawing equals one foot; multiply the scaled measurement by 48 to convert to inches.

One cubic foot holds 7.48 gallons, and one gallon of water weighs 8.34 pounds.

One psi equals 2.31 feet of water column, and one foot of head equals 0.433 psi.

A 1/4 inch per foot slope equals approximately 2.08% grade; a 1/8 inch per foot slope equals approximately 1.04%.

Pipe takeoff: measure the longest developed run, add fitting allowances and vertical drops, then add 5 to 10% for waste and cuts.

Copper tube wall thickness from heaviest to lightest is Type K, Type L, Type M; Type L is the common choice for interior water distribution.

PVC Schedule 80 has a thicker wall than Schedule 40 but uses the same solvent-cement joining method; ABS is joined with ABS cement.

A plan view shows the horizontal layout, a riser diagram shows vertical relationships and pipe sizes, and an isometric shows the system in three dimensions.