MS Plumber cheat sheet

Permits are required before installing, altering, or replacing plumbing systems; ordinary repairs such as replacing a faucet washer or clearing a stoppage do not require a permit.

Inspections follow a fixed sequence: rough-in (before concealment), then final; concealed work must be inspected and approved before being covered, or the plumber may be required to expose it.

Code adoption hierarchy: model code (e.g., Uniform Plumbing Code) as amended by state statute, then local ordinance; the most restrictive applicable provision governs.

A plumbing contractor's license is held by the business, while the journeyman/master certificate is held by the individual; work must be performed by or under the direct supervision of a licensed individual.

Most jurisdictions require the licensed contractor to pull the permit; homeowners may obtain owner-builder permits only for their own primary residence, not for resale or rental property.

A stop-work order halts all work except measures needed to make the site safe; proceeding after a stop-work order is a violation independent of the original defect.

Code officials may approve alternative materials or methods when they are equivalent in quality, strength, effectiveness, fire resistance, durability, and safety.

Licenses and certificates typically renew on a fixed cycle (commonly 2 years) with continuing-education hours required; lapsed licenses cannot legally contract or pull permits.

Fixture unit (f.u.): a dimensionless measure of the load a fixture imposes; a water closet = 4 f.u. (drainage) and 2.5 f.u. (supply, private), a lavatory = 1 f.u.

Air gap is the only non-mechanical backflow method that is not subject to failure; minimum gap is the larger of 1 inch or twice the effective opening of the supply pipe.

A fixture must be constructed of approved, corrosion-resistant, non-absorbent material with a smooth interior; it must be accessible for cleaning and have a water-sealed trap.

Water closet types: gravity-tank, flushometer-tank, flushometer-valve, and electromechanical; flushometer-valve fixtures require a minimum 1-inch supply and adequate pressure (commonly 15-25 psi flowing).

Fixture spacing: water closets must have at least 15 inches from the centerline to any side wall and 30 inches of clear width; lavatories need at least 4 inches of clearance from a side wall to the centerline.

Floor drains must have a trap with a minimum 2-inch outlet and a removable strainer; trap seal primers are required where the seal could evaporate.

Each fixture must be individually trapped except where a single trap serves a set of fixtures with a continuous waste and the fixtures are within the code's distance limit.

Backflow-prevention devices on fixtures: a hose-bibb connection requires a vacuum breaker; a sill cock is a hose bibb with an integral vacuum breaker.

Residual pressure: minimum 8 psi (some codes 15 psi) at the fixture during peak flow; static pressure above 80 psi requires a pressure-reducing valve.

Sizing steps: assign fixture units, apply the probability-of-simultaneous-use table to get demand in gpm, then select pipe size from velocity and friction-loss tables (target velocity 5-8 fps).

Developed length = actual pipe length + equivalent length of fittings; add the equivalent length of each elbow, tee, and valve before using friction tables.

A water service pipe must be at least 12 inches (some codes 18 inches) below grade and separated from the building sewer by at least 12 inches horizontally, with the water above the sewer.

A full-open valve must be installed on the discharge side of the water meter and at the base of the water-heating equipment; a check valve is required where backflow is possible.

Thermal expansion: a closed system with a backflow preventer or check valve requires a thermal expansion tank sized to the heater volume and temperature rise.

Hot water distribution: a tempering valve or thermostatic mixing valve limits delivery to fixtures to 120°F; the water heater thermostat is normally set to 120-140°F.

Minimum pipe sizes: 3/4 inch for a water service, 1/2 inch for a single fixture branch, 3/4 inch for a flushometer-valve water closet branch.

Slope: 2-inch pipe = 1/4 inch per foot; 3-inch = 1/8 inch per foot minimum; 4-inch and larger = 1/8 inch per foot; uniform slope avoids solids deposition.

A trap seal must be 2 to 4 inches deep; a trap must be self-cleaning and have a developed length from the fixture outlet to the vent not exceeding the code limit.

A vent must rise vertically at least 6 inches above the fixture's flood-level rim before it can run horizontally; a vent must terminate at least 6 inches above the roof and 10 feet from an operable window or air intake.

A wet vent may serve only fixtures in the same bathroom group and must be at least 2 inches in diameter; a horizontal wet vent requires the drain to be at least 2 inches and the vent to be at least 1-1/2 inches.

A building drain is the lowest piping that receives waste inside the building; the building sewer runs from the building wall to the public sewer or private disposal system.

A cleanout is required at the base of each stack, at each change of direction greater than 45 degrees, at the building sewer, and at intervals not exceeding 100 feet (some codes 50 feet).

A backwater valve is required on a building drain where the public sewer may surcharge above the level of the lowest fixture; the valve must be accessible for service.

A vent stack must extend full size through the roof; a stack vent may serve as the vent for a soil stack, and the vent must be at least 1-1/4 inches in diameter.

Roof drains are sized by the 100-year, 1-hour rainfall intensity for the location, the roof area, and the number and size of leaders/conductors; a secondary (emergency) drainage system is required for roofs over a set area.

Storm drainage must not connect to the sanitary drainage system; combined systems are permitted only where the public system is combined and the code allows it.

A trap on a roof drain or area drain must be protected from evaporation by a trap seal primer; a roof drain must have a strainer and a sump.

Indirect waste: a fixture such as a food-service sink, sterilizer, or water-cooled condenser must discharge through an air gap or air break into a receptor, never directly connected.

Grease interceptors are required for food-service establishments; they must be sized by fixture capacity and flow rate, accessible for cleaning, and have a minimum 2-inch outlet.

A sump pump discharge must not connect to the sanitary sewer; it discharges to grade or a storm system, and the pump must have a check valve and a removable cover on the pit.

A sewage ejector pit must be vented to the building's vent system and have a gas-tight cover; the discharge must have a check valve and a gate valve.

A chemical waste system requires acid-resistant piping (e.g., polypropylene, glass, or high-silicon iron) and an approved dilution or neutralization tank before discharge.

Copper: soldered joints use lead-free solder with flux; brazed joints use a filler metal above 840°F; press fittings require a calibrated press tool and the manufacturer's insert depth.

PEX: connections use a crimp ring, a clamp ring, or a compression fitting; the pipe must be protected from UV light and supported at intervals of 32 inches horizontally (code varies).

PVC: solvent cement joints require primer, a full coat of cement, a quarter-turn assembly, and a minimum cure time that increases with pipe diameter and temperature.

ABS uses a one-step cement (no primer required in most codes); CPVC uses a different cement than PVC and must not be interchanged.

Cast iron: hubless couplings use a neoprene sleeve and stainless-steel bands; no-hub joints must be torqued to the manufacturer's specification.

Support spacing: horizontal PVC at 4 feet for 1-inch and smaller, cast iron at 5 feet per story, copper at 6 feet for 1-inch; vertical stacks must be supported at each floor.

Dielectric unions or insulating couplings are required between dissimilar metals (copper and steel) to prevent galvanic corrosion.

Underground piping must be bedded in compacted sand or select fill; thrust blocks or restrained joints are required at changes of direction on pressurized mains.

Total drainage fixture units = sum of each fixture's f.u. rating; convert to pipe size using the horizontal or vertical fixture-unit table, not by adding pipe areas.

Water supply demand: fixture units converted to gpm via the probability curve (e.g., 1 f.u. ≈ 1 gpm at low counts, but the curve flattens at high counts).

Pipe volume: gallons = 0.7854 × D² (inches) × length (feet) ÷ 231 × 1728, or use gallons per foot (1-inch pipe ≈ 0.0429 gal/ft).

Slope: fall (inches) = length (feet) × slope (inches per foot); a 60-foot run at 1/4 inch per foot falls 15 inches.

Tank sizing: drawdown gallons = tank volume × (precharge pressure relationship); use Boyle's law P1V1 = P2V2 to size a thermal expansion or pressure tank.

Rain load: roof area (sq ft) × rainfall intensity (in/hr) ÷ 96 ≈ gpm of storm flow for a 1-hour storm.

Fixture-unit values for common fixtures: water closet 4, urinal 4 (or 2 for a low-flow), lavatory 1, bathtub 2, shower 2, kitchen sink 2, washing machine 2, floor drain 1.

Water heater recovery: gallons per hour = input BTU/hr × efficiency ÷ (8.33 lb/gal × temperature rise °F).

Backflow is either backpressure (downstream pressure exceeds supply) or backsiphonage (negative pressure in the supply); the device must match the hazard.

Air gap: highest protection, no mechanical parts; used for high-hazard connections such as a boiler feed or a sewage-connected fixture.

Reduced-pressure-zone (RPZ) assembly: protection against both backpressure and backsiphonage; requires annual testing by a certified tester and must be testable in place.

Double-check-valve assembly: for low-hazard connections only; not permitted for high hazard because it has no relief valve.

Pressure vacuum breaker: for backsiphonage only, must be installed at least 12 inches above the highest downstream outlet; not for backpressure.

Atmospheric vacuum breaker: for backsiphonage only, must be installed at least 6 inches above the highest downstream outlet and cannot be under continuous pressure.

A hose bibb vacuum breaker is a field-installable device on a threaded sill cock; it must not be installed where it is under continuous pressure for more than 12 hours.

Cross-connections must be eliminated or controlled by an approved device; the water purveyor may require a containment device at the meter and annual testing records.

Confined-space entry requires a permit, atmospheric testing for oxygen (19.5-23.5%), LEL, H2S, and CO, a standby attendant, and retrieval equipment before entry.

Trench safety: spoil pile at least 2 feet from the edge, a ladder every 25 feet of lateral travel, and shoring or sloping for trenches 5 feet or deeper.

Soldering safety: remove all water and vent the pipe before heating; flux and lead-free solder fumes require ventilation, and a fire watch is required for hot work.

Lockout/tagout: isolate and tag the energy source (electrical, gas, water) before servicing; verify de-energization with a tester, and only the person who applied the lock removes it.

PPE: safety glasses for cutting and soldering, gloves for solvent cement and cast iron, hearing protection for threading and coring, and a respirator for sewer gas or lead dust.

Ladder safety: 4-to-1 rule (base 1 foot out per 4 feet of height), extend 3 feet above the landing, and maintain three points of contact.

Hand and power tool rules: keep guards in place, use the right blade for the material, and never carry a tool by its cord; inspect cords for damage before use.

Jobsite housekeeping: cap open drains and pipes, keep solvent cements and primers in a ventilated area away from flame, and mark open trenches and holes.