WI Plumber cheat sheet

Pressure and head: 1 foot of water column = 0.433 psi; 1 psi = 2.31 feet of head.

Water weighs 62.4 lb per cubic foot and 8.34 lb per gallon; 1 cubic foot = 7.48 gallons; 1 gallon = 231 cubic inches.

Pipe or tank volume in gallons = 0.7854 x (inside diameter in inches)^2 x length in inches / 231.

Backflow protection hierarchy: an air gap protects against both backsiphonage and backpressure; a reduced pressure zone assembly also protects against both but must be tested; a vacuum breaker protects only against backsiphonage.

Fixture unit sizing: water supply fixture units are summed along a branch and converted to probable demand in gpm from the sizing table; drainage fixture units size the drain and vent.

Trenching rule: spoil, materials, and equipment are kept at least 2 feet back from the excavation edge, and any trench 5 feet or deeper requires sloping, shoring, or a trench box with a competent person on site.

Lead restrictions: solder and flux contain not more than 0.2 percent lead, and pipe, pipe fittings, and fixtures average not more than 0.25 percent lead on wetted surfaces.

Thermal expansion: heating water from 40 F to 140 F increases its volume roughly 1.5 to 2 percent, so a closed system needs an expansion tank or a relief device.

Water hammer arrestors are installed at the end of branches serving quick-closing valves such as flushometers, solenoids, and washing machine boxes.

Design velocities: keep flow at or below about 8 feet per second in cold water lines and 5 feet per second in hot water lines to control noise and erosion.

Service lines are buried below the local frost depth; Wisconsin frost depths run roughly 3.5 feet in the south to about 6 feet in the north, so the local depth governs.

A pressure-reducing valve is required on the service when street pressure exceeds 80 psi; fixture flow pressure is normally maintained in the 20 to 80 psi range.

Residual (flowing) pressure is the pressure remaining at a fixture while water is running, and code tables set a minimum for each fixture type, commonly 8 to 20 psi.

Minimum fixture supply size is governed by code tables; no fixture supply may be smaller than the table value for that fixture type.

Backflow protection by application: hose bibbs need vacuum breakers, boiler feed and chemical connections need an air gap or RPZ, and irrigation systems need an approved backflow assembly.

Separation from drainage: water pipe must be at least 12 inches above a parallel sewer line, or separated horizontally by at least 5 feet if the vertical clearance cannot be maintained.

A full-flow shutoff valve is required on the water service at the point of entry and on each branch or fixture group so the supply can be isolated for repair.

Drainage slope: 1/4 inch per foot for pipe 2-1/2 inches and smaller; 1/8 inch per foot for pipe 3 inches and larger; flatter slopes are not permitted.

Trap seal must be 2 to 4 inches of liquid depth, and the vertical drop from the fixture outlet to the trap weir may not exceed 24 inches.

Trap arm limits by size: 1-1/4 inch = 5 ft, 1-1/2 inch = 6 ft, 2 inch = 8 ft, 3 inch = 12 ft, 4 inch = 16 ft from trap weir to vent fitting.

Vent terminals extend at least 6 inches above the roof surface, at least 3 feet from operable windows, doors, and other openings, and 10 feet from outdoor air intakes.

Cleanouts are required at the base of each stack, at the building sewer, at intervals of 100 feet in horizontal runs, and at changes of direction greater than 45 degrees.

Fixture drain minimums: water closet 3 inch, kitchen sink 1-1/2 inch, lavatory 1-1/4 inch, bathtub 1-1/2 inch, floor drain 2 inch.

S-traps, double traps, crown-vented traps, and unvented traps are prohibited; every trap must be protected by a vent taken from the trap arm.

A backwater valve is required where the building drain is below the level of the next upstream manhole or where the authority determines sewage backup is possible.

Water closet clearance: at least 15 inches from the fixture centerline to a side wall or partition, and at least 21 inches of clear space in front of the bowl.

Lavatory clearance: at least 15 inches from centerline to a side wall and at least 21 inches of clear space in front of the fixture.

Flush tank fixture units: a 1.6 gallon-per-flush water closet equals 3 water supply fixture units and 4 drainage fixture units; a lavatory equals 1 and 1.

Water heater relief: the temperature and pressure valve is set at or below the tank rating, mounted in the top 6 inches of the tank, with a full-size untrapped discharge ending 6 to 24 inches above the floor.

Dishwasher discharge must pass through an air gap or a high loop secured under the counter before connecting to the sink drain or disposer.

Floor drains and other infrequently used traps need a trap primer or an approved seal to maintain the required trap seal against evaporation.

Accessible water closets: bowl rim 17 to 19 inches above the floor, centerline 16 to 18 inches from the side wall, and clear floor space beside and in front of the fixture.

Indirect waste connections (ice machines, sterilizers, dishwashing units) discharge through an air gap into a receptor, never by direct connection to the drainage system.

Wis. Admin. Code SPS 382 governs design, construction, installation, and inspection of plumbing; SPS 384 covers plumbing products and SPS 383 covers private onsite wastewater treatment systems.

A plumbing permit must be obtained before installing, altering, or replacing piping, fixtures, or appliances, except for repairs the code specifically exempts.

Rough-in inspection occurs after piping is installed and tested but before it is covered; a final inspection is required before the system is placed in use.

Cross-connection control assemblies such as reduced pressure zone devices must be tested at least annually by a certified tester and the results filed with the water utility.

Only a licensed master plumber may obtain plumbing permits and contract for plumbing work; journeymen and apprentices must work under the required supervision.

Plans for public buildings and certain multifamily projects must be submitted for plan review and approved before a permit is issued.

Private onsite wastewater treatment systems require a soil evaluation and a state or county permit before installation or replacement.

The authority having jurisdiction may order defective work corrected, require testing, or order the water supply disconnected where a condition creates a health hazard.