MN Plumber cheat sheet

Plumbing work must be performed by a licensed master or journeyman plumber, or by an apprentice under direct supervision; permits are required before installing, altering, or replacing a plumbing system.

A permit is generally not required for minor repairs such as clearing stoppages, replacing a faucet washer, or replacing a toilet tank flapper; replacing a water heater or repiping requires a permit.

Inspections occur in stages: rough-in (before concealment), water and drainage testing, and final inspection after fixtures are set and trim is complete.

Concealed work must be tested and approved before covering; the code official may require removal of covering installed before inspection at the installer's expense.

Licenses are issued by the state or local authority, carry an expiration date, and require continuing education hours for renewal; unlicensed contracting is a misdemeanor with fines.

A contractor must carry a bond and liability insurance; bonding protects the public against incomplete or defective work and code violations.

Code editions are adopted by reference with local amendments; the stricter provision governs when local amendments conflict with the model code.

Plans and specifications for commercial projects must be submitted for plan review by a licensed engineer or architect before a permit is issued.

Stop-work orders may be issued for work without a permit, unsafe conditions, or deviations from approved plans; work resumes only after the order is lifted.

Potable water is water free from impurities in amounts sufficient to cause disease or harmful physiological effects, meeting the primary and secondary drinking water standards.

A fixture unit (f.u.) is a measure of the probable discharge load of a fixture; 1 f.u. equals 1 cubic foot per minute (7.5 gpm) of flow or 1 gallon per minute of drainage load, depending on the table used.

A stack is a vertical drainage pipe carrying waste; a vent stack serves the drainage stack, and a stack vent is the extension of a drainage stack above the highest fixture branch.

A branch is a pipe between a fixture and a stack, main, or branch; a main is the primary pipe carrying water or drainage to the sewer or from the water main.

Building drain receives discharge inside the building and connects to the building sewer at a point 2 feet outside the building wall.

A plumbing system includes water supply, fixtures, drainage, venting, traps, and the building sewer; all must be designed for gravity flow and adequate venting.

Minimum slope for horizontal drainage: 1/4 inch per foot for pipe 2-1/2 inches and smaller, 1/8 inch per foot for 3 inches and larger (or per local amendment).

Water supply design uses demand load from fixture units converted to gallons per minute; the system must maintain minimum residual pressure at the highest fixture, typically 8 psi for flush tanks and 15 psi for flushometers.

The plumbing code requires protection against freezing, structural damage, and contamination; piping must be supported, sleeved through masonry, and isolated from corrosive soils.

Water closets are rated in gallons per flush (gpf): 1.6 gpf maximum for standard tanks, 1.28 gpf for high-efficiency models; urinals are 1.0 gpf or less.

Fixture clearances: water closets require 15 inches from centerline to side wall and 30 inches of clear width; 21 inches of clearance from the front of the fixture to an obstruction.

Shower compartments require a minimum of 900 square inches of interior area and 30 inches minimum dimension; shower valves must be pressure-balancing or thermostatic anti-scald type.

A water heater's temperature and pressure relief (T&P) valve must be rated for the heater's input and discharge to a safe location, terminating 6 to 24 inches above the floor or outside.

Water heaters must be installed with seismic strapping (two straps, upper and lower third) where required, and a drip pan when leakage could cause damage.

Expansion tanks are required on closed systems to absorb thermal expansion; the tank is sized to the system volume and temperature rise.

Fixture fittings must be listed and labeled; backflow protection is required at hose bibs, sill cocks, and any connection that could allow contamination.

Water heater flue connections must maintain proper draft; the vent connector rises toward the chimney and the heater needs combustion air from the space or outside.

Minimum water service size is typically 3/4 inch for a single dwelling; size depends on fixture-unit demand and developed length of pipe.

Pressure-reducing valves are required when street pressure exceeds 80 psi; 50 to 60 psi is the typical target for a residence.

Water supply pipe sizing uses fixture-unit tables converted to gpm; velocity should not exceed 8 fps in cold water and 5 fps in hot water to limit noise and erosion.

Thermal expansion of hot water lines requires allowance for movement; plastic pipe expands about 1 inch per 100 feet per 10 degrees F temperature change.

PEX and CPVC require protection from UV and freeze; copper requires dielectric unions at steel connections to prevent galvanic corrosion.

Water distribution systems must be tested at working pressure for at least one hour; hydrostatic test pressure is typically 100 psi or system working pressure.

A water main must be at least 10 feet horizontally from a building sewer or 18 inches below it when crossing, per typical separation requirements.

Hot water distribution should minimize dead legs; recirculation lines or point-of-use heaters reduce wait time and waste.

Backflow preventers are required at the service entrance when a private well, irrigation system, or boiler is connected.

Drainage pipes must be sized by fixture units and slope; a 3-inch building drain at 1/8 inch per foot carries about 40 fixture units, while 4-inch carries about 180.

Vent stacks must extend at least 6 inches above the roof and be sized per drainage stack size; a 1-1/2 inch vent stack is minimum for most dwellings.

Each trap requires a vent; a fixture may be wet-vented only where the code allows and within specified distance limits.

Horizontal drainage branch length from trap to vent is limited (typically 5 feet for 1-1/2 inch, 6 feet for 2 inch, 8 feet for 3 inch).

A cleanout is required at the base of each stack, at the building drain near the sewer, and at changes of direction greater than 45 degrees.

Drainage fittings must be directional (sweep fittings); sanitary tees are used on vertical-to-horizontal changes, wyes on horizontal-to-horizontal.

The building drain must be tested with water or air before concealment; a 10-foot head of water or 5 psi air is typical.

Vent terminals must be at least 10 feet from windows or air intakes and 3 feet above roof penetrations within 10 feet.

A combination waste and vent system is permitted only for specific fixtures and must be sized with the drain serving as the vent.

Storm drainage must be separate from sanitary drainage; combined systems are allowed only where the public sewer is combined and the authority approves.

Roof drains are sized by roof area and rainfall intensity (inches per hour); the design storm is specified by local code.

A 4-inch roof drain leader at 1/8 inch per foot carries roughly 180 fixture units or about 4,000 square feet of roof at 1 inch per hour.

Secondary (overflow) roof drainage is required where the primary system could be blocked; scuppers or secondary drains must discharge to a visible location.

Storm drainage may not discharge into the sanitary sewer unless approved; it must go to a storm sewer, dry well, or approved dispersal area.

Leader and storm drain pipe must be supported and protected from freezing; cleanouts are required at the base of leaders and at changes of direction.

Sizing tables use the roof area and rainfall rate to determine leader and horizontal storm drain diameter; steeper slopes increase capacity.

Sump pumps and area drains must discharge to an approved location and cannot connect to the sanitary sewer without approval.

Storm drainage systems require testing similar to sanitary systems; water test or smoke test may be used.

Each fixture must have a trap with a liquid seal of 2 to 4 inches; trap arms must be protected from siphonage by venting.

A trap may serve one fixture only; except for a set of fixtures with a continuous waste, or a floor drain and its trap primer.

Grease interceptors are required for commercial kitchens; sizing is by fixture units or by the formula: capacity = gallons per minute of flow times retention time.

An interceptor must be installed with a vent, cleanout, and accessible cover; the flow-through rate and grease retention capacity are listed on the interceptor.

Sand and oil interceptors are required for garages, service stations, and car washes; they must be cleaned and maintained by the owner.

A trap primer is required for floor drains that could lose their seal; a trap seal must be maintained to prevent sewer gas entry.

Special wastes such as chemicals, acids, and photographic wastes require neutralization or dilution before discharge, per local pretreatment rules.

A backwater valve is required on fixtures below the sewer grade where backflow could occur; it must be accessible for maintenance.

Trap arms must be level or have a grade, must not exceed the developed length allowed, and must be vented within the allowed distance.

Fuel gas piping must be sized by the longest length method or the branch length method using the gas code tables; the sizing depends on gas type, pressure, and total load.

Natural gas is supplied at about 1,000 Btu per cubic foot; propane is about 2,500 Btu per cubic foot, so pipe sizes differ for the same appliance load.

A shutoff valve is required within 6 feet of each appliance and must be accessible; a union or flanged connection is required at the appliance.

A sediment trap (drip leg) is required at the appliance connection for gas-fired appliances to catch debris before it enters the controls.

Combustion air must be provided by the appliance manufacturer's instructions and the gas code; two permanent openings to an interior space are typical.

Gas piping must be tested at 1.5 times the working pressure, but not less than 3 psi for a 10-minute test on low-pressure systems (or as the code specifies).

Gas vents must terminate above the roof, with clearances to windows, doors, and air intakes; a vent must not terminate in a crawl space or attic.

Flexible appliance connectors must be listed, not concealed in walls, and not exceed 6 feet in length unless the manufacturer allows otherwise.

Gas piping cannot be installed in a concealed location without protection, and it must be supported at intervals specified by the code.

Backflow is the reversal of flow in a water system; it can be caused by backpressure or backsiphonage.

An air gap is the only absolute backflow protection; an RPZ (reduced pressure zone) assembly is required for high-hazard connections.

A double check valve assembly is used for low-hazard connections; a pressure vacuum breaker is used for irrigation systems.

Backflow assemblies must be tested annually by a certified tester; test reports are submitted to the water authority.

Water conditioning includes softening, filtration, and disinfection; softeners use ion exchange and must be installed with a bypass and drain to an approved location.

Cross-connections must be eliminated or protected; a hose bib is a common cross-connection and requires a vacuum breaker.

Potable water systems must be protected from contamination by chemicals, sewage, and process water; separation distances between water and sewer lines must be maintained.

Lead and copper concerns require corrosion control; water treatment must not create a health hazard or exceed contaminant levels.

A backflow prevention device must be accessible for testing and maintenance and installed in the orientation required by the manufacturer.

A floor plan shows fixture locations and pipe routing in plan view; a riser diagram shows vertical relationships and stack connections.

An isometric drawing shows three dimensions (width, height, depth) on a 30-degree angle grid; pipe lengths must be calculated from the true lengths of runs.

Developed length is the total length of pipe plus fittings measured along the centerline; fitting allowances are added for each 90-degree or 45-degree turn.

A 45-degree offset length equals the offset times 1.414; a 22-1/2 degree offset uses a multiplier of 2.613.

Fixture-unit calculations sum each fixture's f.u. value; convert to gpm using the demand curve for sizing water supply.

Material takeoff: count fittings, pipe lengths, and valves from the isometric, then add a waste factor (typically 5 to 10 percent).

Pipe grade is expressed as inches per foot; total fall equals slope times run length (e.g., 1/4 inch per foot over 20 feet equals 5 inches).

A plumbing plan must show the building drain, building sewer, vents, water service, and fixture locations; dimensions and elevations are taken from the plan.

Scale is read from the drawing title block; measure with a scale and convert to actual dimensions before ordering material.