DC Plumber flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

DC Plumbing Code adoption

The District of Columbia adopts the International Plumbing Code as its plumbing code, with local amendments in the DC Construction Codes Supplement that take precedence where they conflict with the model text.

Permit expiration period

A plumbing permit expires if work does not begin within 180 days of issuance or if work is suspended or abandoned for 180 days. Extensions must be requested in writing before expiration.

Water closet clearance

Code requires at least 15 inches from the centerline of a water closet to any side wall or partition, and a minimum 30-inch-wide clear space for the fixture.

Rough-in inspection timing

Rough-in plumbing must be inspected after piping is installed but before it is concealed by wall, floor, or ceiling finishes. Covered work must be exposed for re-inspection.

Static pressure per foot

Static water pressure increases 0.433 psi for every foot of elevation drop, equivalent to 2.31 feet of water column per psi. A 10-foot drop adds about 4.33 psi.

Trap seal depth

A trap seal is the vertical distance from the trap weir to the top of the trap dip, typically 2 to 4 inches. The seal prevents sewer gas from entering the building.

Drain slope rule

Horizontal drainage pipe is installed at 1/4 inch per foot for sizes 2 1/2 inches and smaller, and 1/8 inch per foot for 3-inch and larger pipe, to maintain scouring velocity.

Vent purpose

A vent equalizes air pressure on both sides of a trap seal, preventing siphonage and backpressure from pulling the seal and allowing sewer gas into the building.

Lead-free definition

For potable water, lead-free means the weighted average lead content of the wetted surface of pipe, fittings, and solder does not exceed 0.25 percent.

Copper tube types

Type K copper is thickest and used underground; Type L is standard; Type M is thin wall for above-ground use and is not permitted underground.

No-hub coupling torque

Cast iron no-hub couplings must be tightened to the manufacturer's specified torque using a calibrated torque wrench; over-tightening can crack the pipe or deform the gasket.

Water closet flush rating

Tank-type water closets are limited to 1.6 gallons per flush, and urinals to 1.0 gallon per flush, under federal and DC conservation requirements.

Flushometer residual pressure

A flushometer valve requires at least 20 psi residual pressure at the fixture outlet during flow; sink faucets need 15 psi and other fixtures 8 psi minimum.

Pressure-reducing valve threshold

When static water pressure exceeds 80 psi, an approved pressure-reducing valve with a strainer must be installed and made accessible for service and adjustment.

Thermal expansion tank

A closed water system with a backflow preventer or pressure-reducing valve needs a thermal expansion tank to absorb pressure rise as heated water expands.

Fixture unit sizing

Water supply pipe is sized using fixture unit tables that assign demand values to fixtures, then matched to pipe capacity based on length and pressure available.

Trap arm length limit

The developed length of a trap arm is limited to 42 inches for 1 1/2-inch pipe, 60 inches for 2-inch pipe, and 72 inches for 3-inch pipe.

Vent terminal height

A vent terminal must extend at least 6 inches above the roof and be at least 10 feet from or 2 feet above any window, door, or outdoor air intake.

Building drain definition

The building drain is the lowest piping that receives soil and waste inside the building; it becomes the building sewer 30 inches outside the building wall.

Cleanout locations

Cleanouts are required at the base of each stack, at the building sewer, at direction changes greater than 45 degrees, and at intervals not exceeding 100 feet of horizontal drain.

T&P relief discharge

The temperature and pressure relief valve discharge pipe must terminate within 6 inches of the floor, be the same size as the valve outlet, and not connect to the drainage system.

Water heater drain pan

A drain pan is required under a water heater where leakage would cause damage; the pan must be at least 1 1/2 inches deep with a drain to an approved location.

Anti-scald shower valve

Shower and tub valves must have anti-scald protection that limits hot water delivery, commonly to 110°F at public lavatories and bathtubs to prevent burns.

Trap primer requirement

Floor drains and other infrequently used traps require a trap primer to maintain the seal, and the primer connection must be protected against backflow.

Gas piping test pressure

Gas piping is tested with air or inert gas at not less than 1 1/2 times the working pressure and at least 3 psi, held for the code-required duration before inspection.

Gas sediment trap

A sediment trap must be installed downstream of the appliance shutoff valve to capture debris before it reaches the gas controls and burner orifices.

Gas appliance shutoff

A listed shutoff valve must be installed within 6 feet of the appliance, be accessible, and be provided with a union or approved disconnect for appliance removal.

Combustion air openings

Gas appliances in confined spaces require two permanent openings sized per code, or a direct-vent arrangement, to supply adequate combustion air and prevent incomplete combustion.

Air gap sizing

An air gap must be at least twice the diameter of the supply pipe and never less than 1 inch above the flood-level rim of the receiving fixture.

RPZ assembly use

A reduced pressure zone assembly protects against both backsiphonage and backpressure for high-hazard connections and requires installation testing plus annual certification.

Vacuum breaker height

A pressure vacuum breaker protects against backsiphonage only and must be installed at least 12 inches above the highest downstream outlet or flood-level rim.

Trench protective system

Trenches 5 feet or deeper require shoring, sloping, or a trench box, and 811 must be called for utility locates before any excavation begins.