Bluegrass Plumb Line

• 318.010 — Definitions. Know "plumbing," "master plumber," "journeyman plumber," "apprentice."
• 318.020 — Exemptions: apprentices working under supervision, maintenance men, water company/district employees.
• 318.030 — License required to engage in the plumbing trade; masters must also carry general liability insurance.
• 318.040 — Qualifications, examinations, reciprocity.
• 318.050 / .054 — Fees; licenses expire on your birth month; renewal requires continuing education.
• 318.060 — Reexamination after a failure.
• 318.064 / .066 — License revocation/suspension; hearings and appeals.
• 318.080 — State Plumbers Examining Committee.
• 318.090 / .140 — Plumbing inspectors; local governments enforce the State Plumbing Code.
• 318.120 — Employing an unlicensed plumber is prohibited.
• 318.130 — The Department of Housing, Buildings and Construction adopts the State Plumbing Code by regulation.
• 318.134 — Installation permits: required before plumbing is installed; know who obtains them and when. Master-exam favorite.
• 318.160 — Installation plans and specifications.
• 318.200 — Water heating devices and serial numbers.

The licensing regulation — the exam facts on the first tab come from here. Memorize: journeyman needs 2 consecutive apprentice years (or approved course + 1 year); master needs a journeyman license 2 of the preceding 5 years; journeyman passes at 75%, master at 80%; exams run quarterly; applications due 3 weeks ahead.

• Permit required for: new installations, relocated fixtures, replaced house sewers or water services, backflow preventers, and new or replaced water heaters.
• No permit needed for: repairing leaks, cocks, and valves, or cleaning waste pipes.
• Who can pull one: a licensed master plumber — or a homeowner who applies before starting, files a compliance affidavit, does the work personally, and hasn't held a homeowner permit in the past 5 years.
• Fees (since 3/1/2022): residential $50 base + $14 per fixture/opening; commercial $50 base + $20 per fixture/opening/conductor; water-heater-only permit $50 flat.
• Five inspections included; additional inspections $50 each (waived if the permit cost over $250).
• Permits expire after one year unless construction is ongoing; void if work stops 12+ months.

• Developed length — length measured along the center line of pipe and fittings. Trap-arm and vent limits are developed length.
• Fixture unit — the code's load measure for drainage and supply; roughly 7½ gal/min (1 cu ft/min) of discharge.
• Soil pipe vs. waste pipe — soil pipe carries discharge from water closets/urinals (fecal matter); waste pipe carries other fixture discharge.
• Stack — the vertical main of a soil, waste, or vent system. Stack vent = the extension of a soil/waste stack above the highest horizontal drain. Vent stack = a vertical pipe installed purely to provide air circulation.
• Building (house) drain — lowest horizontal piping inside the building; it becomes the building sewer 2 feet outside the building wall. That 2-foot line is a favorite test question.
• Trap arm — the portion of the fixture drain between the trap and its vent.
• Branch interval — a story height along a stack, but never less than 8 feet.
• Horizontal vs. vertical pipe — horizontal is less than 45° from horizontal; vertical is 45° or less from vertical.
• Hot water — water at not less than 120°F.
• The vent family — individual, branch, common (junction of two fixture drains), continuous, circuit (2+ traps to a vent stack), loop (same but back to the stack vent), relief (extra air circulation), and yoke (stack-to-vent-stack, relieves pressure in tall stacks). The exam loves telling these apart.
• Air break — indirect discharge below the flood level rim (the air gap is above it).
• Critical level — how deep a vacuum breaker can be submerged before backflow; if unmarked, the bottom of the device.
• Trap seal — the water in a trap between dip and crown weir that blocks sewer gas.
• Air gap — unobstructed vertical distance between a supply outlet and the flood-level rim.
• Cross-connection / backflow — any link between potable and non-potable water; the code exists to prevent it.
• Wet vent — a vent that also serves as a drain for other fixtures.

• Overflows are optional — but if used, they connect to the inlet side of the trap and stay accessible for cleaning.
• Traps and pipes stay at least 12″ off the floor (laundry trays excepted); pipes run to the wall.
• Water closets: one-piece bowls with integral flushing rims; max 1.6 gal/flush residential, 3.5 gal/flush commercial.
• Showers: pans turn up the walls at least 6″; heads flow at most 2.5 gpm.
• Floor/shower drains are fixtures; strainer outlet area ≥ the trap's interior area.
• 20:191 — minimum fixture counts: every dwelling unit gets at least one water closet, one lavatory, and one bathtub or shower. Employee facilities are separate by sex when more than 5 employees work in the building. Dormitories: 1 WC per 10 persons. Schools: at least 2 water-bottle filling stations plus one fountain per 75 students; fountain orifices sit 1″ above the overflow rim with a protective cowl.

• A/C condensate (evaporative coolers, air handlers) is never directly connected to soil, waste, or vent piping — indirect waste through an air gap into a floor drain or approved receptor.
• Commercial laundries: at least a 4″ trap with full-size vent; semicommercial machines share a 4″ waste/trap with max 2 machines, counted as 4 FU.
• Flammable waste (gasoline, benzine, naphtha) discharges through a separator before the sanitary sewer, vented with a 3″ vent.
• Garage sand traps: concrete, minimum 2′ × 4′, 10″ from outlet to trap bottom, 4″ vent.
• Pedicure chairs: up to 2 chairs → 2″ receptacle; 3–6 chairs → 3″ minimum; high-hazard setups need RPZ backflow preventers on hot and cold supplies.

• Installers must be BOTH a certified medical gas installer per NFPA 99 AND a licensed master or journeyman plumber.
• Installations follow NFPA 99 (Health Care Facilities Code) — incorporated by reference.
• The supervising master plumber verifies installer qualifications, proper products and storage, requests inspection at the initial pressure test, and submits the system verifier's certification to the division at completion.
• Permit: $50 per building + $20 per opening.

• Every home gets a 4″ sewer; the home's waste connection to it is at least 3″.
• Branch sewers by community size: 1–10 homes → 4″ · 11–20 → 5″ · 21–50 → 6″ · 51–150 → 8″ · 151–300 → 10″.
• Water services by count: 1–2 homes → ¾″ · 3–6 → 1″ · 7–12 → 1¼″ · 13–20 → 1½″ · 21–50 → 2″ · 51–100 → 3″.
• Water risers terminate ≥ 4″ above ground with a ¾″ valve, encased in 8″ vitrified clay pipe (or equal) packed with insulation against freezing.
• Piping with less than 18″ of cover must be cast iron.

• Lead pipe is prohibited in potable water systems. Approved: copper, CPVC, PEX, galvanized steel (water); cast iron, PVC/ABS Schedule 40/80, copper (drainage).
• PVC/ABS height limit: buildings not exceeding 45 feet (applies to DWV and storm conductors).
• Horizontal support spacing: copper ≤1″ → 6′, ≥1¼″ → 10′ · steel ≥1½″ → 12′, ≤1¼″ → 8′ · PVC/ABS → 4′ · CPVC ≤1″ → 3′ · PEX ≤1″ → 32″, ≥1¼″ → 48″.
• Vertical: copper 1½″+ at each story; screwed steel every other story.
• Joints: unions ground-faced and never concealed; no fittings with enlargement chambers or ledge shoulders in drainage.
• Storage: PEX away from UV and petroleum; solvent cement away from ignition and never past shelf life; plastic pipe lifts stacked max 3 high.

Minimum trap and branch sizes per fixture — these are pure memorization and show up in both the written and drawing portions. The core table is in the Pipe Sizing tab. Anchors: lavatory 1¼″ · tub, shower, kitchen sink 1½″ · clothes washer 2″ · water closet 3″ · floor drain 3″ (industrial 4″).

• Traps: every fixture individually trapped, as near the fixture as possible — max 10″ vertical from fixture outlet to the trap's seal dip. Water seal at least 2″, no more than 4″.
• Trap-to-vent distance: every trap needs a vent within a maximum developed length that depends on drain size (e.g., 1½″ drain → 3′6″; 4″ drain → 10′). Full table in Pipe Sizing.
• Vent sizing: tables give maximum fixture units and maximum developed length per vent diameter (e.g., 1¼″ vent → 2 FU; 3″ vent → 72 FU at up to 300′).
• Stacks: soil and waste stacks extend full size through the roof, minimum 3″ where they pass through, terminating at least 1′ above the roof — 5′ where the roof is a deck/promenade; 2′ above any window or door within 10′ (unless screened); increasers go at least 1′ below the roof.
• The water closet rule: max 3 standard WCs per 3″ soil pipe (4 if all are 1.6 gpf); WC fixture branch no longer than 4′6″.
• Grade: horizontal drainage runs at a uniform grade of at least 1/8″ per foot.
• Cleanouts: max 150′ apart in sewers; at the base of each stack where stacks exceed 45′; same nominal size as the pipe they serve (within limits); accessible.
• Prohibited traps (basic principles): S-traps, bell traps, crown-vented traps, traps depending on moving parts.

• Water service: minimum ¾″ from the main to the building, sized for continuous, ample flow.
• Distribution: hot and cold mains minimum ¾″ to the first branch; no more than three ½″ fixture branches on one ½″ line; concealed branches minimum ½″.
• Backflow protection: the air gap is the best protection in all situations. Minimum gaps run from 1″ (lavatories) to 3″ (bath fillers near walls). RPZ (reduced pressure zone) assemblies must be tested at least annually.
• Cross-connections: private water supplies may never be interconnected with a public supply.
• Thermal expansion: where a check valve closes the system, install a thermal expansion tank (or other relief) on the cold supply near the water heater.

• T&P relief valve on the hot side, within 3″ of the top of the heater — full-size drain, never trapped or valved off.
• Discharge: with a floor drain, pipe to within 2″ of the floor; without one, pipe outside with an ell turned down, within 4″ of the ground.
• Tankless (instantaneous): relief valve rated no more than 150 psi.
• Space heating combo: water temperature max 140°F; above 210°F the unit falls under KRS 236 pressure-vessel rules.
• Pans: attic, drop-ceiling, or wood-floor installations (post-4/1/2021) need a corrosion-resistant watertight pan with at least a ¾″ drain.
• Heaters stay accessible for inspection, repair, and replacement. KRS 318.200 covers serial numbers.

• Minimum house sewer: 4″, and never smaller than the house drain it serves.
• Grade: between 1/8″ and 1/4″ per foot — too steep is a violation too (solids get stranded). A classic exam trap.
• Cover: 18″ minimum; 24″ under driveways/parking unless approved pipe encased in concrete.
• Materials: cast iron, vitrified clay, concrete, PVC/ABS, truss, PE (per ASTM). Inside storm conductors: cast iron, galvanized steel, copper, or approved plastic — plastic limited to buildings ≤ 45′.
• Storm sizing: roof area at a 4″-per-hour rainfall baseline.
• Trench stays open for inspection; backfill hand-tamped to 6″ above the pipe.

• Rough-in inspection before anything is concealed; final inspection at completion. The permit holder requests both.
• Alterations/repairs involving more than 10′ of soil, waste, or vent piping require inspection.
• Water test: by sections with at least a 10′ head; whole system filled to overflow. Water distribution tests at max working pressure.
• Rough air test: 5 psi held 15 minutes.
• Final air test: 1″ water column, 15 minutes, on the entire soil-waste-vent system including fixtures — everything except the house sewer.

1. Identify every fixture on the drawing and assign its fixture-unit (FU) load from the table.
2. Size each fixture branch and trap from the minimum-size table — these are fixed minimums, no math.
3. Work downstream: total the fixture units at each horizontal branch and each stack section, and size from the FU-capacity table. A pipe never gets smaller in the direction of flow.
4. Check the special rules: any stack serving a water closet is at least 3″; stacks run full size through the roof (3″ minimum at the roof, 1′ above it); no drain smaller than its trap.
5. Size the vents: every trap vented within its distance limit; vent size from the vent table (diameter vs. FU served vs. developed length).

• Soil/waste stacks: full size through the roof, 3″ minimum at the roof, terminate ≥ 1′ above it — but ≥ 5′ where the roof is used as a deck or promenade.
• A vent terminal within 10′ of a window or door must extend 2′ above the opening's top edge (unless screened).
• A stack smaller than 3″ increases to 3″ with the increaser fitting at least 1′ below the roof.
• Horizontal drainage piping: uniform grade, minimum 1/8″ per foot.
• Trap seal 2″–4″; fixture outlet to trap dip ≤ 10″; branch interval never less than 8′.
• Cleanouts ≤ 150′ apart on sewers; at stack bases over 45′.

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