Common Pipe Fittings Reference

Why this matters

Every plumbing job uses fittings. Wrong fitting type = leak; wrong size = retrofit; wrong material = corrosion + failure. The plumber who knows fittings by sight + sizes correctly finishes jobs without parts-store trips. This is the field card.

Fitting categories

Couplings: join two pipes of same diameter.

Reducers / bushings: change pipe size.

Tees: 3-way junction; main pipe + branch.

Elbows (ells): change direction; 45°, 90°, 22.5°.

Unions: serviceable joint; two pipes meet with disconnect-able middle.

Caps: dead-end seal.

Plugs: thread into a female end; seals it.

Adapters: change connection type (slip → MPT, sweat → push-fit, etc.).

Valves: shutoff, check, regulating, mixing.

Pipe sizing terminology

NPS (Nominal Pipe Size): pipe identifier; actual OD slightly different.

ID (Inside Diameter): where water flows.

OD (Outside Diameter): outside; what fittings clamp around.

Schedule: wall thickness (Sched 40, 80, etc.).

Class (cast iron): pressure rating.

Common copper fittings (sweat OR press)

Coupling: 1/2" CxC, 3/4" CxC, 1" CxC.

Reducing coupling: 3/4" × 1/2" CxC, etc.

Tee: 1/2" CxCxC, 3/4" CxCxC + reducing tees.

90° elbow: 1/2" CxC, 3/4" CxC.

45° elbow: smaller direction change.

Female adapter (FxC): copper to female pipe thread (NPT).

Male adapter (MxC): copper to male pipe thread.

Union (sweat OR press): serviceable joint.

Brass to copper adapter: brass thread + copper sweat / press.

Cap: dead-end seal.

Plug: threads into FPT.

Threaded (NPT) fittings

National Pipe Thread Taper (NPT): tapered thread sealed with pipe dope OR PTFE tape.

Male (MPT) + female (FPT): ends.

Common sizes: 1/2", 3/4", 1", 1-1/4", 1-1/2", 2".

Brass NPT: water systems.

Black iron NPT: gas systems (NEVER water; rusts inside).

Galvanized NPT: legacy water; rust + corrosion issues over decades.

Stainless NPT: corrosive environments.

PVC + CPVC fittings (slip OR threaded)

Slip fittings: smooth socket; solvent-welded with cement.

Threaded (FPT OR MPT): for transition to threaded pipe.

Reducer bushing (slip × slip): change size in same fitting.

Reducer adapter: slip × FPT OR MPT.

Sanitary tee: smooth sweep; for DWV (Drain Waste Vent).

Long-radius elbow: smooth sweep; for DWV (better flow).

Sweep tee + 1/4 bend: DWV-style elbow patterns.

Cleanout (DWV): removable plug for snaking.

PEX fittings (crimp / cinch / expansion)

Brass crimp fitting (PXP): PEX × PEX coupling.

Brass crimp PEX × Female NPT: PEX × threaded.

Crimp PEX × Sweat (rare; usually go PEX × NPT × Brass × Sweat).

Push-fit (SharkBite): no-tool installation; quick repair; expensive.

Expansion PEX-A (Uponor): PEX expands + fitting inserts; pipe shrinks back.

Brass tee, elbow, cap: standard.

Compression fittings

Brass ferrule + nut: compresses around pipe.

Common applications:

• Toilet supply (3/8" compression)
• Lav faucet supply
• Refrigerator ice maker (1/4" compression)
• Angle valve (1/2" CPVC × 3/8" compression)

Reusable: ferrule + nut can be removed + reused.

Don't over-tighten: cracks tube OR strips threads.

Quick-connect fittings

John Guest (Speedfit): push-in for RO + water filtration + ice maker.

SharkBite: PEX, copper, CPVC; emergency repair OR permanent.

Uponor ProPEX: expansion-style.

ProPress (Viega, NIBCO): copper joining without solder.

DWV (Drain Waste Vent) fittings

Sanitary tee: 90° branch with smooth sweep (waste flows down).

Long sweep 1/4 bend: 90° elbow with gradual curve.

1/8 bend (45°): directional change.

Wye + 1/8 bend: branch + flow change.

Cleanout (CO): removable plug for snaking access.

Closet flange: toilet connection to drain.

Trap: J-trap (with cleanout), P-trap (most common).

Vent T: branch off drain for vent.

Reducer: change size in DWV.

Valves

Ball valve: quarter-turn handle; full bore. Most-common shutoff. Brass body, stainless ball.

Gate valve: full-bore; older style. Slow operation. Galls + leaks over time.

Globe valve: regulating flow + throttling.

Check valve (swing OR spring-loaded): prevents backflow.

Pressure-reducing valve (PRV): residential supply pressure regulation.

Mixing valve: thermostatic; mixes hot + cold; protects against scalding.

Stop + waste: shutoff + drain (frost protection).

Angle stop / supply stop: under fixture; 1/4-turn.

Fixture fittings

Lav faucet: 1/2" sweat OR PEX adapter to supply lines.

Tub / shower valve: integrated valve assembly with rough-in box.

Toilet supply: 1/2" supply line + angle stop + 3/8" compression flex to tank.

Kitchen sink: dual 1/2" supplies + 1/4" optional ice maker.

Specialty fittings

Stub-out (wall outlet): 1/2" copper OR PEX with cap; capped during construction.

Tail piece (sink drain): chrome OR plastic; from sink down.

P-trap (sink, lav): 1-1/4" OR 1-1/2"; plastic chrome.

Tail extension: extends sink drain.

Disposal flange + tail: connects disposal to drain.

Common fitting mistakes

Wrong material (PVC water supply = code violation in most jurisdictions). Wrong thread sealant (Teflon tape too thin for gas; pipe dope wrong for some plastics). Cross-threading (forces threads + leaks). Over-torquing (cracks fitting OR strips threads). Mixing copper + galvanized without dielectric union (galvanic corrosion). Wrong reducer direction (eccentric vs concentric for DWV).

Fitting truck stock

Copper: 1/2" + 3/4" elbows, tees, couplings, caps, adapters (MxC + FxC); compression fittings; press fittings if tool carried.

PEX: 1/2" + 3/4" elbows, tees, couplings, female adapters, manifolds.

PVC: 1-1/2" + 2" DWV elbows, tees, couplings, sweeps; primer + cement.

Brass: ball valves (1/2", 3/4"), angle stops, supply lines, mixing valves.

Gas (black iron): 1/2" + 3/4" elbows, tees, couplings (separate stock; threaded).

Joining methods quick reference

Code references

Approved materials by code: PEX, copper, CPVC for water supply; PVC + ABS + cast iron for DWV; black iron for gas. Local codes vary.

Test pressure: per IPC Chapter 3, the water distribution system is proved tight at not less than the system working pressure, or (for piping other than plastic) by an air test of not less than 50 psi. Duration and witness are the code official's call. The 1.5x-design-pressure hydrostatic rule some shops quote comes from ASME B31 process piping, not from the plumbing code; do not substitute it for what the AHJ asks for.

References

• IPC + UPC plumbing codes
• ASME B16 series (fittings standards)
• Manufacturer technical data (NIBCO, Apollo, Charlotte Pipe, Watts)
• Manuall internal: Pipe Sizing Materials, Water Pressure + Flow