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; typically 1.5x working pressure for 15 min.

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