Pipe Fittings: Every Type, Material System & How to Order

Pipe fittings are the grammar of a plumbing system — the elbows, tees, couplings, reducers, unions, and adapters that turn straight lengths of pipe into a working network. Get the vocabulary right and ordering is precise; get it wrong and the site stalls on parts that don't fit, don't seal, or don't match the pipe material. And "fittings" is really three questions stacked together: what shape does the run need, what material system does the pipe belong to, and how does the joint actually seal? This guide answers all three — every common fitting shape and its job, how fittings differ across PPR, PVC, CPVC, PEX, HDPE, and brass, the joining methods and thread standards, sizing rules, and how to put together a complete fitting order that assembles first time.

The Fitting Shapes and What Each One Does

Whatever the material, the shape vocabulary is universal. Learn it once and every catalog in the industry reads the same way.

Fitting	What it does	Watch out for
Elbow (90°, 45°)	Changes direction	Two 45s flow better than one 90 on drainage
Tee	Adds a 90° branch	Reducing tees change the branch size
Wye (Y)	Adds an angled branch	The drainage branch of choice — smooth flow
Coupling / socket	Joins two pipes straight	Slip couplings repair without moving pipe
Reducer / bushing	Steps between sizes	Concentric vs eccentric matters on horizontals
Union	A joint you can open for service	Place at every serviceable component
Nipple	Short male-threaded link	Close nipples leave little wrench grip
Adapter	Transitions method or material	The bridge between systems — spec carefully
Cap / plug	Closes an end (cap) or port (plug)	Pressure-rate them like any fitting
Flange	Bolted joint for large lines	Match drilling pattern and gasket standard
Cross	Four-way junction	Rare in supply; check code before using

One Shape, Many Systems: Fittings by Pipe Material

Here is the rule that prevents the most expensive mistakes: a fitting belongs to its pipe's material system, not just to a size. A ¾" elbow exists in every material — but the PPR one fuses, the PVC one cements, the PEX one crimps, and none of them fits the others' pipe. Each system has its own guide on this site; the map below is the summary.

System	How its fittings join	Deep-dive guide
PPR	Heat fusion — pipe and fitting melt into one piece	PPR fittings guide
PVC / CPVC	Solvent weld — each with its own cement	PVC fittings guide
PEX	Crimp, clamp, expansion, or push-fit	PEX fittings guide
HDPE	Butt fusion or electrofusion	HDPE fittings guide
Brass	Threaded, compression, or push-fit	Brass fittings guide

Two practical consequences. First, the joining method sets your toolkit: a PPR crew carries a fusion welder, a PVC crew carries primer and cement, a PEX crew carries a crimp or expansion tool. Second, drainage and pressure fittings differ within the same material — a PVC DWV tee has flow-directing sweeps and no pressure rating, while a PVC pressure tee is built to hold it. Same material, same shape name, different part.

Threaded Fittings: BSP vs NPT, Male vs Female

Threads deserve their own section because they cross every material and cause the most silent failures. Two standards dominate: BSP (British Standard Pipe — Europe, Middle East, Asia, Africa, Australia) and NPT (National Pipe Taper — North America). Their thread angles and pitches differ, so a BSP male will not seal correctly in an NPT female even when the diameters look close — it binds, or it leaks under pressure weeks later. Within each standard, specify gender (male/external or female/internal) and form: tapered threads seal on the thread itself with tape or compound; parallel threads seal on a washer or O-ring and no amount of tape fixes a missing washer. A complete thread callout reads like "½" BSP female, parallel" — four facts, no ambiguity. On plastics, one more rule: plastic threads crack under metal-thread torque. Hand-tight plus a modest turn is the limit, and molded plastic-to-metal transition adapters beat cutting threads on plastic every time.

Transition Fittings: Where Two Systems Meet

Real buildings mix pipe systems — HDPE at the boundary, PPR or PEX inside, PVC for drainage — and every junction between systems needs a purpose-made transition fitting, almost always with a brass core. The common ones: a PPR-to-brass insert fitting (a brass thread molded into a PPR body) to connect valves, meters, and appliances; a PEX-to-thread adapter (crimp or expansion one side, BSP/NPT the other); a PVC male/female threaded adapter from solvent-weld to thread; and HDPE stub ends with backing flanges or transition couplings at the service entry. What never works: improvising — cementing unlike plastics, threading into unthreaded sockets, or relying on sealant to bridge a dimensional mismatch. The transition points are also where galvanic and grade rules bite: on potable systems the brass in every transition should be lead-free and dezincification-resistant, matching the valves — one under-spec adapter undermines an otherwise compliant system.

Joining Methods at a Glance

Across all systems there are really five ways a fitting grabs a pipe, and each has a personality. Solvent weld (PVC/CPVC): fast and cheap, chemically fuses into one piece — but it's permanent, needs cure time before pressure, and each material demands its own cement. Heat fusion (PPR, HDPE): the strongest joint of all, pipe and fitting become literally one polymer — at the price of a welder, power on site, and trained hands. Mechanical (PEX crimp/clamp/expansion, compression on copper and some plastics): no chemicals, no heat, instant pressure-readiness, demountable in some forms — but every joint depends on the ring, ferrule, or sleeve being the right part, correctly gauged. Threaded: universal for valves, meters, and equipment, demountable by design — but every thread is a potential leak path that lives on sealant quality and correct torque. Flanged: the serviceable joint for large diameters and pumps — bolted, gasketed, and rebuildable. A practical heuristic: permanent runs favour welded/fused joints; anything you'll ever service gets a union, flange, or mechanical joint on each side. The count of serviceable joints, not the total joint count, is what determines how maintainable the system is ten years in.

Special-Purpose Fittings Worth Knowing

Beyond the standard shapes, a handful of specialist fittings solve specific problems — and knowing they exist saves improvisation. A street elbow has one male and one female end, so it nests directly into another fitting where space is tight, saving a coupling and 40 mm of run. A sanitary tee and a wye + 45 both make a drainage branch, but they are not interchangeable: the sanitary tee suits vertical drops, while horizontal drain junctions want the wye's sweep — codes are specific about which goes where. A dielectric union separates dissimilar metals (copper to steel, for example) with an insulating ring so galvanic corrosion doesn't eat the joint; anywhere two metals meet in water, it's the difference between decades and years of service. Expansion offsets and loops — built from ordinary elbows — absorb the thermal growth of long hot runs so the stress never lands on a fitting socket. And tapping saddles clamp onto an existing main to add a branch without cutting the line, the standard way services join HDPE and PVC mains. None of these appears on a basic schedule until the day the drawing meets a real wall, a real main, or a real water heater — which is exactly when a complete catalog matters.

Metal Fittings Beyond Brass

Two other metal fitting families still matter in the wider "pipe fittings" world, even as plastics dominate new plumbing. Malleable and galvanized iron fittings — the classic banded elbows and tees — serve threaded steel pipe: gas lines, compressed air, legacy water systems, and structural uses like railings. On water duty they inherit steel's corrosion clock, which is why most water-side galvanized work today is replacement rather than new install. Stainless steel fittings (304/316) take over where corrosion, hygiene, or temperature rule out everything else: food and beverage lines, chemical duty, coastal exposure, and high-spec commercial plant. They cost several times a brass equivalent, so they appear where the duty demands them, not by default. For everyday potable plumbing, the practical metal remains lead-free DZR brass — at the valves, meters, and transitions — with iron and stainless reserved for their niches. The material logic is the same everywhere: match the fitting metal to the fluid, the pipe, and the corrosion environment, never just to the thread that happens to fit.

Sizing: the Four-Axis Match

A fitting fits when four axes line up. Size and convention: nominal (inch) and metric-OD systems coexist — a ½" nominal fitting and a 20 mm fitting are not the same part, so order pipe and fittings in one convention. Material system: as above — the fitting must belong to the pipe's family, in the right sub-family (CTS vs IPS in CPVC, PN class in PPR, SDR-matched electrofusion in HDPE). Pressure and temperature rating: the fitting must meet the line's rating at its working temperature; a Schedule 40 fitting on a Schedule 80 line caps the whole run. Standard: the fitting should carry the same product standard as the pipe (ASTM, EN, ISO as your market requires) plus the potable approval where it touches drinking water. Reducers deserve a note: step down through standard increments rather than jumping four sizes in one fitting, and on horizontal drainage prefer eccentric reducers that keep the pipe crown level so air doesn't pocket. When in doubt, the pipe's own maker lists exactly which fittings match — the safest spec is pipe and fittings from one catalog.

How to Build a Fitting Order That Assembles First Time

Walk the drawing line by line and count events, not guesses: every direction change (elbows — and whether 90° or 2×45°), every branch (tees/wyes, with reducing sizes noted), every size step (reducers), every serviceable component (unions or flanges either side), every system junction (transition adapters), every dead end (caps). Add the joining consumables to the same order — cement and primer per material, crimp rings and the go/no-go gauge, fusion sockets — because a site with fittings but the wrong glue is still stopped. Then add a sane spare margin: 5–10% on high-count small fittings (elbows, couplings), at least one spare of anything that would halt work if broken. The reason to order the whole kit from one manufacturer isn't convenience alone — it's that one catalog guarantees one sizing convention, one standard, and matched sub-families across pipe, fittings, valves, and transitions. That's how IFAN structures its product range across PPR, PVC/CPVC, PEX, HDPE, and brass: the elbow, the pipe it joins, and the valve downstream all come dimensionally matched, which is exactly what removes the "close but won't seal" class of callbacks.

Common Fitting Mistakes

Mixing material systems. A PVC fitting on CPVC, PEX fittings on the wrong grade, cement across unlike plastics — each looks close and fails. One pipe, one system.

Mixing thread standards. BSP into NPT binds or leaks. State standard, size, gender, and form on every threaded item.

DWV fittings on pressure lines. Drainage fittings aren't pressure-rated. Same shape name, different part.

Improvised transitions. Two systems meet only through a purpose-made (usually brass) transition fitting — never sealant and hope.

Forgetting the consumables. Fittings without the right cement, rings, or gauge stop the site just as surely as missing parts.

Frequently Asked Questions