Pipe Size & Material Reference
Overview
Quick-reference for selecting and identifying residential plumbing pipe by material + size. Sizing wrong undersizes the supply (low flow) or oversizes the drain (debris settles + smell). Material selection has code constraints (some materials banned for hot water, some banned outdoor, some banned in floor slabs).
Reference Table
Supply pipe (potable water):
| Material | Typical sizes | Pros | Cons | Code notes |
|---|---|---|---|---|
| Copper Type L | ½", ¾", 1", 1¼" | Durable 50+ years, soldered or pressed joints | Expensive, theft risk in vacant homes | Approved everywhere |
| PEX (cross-linked polyethylene) | ½", ¾", 1" | Easy install, freeze-tolerant, no scale | UV-degrades (cover outdoors), rodent-chewable | Approved most jurisdictions |
| CPVC | ½", ¾", 1" | Cheap, easy install | Brittle with age, sensitive to chemicals | Approved many jurisdictions |
| Galvanized steel | ½", ¾", 1" | Strong | Corrodes from inside; lifespan 40-60 years | Legacy only - new install banned most jurisdictions |
| Polybutylene | ½", ¾", 1" | (Was cheap install) | KNOWN failure mode; class-action settled | Banned - replace on sight |
Drain, waste, and vent (DWV):
| Material | Typical sizes | Pros | Cons | Code notes |
|---|---|---|---|---|
| PVC Schedule 40 | 1½", 2", 3", 4" | Most common residential DWV | Brittle at low temps; UV-sensitive | Standard residential DWV |
| ABS | 1½", 2", 3", 4" | Black PVC alternative | Code-specific; not universal | Some jurisdictions; verify locally |
| Cast iron | 2", 3", 4", 6" | Quiet, durable | Heavy, corrodes at threads | Renovation work; new install rare |
| Copper DWV | 1½", 2", 3" | Durable, formal aesthetic | Expensive | Rare in residential new construction |
Sizing rules of thumb
Supply branches for residential:
| Fixture | Cold supply | Hot supply |
|---|---|---|
| Lavatory sink | ½" | ½" |
| Kitchen sink | ½" | ½" |
| Toilet | ½" | - |
| Tub / shower | ½" | ½" |
| Washing machine | ½" | ½" |
| Dishwasher | ½" | - (hot inlet) |
| Hose bib | ¾" preferred | - |
| Main supply | ¾" or 1" | - (split sized appropriately) |
DWV branches:
| Fixture | Drain size | Vent size |
|---|---|---|
| Lavatory | 1½" | 1¼" |
| Kitchen sink | 1½" (2" preferred) | 1½" |
| Tub | 1½" (2" preferred) | 1½" |
| Shower | 2" | 1½" |
| Toilet | 3" | 2" |
| Floor drain | 2" - 3" | 1½" or 2" |
| Washer standpipe | 2" | 1½" |
| Main building drain | 3" or 4" | n/a |
Notes
- PEX color codes are NOT structural. Red = hot, blue = cold is convention only; either color works for either. Don't trust prior installer color discipline in walls.
- Polybutylene ("Poly-B") was installed 1978 - 1995. Looks like gray PEX but is its own failure category. Replace on sight; insurance often won't renew with poly-b in the home.
- Galvanized supply: when seen in a home, recommend a re-pipe quote. Lifespan estimate from the home's age - most galvanized installs from the 1950s - 1970s are at end-of-life now.
- Copper-to-other-metal joints need a dielectric union to prevent galvanic corrosion (especially copper-to-galvanized).
- Hot-water rating: CPVC up to 200°F; PEX-A up to 200°F; PEX-B up to 180°F; PVC NOT rated for hot water (use only for DWV or cold supply outdoors).
NEVER use PVC for supply hot water lines. PVC begins to soften around 140°F; a water heater discharging at 130°F + recovery cycles will gradually deform PVC joints and they'll leak. If you find PVC on hot supply in a home (often DIY installs), quote a re-pipe of the hot lines as urgent.
References
- IAPMO Uniform Plumbing Code, Chapter 6 (Water Supply) + Chapter 7 (Sanitary Drainage)
- Manufacturer datasheets (Uponor, Viega, Charlotte Pipe, Mueller)