Copper Pipe vs. Nominal Pipe Sizes & Schedules
Comparing 2 standards across 13 specifications. 13 key differences identified.
Seamless copper water tubing is standardized under ASTM B88 into three primary wall thickness grades: Type K (Green / Heavy Wall for underground mains), Type L (Blue / Medium Wall for standard interior residential plumbing), and Type M (Red / Thin Wall for low-pressure hydronic heating). All three types share identical outer diameters for standard solder, flare, and press fittings.
Nominal Pipe Size (NPS) and Schedule designations under ASME B36.10M standardize the outer diameter, wall thickness, and pressure capabilities of forged steel, wrought iron, and stainless pipe. For NPS 1/8 to NPS 12, the nominal number represents approximate inside diameter, while maintaining a standardized fixed outer diameter across Schedule 40 (Standard) and Schedule 80 (Extra Strong) walls.
Specification Comparison Table
13 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Standard
|
ASTM B88 / NSF 61 | ASME B36.10M / ASTM A53 / ASTM A106 |
|
Type K (Green Stripe)
|
Heavy wall: 1/2" = 0.049" (1.24 mm) | 3/4" = 0.065" (1.65 mm) wall | — |
|
Type L (Blue Stripe)
|
Medium wall: 1/2" = 0.040" (1.02 mm) | 3/4" = 0.045" (1.14 mm) wall | — |
|
Type M (Red Stripe)
|
Thin wall: 1/2" = 0.028" (0.71 mm) | 3/4" = 0.032" (0.81 mm) wall | — |
|
Outer Diameter Formula (CTS)
|
Actual OD = Nominal Size + 1/8 inch (0.125") | — |
|
Joining Methods
|
Capillary solder (sweat), ProPress copper crimp, flare, compression | — |
|
Operating Temperature
|
Up to 400°F (204°C) continuous in hydronic heating | — |
|
Metric Equivalent
|
— | DN (Diamètre Nominal) in millimeters (e.g., NPS 1/2 = DN 15) |
|
NPS 1/2" Dimensions
|
— | OD: 0.840" (21.3 mm) | Sch 40 Wall: 0.109" (2.77 mm) | Sch 80 Wall: 0.147" (3.73 mm) |
|
NPS 3/4" Dimensions
|
— | OD: 1.050" (26.7 mm) | Sch 40 Wall: 0.113" (2.87 mm) | Sch 80 Wall: 0.154" (3.91 mm) |
|
NPS 1" Dimensions
|
— | OD: 1.315" (33.4 mm) | Sch 40 Wall: 0.133" (3.38 mm) | Sch 80 Wall: 0.179" (4.55 mm) |
|
NPS 2" Dimensions
|
— | OD: 2.375" (60.3 mm) | Sch 40 Wall: 0.154" (3.91 mm) | Sch 80 Wall: 0.218" (5.54 mm) |
|
Schedule Transition Boundary
|
— | For NPS ≥ 14, Nominal Pipe Size equals the exact Outer Diameter in inches |