A 1 1/2 in Schedule 40 PVC pipe measures 1.900 in outside diameter, 0.145 in minimum wall thickness, and 1.610 in inside diameter.
The “1 1/2 inch” label is a nominal size, not a measurement, so a fitting with that label may not thread onto the pipe. Every figure comes from one standard: the ASTM D1785 schedule tables.
Three measurements do the work: outside diameter, wall thickness, and inside diameter. One gets reported two ways depending on the chart.
Why Isn’t A 1 1/2 Inch PVC Pipe 1 1/2 Inches Wide?
Nominal pipe size is a naming system, not a measurement. Sizes trace back to iron pipe standards, and labels carried over when plastic replaced metal.
- Outside diameter (1.900 in). This matters at the fitting counter. Fittings, clamps, hangers, and repair couplings are sized to outside diameter and schedule, never the nominal label.
- Wall thickness (0.145 in minimum). Sets the inside diameter and pressure capacity. Since the table lists a minimum, production pipe can run slightly thicker.
- Inside diameter (1.610 in). The flow path. Pump charts, flow calculators, and drain sizing use it rather than the barrel label. Some tables list 1.590 in: a 1.610 in bore pairs with the 0.145 in minimum wall, 1.590 in with a thicker average wall. Both appear in manufacturer documents.
1 1/2 Inch PVC Pipe Dimensions: Where The Numbers Come From
ASTM D1785 defines Schedule 40 PVC dimensions, and every manufacturer’s chart traces back to it. Westlake Pipe lists 1 1/2 inch Schedule 40 pipe at 1.900 in OD, 0.145 in minimum wall, and 1.610 in ID.
That rating belongs to pressure-rated lines only; Schedule 40 PVC is also sold as DWV drain pipe and turf irrigation pipe, which carry different ratings and approved uses. A pressure figure from one submittal sheet does not transfer to another product at the same nominal size.
Expect small variation, not a different size class.
| Specification | Published Value | What It Controls |
|---|---|---|
| Nominal size | 1 1/2 in | A label for the sizing family, not a measurement |
| Outside diameter | 1.900 in | Fit of fittings, clamps, and hangers |
| Minimum wall thickness | 0.145 in | Pressure strength and inside diameter |
| Inside diameter | 1.610 in | Flow path and drain capacity |
| Alternate published ID | 1.590 in | Reflects average wall reporting |
| Schedule 80 OD / wall / ID | 1.900 / 0.200 / 1.500 in | Same outside, thicker wall, smaller bore |
| Pressure rating (one maker’s line) | 330 psi | Applies to that pressure-rated product only |
Does A 1 1/2 Inch Fitting Fit Every 1 1/2 Inch Pipe?
No. A fitting must match the pipe’s outside diameter and schedule, and a 1 1/2 inch label guarantees neither. Schedule 40 and Schedule 80 share the same 1.900 in OD, so pipe ends look interchangeable, but wall thickness, ID, and pressure rating all differ.
Retail listings are another trap. A page advertising a 1 1/2 inch ID while listing a 1.900 in OD and 0.145 in wall contradicts the standard table, usually because the seller copied the nominal size into the wrong field. Check the manufacturer’s submittal sheet, or measure the pipe, before trusting a shelf tag.
For pipe you plan to order instead of measure, this roundup of tested 1 1/2 inch PVC pipe picks compares brands on outside diameter, schedule, and pressure rating.
Run this check before you buy or glue:
- Read the schedule printed along the barrel, usually SCH 40 or SCH 80.
- Match fittings to the 1.900 in outside diameter and the same schedule.
- Size the flow path from the inside diameter, not the label.
- Confirm the pressure rating in the manufacturer’s document for that exact product line.
FAQs
Is the inside diameter always 1.610 inches on this size?
Not to the thousandth. The 1.610 in figure pairs with the standard 0.145 in minimum wall; some tables publish 1.590 in using an average wall. Manufacturing tolerances shift real measurements slightly, so treat 1.610 in as the table value.
Can Schedule 40 and Schedule 80 pipe of the same size share fittings?
Both share a 1.900 in outside diameter, so pipe ends can look interchangeable. Their walls and inside diameters differ, and Schedule 80 fittings are built for thicker pipe, so mixing schedules on a pressure system weakens the joint. Use fittings made for the schedule you bought.
Where is the size printed on a stick of PVC?
Manufacturers print the nominal size, schedule, and pressure rating along the barrel in repeating text, so a cut section still carries it. Look for something like 1-1/2 in SCH 40 PVC plus a pressure figure. That print is more reliable than a shelf tag or product listing.
References & Sources
- Westlake Pipe. “ASTM D1785/D2665 SCH. 40 PVC PRESSURE/DWV” Lists 1.900 in OD, 0.145 in minimum wall, 1.610 in ID, and a 330 psi rating for 1 1/2 in Schedule 40.
- Westlake Pipe. “ASTM D1785/D2665 PVC TURF IRRIGATION PIPE” Shows how pressure ratings and approved uses change across product lines.
- ASTM. “ASTM D1785-15e1 Standard Specification for PVC Plastic Pipe, Schedules 40, 80, and 120” Supports outside-diameter tolerance language by nominal size.
