PVC & CPVC Pipe Dimensions and Specifications

Plastic pipe is specified by nominal size, not by any dimension you can measure on it. A 2" PVC pipe has an outside diameter of 2.375", an inside diameter that changes with the schedule, and no dimension anywhere equal to 2". This page gives the real numbers — outside diameter, wall thickness, inside diameter and pressure rating — for PVC and CPVC in the schedules and standards we stock.

How plastic pipe is sized

PVC and CPVC schedule pipe use IPS (Iron Pipe Size) dimensions, inherited from steel pipe. Two consequences follow, and both catch people out:

• Outside diameter is fixed by nominal size and never changes with schedule. A 2" Schedule 40 and a 2" Schedule 80 pipe have the identical 2.375" OD. That is why the same socket fitting accepts both.
• Schedule changes the wall, so it changes the bore. Going from Sch 40 to Sch 80 buys pressure rating and costs flow area. On 2" pipe the ID drops from 2.067" to 1.939" — about 12% of cross-sectional area gone.

CPVC is sold two ways, and they are not interchangeable. CPVC Schedule 80 uses IPS dimensions like PVC. CPVC CTS (the cream-colored hot and cold water tubing) uses copper tube size — OD is nominal plus 1/8". A 1/2" CTS fitting will not fit 1/2" IPS pipe.

PVC Schedule 40 — dimensions and pressure (ASTM D1785)

Pressure ratings are for PVC 1120 at 73°F, water, non-shock. Note that 2-1/2" is rated higher than 2" — it is not a typo. The wall jumps disproportionately at that size, so the pressure rating goes up before resuming its decline.

PVC Schedule 80 — dimensions and pressure (ASTM D1785)

Where the pressure rating comes from

You do not have to take the tables on faith. Every rating above is the ISO thin-wall formula applied to the hydrostatic design stress for PVC:

P = 2S ÷ (SDR − 1)   where  SDR = OD ÷ wall

S is the hydrostatic design stress: 2,000 psi for PVC 1120 and CPVC 4120 at 73°F (a 4,000 psi design basis with a 2:1 safety factor).

Worked on 1" Schedule 40: SDR = 1.315 ÷ 0.133 = 9.89. P = (2 × 2000) ÷ (9.89 − 1) = 4000 ÷ 8.89 = 450 psi. That is exactly the table value, and the same arithmetic reproduces every row on this page.

The practical use: if you are handed a pipe with a wall thickness that matches no schedule — SDR 21, SDR 26, class pipe — you can rate it yourself from the same formula.

Temperature derating — the number most people skip

Every pressure rating above is at 73°F. PVC loses strength quickly as it warms, and the derating is severe enough that it decides whether the material is usable at all. Multiply the 73°F rating by the factor:

Schedule 40 or Schedule 80?

Two rules that decide most jobs. Threaded plastic connections lose half the rating — cutting threads removes wall and creates a stress riser, so a threaded Schedule 80 joint is rated at 50% of the solvent-welded value. Where you can solvent weld, solvent weld. And Schedule 40 is not a threading material at all; if the design needs threads, it needs Schedule 80.

PVC DWV (ASTM D2665)

DWV pipe carries drain, waste and vent — gravity flow, no pressure. It is made to Schedule 40 dimensions, so a DWV pipe and a Schedule 40 pressure pipe of the same nominal size share OD, wall and ID, and take the same socket dimension.

What differs is what it is certified for. DWV pipe and fittings carry no pressure rating and must never be used on a pressure line, and DWV fittings have drainage-pattern geometry — long-sweep bends, directional tees, a slight internal slope at the socket — designed to keep solids moving. That geometry is also why you cannot substitute a pressure fitting into a drain: a sanitary tee and a pressure tee are not the same part.

Cellular core PVC (ASTM F891) is a DWV pipe with a foamed core between two solid skins. Same OD, lighter, cheaper, and accepted for DWV by most codes — but confirm your jurisdiction before specifying it, and never use it under pressure.

Sewer and drain pipe is a different product

Sewer and drain pipe (ASTM D2729, and SDR 35 to ASTM D3034) looks like DWV and is not. It is thinner walled, it is for gravity service outside the building, and it is generally not permitted for drain, waste and vent inside a structure. The OD is also different on D2729 pipe, so DWV fittings do not fit it — the two systems need their own fittings, and joining them takes a purpose-made adapter.

CPVC CTS — hot and cold water (ASTM D2846)

The cream or tan tubing used for potable water distribution. Sized to copper tube size, SDR 11, sizes 1/2" through 2". It uses copper tube dimensions, so it drops into a system laid out for copper.

CPVC CTS to D2846 is rated 400 psi at 73°F and 100 psi at 180°F — the 180°F figure is the one that matters, because that is the number that qualifies it for domestic hot water.

CPVC Schedule 80 (ASTM F441)

CPVC Schedule 80 uses the same IPS dimensions and the same 73°F pressure ratings as PVC Schedule 80 — both materials have a 2,000 psi design stress at that temperature, so the Schedule 80 table above applies unchanged.

The difference is entirely thermal. PVC stops at 140°F. CPVC is rated to 200°F, which is why it is the material for hot water distribution, hot process lines and applications a PVC system cannot survive. CPVC has its own derating curve, steeper than PVC’s past 140°F — take those factors from the pipe manufacturer’s published table for the exact product.

Solvent cement — match the cement to the material

Solvent welding is a chemical fusion, not gluing. The cement softens both surfaces and they weld into one piece as the solvent leaves. Which means the cement has to be formulated for the specific resin.

• Never use PVC cement on CPVC. D2564 does not soften CPVC properly. The joint will look right and fail under heat and pressure — which is exactly when it is worst.
• Do not solvent weld ABS to PVC. Transition cement exists, but many jurisdictions prohibit the joint outright and require a mechanical shielded coupling instead. Check the local code before you commit.
• Match cement body to pipe size. Regular body for small diameters, medium and heavy body as size grows — a thin cement on 4" pipe will not bridge the gap in the socket.
• Temperature governs cure, not set. Below 40°F use a cold-weather formulation. Set and cure times on the can are minimums that assume the stated temperature; cold, humid or large-diameter work needs longer before a pressure test.

Standards referenced

• ASTM D1785 — PVC pipe, Schedules 40, 80 and 120.
• ASTM D2665 — PVC drain, waste and vent pipe and fittings.
• ASTM D2466 / D2467 — PVC socket fittings, Schedule 40 and Schedule 80.
• ASTM D2464 — PVC threaded fittings, Schedule 80.
• ASTM F891 — PVC cellular core pipe.
• ASTM D2729 / D3034 — PVC sewer pipe and SDR 35 sewer pipe.
• ASTM F441 — CPVC pipe, Schedules 40 and 80.
• ASTM F438 / F439 — CPVC socket fittings, Schedule 40 and Schedule 80.
• ASTM D2846 — CPVC hot and cold water distribution system, CTS.
• ASTM D2564 / F493 / D2235 / F656 — solvent cements for PVC, CPVC and ABS, and PVC primer.
• NSF/ANSI 61 — drinking water system components. Look for the NSF-pw mark on any pipe carrying potable water.

Shop PVC and CPVC

• PVC pipe and CPVC pipe
• PVC Schedule 40 fittings
• PVC Schedule 80 fittings
• PVC DWV fittings
• CPVC fittings
• Sewer & drain pipe and sewer & drain fittings
• ABS pipe and ABS DWV fittings
• Solvent cements and primers

Need a submittal or a sizing check on something we stock? Call +1 (623) 307-5144 or email info@thehousesupplier.com.