HDPE Pipe Sizes

One Nominal, Two Pipes

Borrowing two series means the same number names two different pipes, and the gap grows with size. Both are sold as that nominal, both are correct, and they will not fuse to each other.

At 48 inch the two are 71.1 mm apart. Butt fusion needs the diameters to match, so this is not a tolerance question — it is two products that cannot be joined, ordered under one name.

SDR Is a Definition, Which Makes It Checkable

DR, or SDR, is the dimension ratio: outside diameter divided by minimum wall. It is a definition rather than a table lookup, which makes it an exact per-cell check — and also means a table produced by dividing passes it while being wrong about what the standard publishes. See rejected_sources.. The wall is the diameter divided by the dimension ratio, by definition rather than by convention, and that is unusual — nothing else on this site has an identity that exact to check against. A crossed column cannot survive it, and neither can a dropped row.

It does stop holding at the small end, where a handling minimum takes over from the ratio. These are the rows where the printed ratio is furthest from the pipe’s actual one:

The direction matters. A pipe thicker than its ratio is a pipe with more material than the label promised; the reverse would be a defect. Everything found here runs the safe way.

The Diameter Series

IPS

DIPS

ISO

398 of 682 rows verified against DR, or SDR, is the dimension ratio: outside diameter divided by minimum wall. It is a definition rather than a table lookup, which makes it an exact per-cell check — and also means a table produced by dividing passes it while being wrong about what the standard publishes. See rejected_sources. and against the borrowed diameter series; 260 carry a single-source label and 21 could not be confirmed. How this data was verified.

A Gate That Clean Has Its Own Trap

An exact identity is the best check available and it invites the worst kind of source. A publisher who simply calculates the diameter over the ratio for every cell produces a table that passes the check perfectly — and is wrong about the standard, which rounds onto a wall series and imposes a handling minimum at the small sizes.

One source in this corpus was rejected for exactly that: every cell exactly the division to two decimals, no rounding onto the wall series, no minimum-wall floor, and a 20 mm pipe given a 0.61 mm wall that nobody makes. A calculator wearing a standard’s name. It is the clearest reminder we have that passing arithmetic and being right are different claims.

The ratio also caught something no other check could: one publisher’s table has lost a row, so the diameters are right and the walls are shifted up a size. Bore and mass reconcile with each other, a diameter check passes, and only the ratio exposes it. That same publisher’s data had already been rejected once on this project for the same fault, and a fresh fetch found it again. It is listed with the rest at errors found in published pipe data.

What We Could Not Verify

AS/NZS 4130 (Australian PE)

zenith_1477.html and iplex_guide.html are both AS/NZS 1477, which is PVC-U, not PE. The filenames read like PE sources and their PN tables would slot straight into this dataset. They are a different material and they are not here.

wplaw_sdr.pdf

The name says SDR, so it reads like a PE document. It is a Cresline PVC1120 ASTM D2241 catalogue. It belongs to data/pvc.json, not here.

ISO 4427 via engineeringtoolbox

ent_iso4427.html publishes inside diameters against PN classes without naming the PE grade. Without the grade a PN cannot be tied to an SDR, so the dimension ratio would have to be invented from the numbers and then used to check them. Circular; not compiled.

engcosuite.com ISO 4427 chart

engco_iso4427.html: 100% of its cells are exactly OD/DR to 2 dp, with no rounding onto the ISO wall series and no minimum-wall floor — including dn 20 at SDR 33, a 0.61 mm wall nobody extrudes. Presented as an ISO 4427 chart; it is a division. Not compiled.

CTS and SIDR polyethylene

Copper Tube Size and Standard Inside Diameter Ratio PE are two further series. No source in this set carries a full CTS or SIDR wall table, and SIDR is sized on the BORE, so e = OD/DR cannot gate it at all. Not compiled.

PE 80 / PE 63 / PE 4710 pressure classes

Only the geometry is compiled. A pressure class depends on the resin's minimum required strength, the design factor and the service temperature, none of which is a dimension, and the sources already disagree about them: 317 against 318 psi at DR 7.3, and 63 against 64 psi at DR 32.5. Nothing here can adjudicate that.

Wavin gas (EN 1555-2) and sewer tables

Wavin's manual carries two further tables at the same diameters. Not compiled: they add pressure classes rather than geometry, and the water table already supplies every wall in them.

dn 450 at SDR 26, 21, 13.6 and 9

Rifeng is the only bloc that carries those four cells and its dn 450 line has lost a decimal point in the source's text layer. The row was refused rather than realigned. See findings.cells_lost_to_malformed_source.

Pressure classes are deliberately absent. The sources disagree with each other about them, nothing here can settle which is right, and a pressure rating is the one figure on a plastic pipe where being confidently wrong has consequences.

HDPE Against the Other Materials

HDPE and PVC pipe sizes are the two plastics that ride the steel diameters, and they do it differently: PVC takes the steel series and the schedule names with it, while HDPE takes the series and replaces the schedule with a ratio. For the material HDPE borrows its other series from, see ductile iron pipe sizes, and for the drainage material that shares none of them, cast iron pipe sizes.

Frequently Asked Questions

What is the outside diameter of 4-inch HDPE pipe?

That question has two answers and you have to say which series. In IPS it is 4.500 in, the same as 4-inch steel pipe. In DIPS it is 4.800 in, the same as 4-inch ductile iron. The two are 7.62 mm apart and will not join to each other.

Does HDPE have outside diameters of its own?

No, and that is the most useful thing to know about it. IPS matches the ASME B36.10M steel series at all 28 sizes checked, to the last digit; DIPS matches the AWWA ductile iron series at all 14. HDPE borrows whichever series the pipework it is replacing already used.

What does SDR mean on HDPE pipe?

Standard dimension ratio: the outside diameter divided by the wall thickness. A DR 11 pipe has a wall one eleventh of its diameter, whatever its size — which is why the ratio, not the wall, is what gets specified. It is a definition rather than a measured property, so it can be checked exactly, and we check every row against it.

Is the wall always the diameter divided by the SDR?

Almost, and the exceptions are worth knowing. At the small end the ratio stops holding because a minimum wall takes over for handling: the worst case here is IPS 0.5 printed as DR 32.5, whose actual ratio is 13.6. Every departure runs the same way — the pipe is thicker than its label demands, never thinner.

Can IPS and DIPS HDPE be joined together?

Not by fusion. Butt fusion needs matching outside diameters and these differ by 7.62 mm at the smallest colliding size and 71.1 mm at 48 inch. Both are sold as that nominal size, so the mistake is made on paper long before anything reaches the site.