HDPE Fittings Catalogue: The 8 Fields to Check Before You Compare Quotes

ISO 4427-3 sets out eight pieces of information that must appear on a polyethylene fitting for water supply. Six apply to every fitting — standard number, manufacturer's identification, traceability data, nominal diameter with the pipe series, material designation, and pressure rating in bar. Two more apply conditionally: a tolerance grade on large spigot fittings, and an SDR fusion range on electrofusion fittings. That list is not a recommendation from a purchasing blog. It is Table 8 of the standard, and it is the closest thing the industry has to a definition of a complete catalogue line.

Most HDPE fitting catalogues you will be sent do not present their data that way. They present a photograph, a part number, a size column, and a price. Which is fine, until three suppliers send you three documents built on three different conventions and you have to decide which quote is actually cheapest. At that point the catalogue stops being marketing material and becomes the instrument you are comparing with — and if it is missing fields, you are comparing guesses.

What a Catalogue Has to Tell You Before You Can Compare Anything

Here is the situation that sends buyers looking for this page. You have asked three suppliers for HDPE fittings on the same bill of quantities. Supplier A's catalogue lists a 110 mm tee as "PE100 SDR11 PN16". Supplier B lists what looks like the same part as "dn 110 / S 5, PE100". Supplier C lists "4 IPS DR11 PE4710". Three documents, three conventions, and a price spread wide enough that somebody is either very competitive or selling you something else.

Two of those three lines describe the same geometry. The third is on a different sizing system entirely and is not a 110 mm part at all. Nothing in any of the three catalogues tells you which is which, because each was written for a buyer who already knew the convention it uses.

This is the part worth being blunt about: until the goods arrive, the document is the product. Everything you are buying exists to you as a line in a PDF, and the quality of your decision is capped by the completeness of that line. A missing field is not a formatting problem. It is a specification you have silently agreed to let the supplier choose on your behalf, and you will find out which one he chose when the container is discharged.

What makes two lines comparable

Two catalogue lines are comparable when they agree on five things: the sizing axis, the material grade, the wall-thickness series, the pressure rating, and how the fitting was made. Miss any one and the comparison is arithmetic performed on different units. The rest of this page walks the fields in the order a buyer actually needs them, starting with the list the standard itself imposes.

The Eight Fields ISO 4427-3 Requires on a Fitting

ISO 4427-3 is the international standard for polyethylene fittings used to convey water for human consumption, raw water before treatment, and water for general purposes. Its current edition is the second, ISO 4427-3:2019, published in August 2019, which cancels and replaces the 2007 first edition. It applies to fittings rated to a maximum operating pressure of 25 bar with 20 °C as the reference temperature, and it explicitly covers electrofusion, butt fusion and socket fusion fittings, fabricated fittings, mechanical fittings and flanged fittings.

Its marking clause is the useful part for a buyer. The standard sets a minimum required marking in a table of aspects — clause 11.2 and Table 8 in the 2007 edition, carried into clause 12.2 of the 2019 edition. These are the fields a conforming fitting must carry on the part itself, which makes them the natural minimum for the catalogue line that sells it.

Aspect	What it looks like	What it settles for you
Standard number	ISO 4427	Which rulebook the part claims to meet — and which test requirements follow from that
Manufacturer's identification	Name or code	Who is accountable when a joint fails on site
Manufacturer's information	Figures or code giving traceability to production period within year and month, plus the production site where there is more than one	Whether a defect can be traced to a batch, or only to a company
Nominal diameter and pipe/SDR series	dn 110/S 5, or dn 110/SDR 11	The geometry — diameter and wall thickness together, not diameter alone
Material and designation	PE 80, PE 100	The resin classification the pressure rating was calculated from
Pressure rating in bar	PN 12,5	The rating of the fitting — which is not automatically the rating of the pipe it mates to
Tolerance grade (spigot fittings, dn ≥ 280 mm)	Grade A	How tightly the spigot end is controlled on large diameters
SDR fusion range (electrofusion only)	SDR 11–SDR 26	Which pipe wall thicknesses the coupler will actually fuse to

Read the third row again, because it is the one buyers skip and claims departments care about. The standard does not ask for a vague batch reference; it asks for traceability to the production period within year and month, and to the production site where the manufacturer runs more than one. Twelve months later, with a failed section of main and a supplier who would rather discuss anything else, that field is the difference between a batch investigation and an argument.

Mechanical fittings sit inside ISO 4427-3's scope alongside fused types, and the marking rules apply to them too.

The marking rules behind the fields

The standard also governs how the marking is applied, and these clauses are quietly useful at inspection. Marking must be permanent and legible, applied so that it does not initiate cracks or other failure. Where printing is used, the colour of the printed information must differ from the base colour of the product. The marking must be legible without magnification. And there must be no marking over the minimum spigot length of the fitting — the zone that gets scraped and fused.

That last rule gives you a cheap incoming-inspection test that needs no equipment. If ink sits on the spigot where the coupler has to grip, the part was not marked to the standard it claims. The standard is also realistic about what happens afterwards: it notes that the manufacturer is not responsible for marking rendered illegible by painting, scratching, covering or detergents during installation and use. So the marking you are entitled to judge is the marking on arrival, which is an argument for photographing it at container discharge rather than at first complaint.

Reading the Size and Pressure Line: dn, SDR, S, PN

Return to Supplier B's line, "dn 110 / S 5". A buyer used to SDR notation reads that as an unknown and asks the supplier what it converts to. He does not have to. ISO 4065, the universal wall thickness table for thermoplastics pipes, defines the pipe series S as a dimensionless number related to nominal outside diameter and nominal wall thickness, given by S = (SDR − 1)/2. The current edition is the third, ISO 4065:2018, which replaced the 1996 second edition.

Run it: S 5 gives SDR = 2 × 5 + 1 = 11. Supplier B's "dn 110 / S 5" and Supplier A's "SDR11" are the same geometry. You just resolved a specification question without an email, and — more to the point — you now know that the two quotes are comparable on that axis, which is not something either catalogue told you.

Notation on the line	What it is	Relationship
dn	Nominal outside diameter in millimetres	The metric sizing axis; independent of wall thickness
SDR	Standard dimension ratio	SDR = 2S + 1
S	Pipe series	S = (SDR − 1)/2, and also S = σs/PN
en	Nominal wall thickness	en = dn/(2S + 1)
PN	Nominal pressure in bar	Follows from S and the design stress of the grade

Same outside diameter, three wall series: a lower SDR means a thicker wall and a higher pressure rating at the same nominal size.

The second identity in that table is the one worth internalising. ISO 4065 defines S as the quotient of the design stress and the maximum allowable operating pressure: S = σ_s/PN. This is why the same SDR gives different pressure ratings on different grades — the geometry is fixed, the design stress is not.

A PE100 fitting and a PE80 fitting at identical SDR are not equivalent parts, and a catalogue that prints SDR without printing the grade has told you half a specification. Our PE100 versus PE80 comparison covers what that difference is worth in practice, and the HDPE pipe sizes guide carries the full SDR-to-pressure chart if you need to look up a specific pairing.

Two sizing systems that do not convert

Supplier C's "4 IPS DR11 PE4710" is the trap. That line is written on the North American axis, where ASTM F714 specifies PE pipe by outside diameter in the DIPS, IPS and metric systems, and dimension ratio is written DR rather than SDR. An IPS 4-inch pipe has an outside diameter of 114.3 mm, not 110 mm. The two systems are not interchangeable and no arithmetic converts a part between them — a metric fitting will not fuse to an IPS pipe.

If your project is specified in metric dn and one quote comes back in IPS, that supplier has not offered you a cheaper version of the same thing. He has offered you a different thing, and if it is fused into a metric network the joint is the failure. Ask which axis the quote is on before you compare a single price. You can see how a metric range is normally published — grades, SDR series and pressure classes stated together — on our HDPE pipe and fittings range.

The Field Most Catalogues Bury: Moulded or Fabricated

This is where the money usually is, and it is the field most likely to be absent from the line you are reading.

A moulded fitting is injection-moulded as one piece, with wall thickness engineered at the junction where stress concentrates. A fabricated fitting is built from lengths of pipe, cut and butt-fused together. Both are legitimate, both are inside ISO 4427-3's scope, and for large diameters fabrication is often the only economic option. But they do not carry the same pressure, and the standard is explicit about it.

ISO 4427-3 Annex B, which is normative, states that the PN rating of fabricated fittings "shall be derived from the PN of the used pipes and the geometry derating factors given in B.3 and B.5". In other words, the pressure rating of a fabricated fitting is a calculated number, not an inherited one. The pipe it was cut from does not confer its rating on the fitting.

The mitred seams and the unreinforced junction on the right are the reason the standard applies a derating factor.

The factors, and what they do to a price comparison

For tees fabricated from pipe segments, Annex B.5 gives the rule as PN = f_T × PN_pipe, where f_T has a value of 0,5. Half. A segmented tee fabricated from PN16 pipe is a PN8 fitting.

For segmented bends, Annex B.3 gives PN = f_B × PN_pipe, with the factor set by the cut angle of the segments, and the cut angle capped at 15°.

Fabricated item	Derating factor	From PN16 pipe, the fitting is
Segmented tee	fT = 0,5	PN8
Segmented bend, cut angle ≤ 7,5°	fB = 1,0	PN16
Segmented bend, 7,5° < cut angle ≤ 15°	fB = 0,8	PN12,8
Swept bend formed from pipe	Usually none	PN16

Note the bottom two rows, because they stop this from being a story about fabricated fittings being inferior. A segmented bend cut at a shallow enough angle carries the full pipe rating, and a swept bend formed from pipe rather than assembled from segments usually carries no derating at all — Annex B.4 says so directly, subject to the testing in Table B.1. The variable is geometry, not the word "fabricated".

Now put it back into the quote comparison. Supplier A quotes a moulded PN16 tee. Supplier B quotes a fabricated tee, describes it as "PN16 pipe construction", and is thirty percent cheaper. If B's tee is segmented, the standard rates it PN8, and you are not looking at a discount — you are looking at a part with half the pressure rating of the one you asked for, in a line item where the branch is the most highly stressed point in the assembly. The thirty percent is real. So is the fact that it is a different product.

What to ask for, and why the supplier already has it

You do not have to take this on trust, and the request is not an imposition. Annex B.1 requires that "the pressure rating as well as the applicable derating factor, f, shall be recorded in the manufacturer's technical file", and makes the manufacturer responsible for demonstrating conformity to the declared PN. A supplier building to the standard has already written the number down. Asking for it costs him a document retrieval, not a test programme.

The same annex tells you what a real test report should show. The hydrostatic requirement for fabricated fittings applies the derating factor to the test stress itself: for PE 100, 12,4 MPa × f at 20 °C over 100 hours, and 5 MPa × f at 80 °C over 1 000 hours, on three test pieces. If a report quotes a stress with no f applied to it, either the fitting was not derated or the report is not the one the standard asks for.

One further caution from the same clause: where fabricated fittings are made from pipe of the next lower SDR and machined back, the factors may differ from the annex values. Ask what the declared factor is rather than assuming 0,5.

Which Standard the Catalogue Is Written Against, and Which Edition

A standard number on a catalogue cover is a claim about which rulebook the product was built to. An edition year is a claim about whether that rulebook is still current. Buyers check the first and almost never check the second, which is how a certificate quoting a withdrawn document passes through procurement unchallenged.

The European standard for PE fittings has moved. EN 12201-3:2011+A1:2012 has been superseded by EN 12201-3:2024, published at the end of December 2024 with a corrigendum incorporated the same month, and the British adoption of the older edition is listed as withdrawn. If a supplier's certificate cites the 2011 edition today, that is not automatically a bad product — but it is a document worth a question, because it tells you when his conformity paperwork was last refreshed.

Standard	Current edition	What it covers
ISO 4427-3	2019 (second edition)	PE fittings for water supply and pressure sewerage, international
EN 12201-3	2024, superseding 2011+A1:2012	PE fittings, European; scopes electrofusion socket and saddle, spigot end, socket fusion, mechanical and fabricated fittings
ASTM D3261	D3261-24	Butt heat fusion PE fittings; includes materials, dimensions, marking, sustained pressure and burst
ASTM F714	F714-25	PE pipe sized on outside diameter (DR-PR), DIPS, IPS and metric 90 mm and larger
ASTM F1055	Cited for electrofusion	The manufacturing standard US specifications name for electrofusion fittings

Two practical rules follow. First, match the standard to the destination market's approval regime rather than to whichever standard the supplier prefers to quote — a catalogue built on ASTM is the right document for a North American project and the wrong one for a metric tender that will be inspected against ISO or EN. Second, if a catalogue cites both ISO and ASTM on the same page, check that individual lines are not mixing axes, because a document can be honest at the cover and confused at the row.

And where your project needs drinking-water approval on top of the product standard, that is a separate certificate with its own scope and expiry. Our guide to HDPE pipe standards and certification covers how to verify one.

Turning a Catalogue Into a Quote You Can Actually Compare

Take the three lines from the top of this page and normalise them properly. This is the whole method in one worked example, and it takes about ten minutes per bill of quantities once you have done it twice.

One line item, three quotes: the comparison only means something once the five fields agree.

Scoring the three quotes

Supplier A — "110 mm tee, PE100 SDR11 PN16, moulded". Complete. Metric axis, grade stated, wall series stated, pressure stated, method stated. This line can be compared.

Supplier B — "dn 110 / S 5, PE100 tee". S 5 converts to SDR11, so the geometry matches A. Grade matches. But no pressure class is printed and no manufacturing method is stated. Two fields missing, and they are the two that decide whether this is the same product. If it turns out to be segmented, the tee is rated at half the pipe's PN, and B's price advantage is explained.

Supplier C — "4 IPS DR11 PE4710". Different sizing axis. IPS 4 inch is 114.3 mm outside diameter, not 110 mm. This is not a competing quote for the same part; it is a quote for a different part that cannot be fused into a metric network. Exclude it, or re-tender it against the metric spec.

The outcome is not that A wins. It is that only A can be scored, that B has to answer two questions before its price means anything, and that C was never in the comparison. Most of the value here is in disqualifying false comparisons before they reach a spreadsheet — a cheap quote that turns out to be a different specification does not save money, it moves the cost to the part of the project where it is most expensive to discover.

The fields to require in writing

Send this list back as the required format for every quoted line and the comparison problem largely disappears:

• Sizing axis and diameter — dn in millimetres or IPS/DIPS in inches, stated explicitly, never just "4 inch" or "110".
• Wall series — SDR or S. If they give one, you can derive the other.
• Material designation — PE 80, PE 100 or the ASTM cell classification, because SDR without grade is half a spec.
• Pressure rating of the fitting — in bar, for the fitting itself, not the pipe it mates to.
• Manufacturing method — moulded, fabricated/segmented, or electrofusion, plus the declared derating factor f where fabricated.
• SDR fusion range — for every electrofusion item, since a coupler only fuses to the wall thicknesses it was designed for.
• Standard and edition — "EN 12201-3" is incomplete; "EN 12201-3:2024" is a claim you can check.
• Marking specification for fabricated items — since the standard leaves it to agreement, agree it here rather than discovering it at discharge.

The commercial fields a catalogue will not carry

Four things decide whether an order actually happens, and none of them belongs to the product standard, so no catalogue will answer them. Ask them in the same email.

• Minimum order. For pipe systems this is structured rather than a single number, and it varies by supplier and by how many moulds a size mix has to run through. The structure matters more than the figure: ask whether the minimum is per line item or per container, whether mixed sizes count toward it, and whether mixed materials — buried PE main, indoor risers, brass valves — can share the load. A single-material supplier says no, and that answer moves your landed cost more than his unit price does.
• Price basis. Polyethylene fitting prices track resin, and quotes move. What matters more than the number is what drives it and how long it holds: which grade, which SDR, moulded or fabricated, what quantity break, and the validity period of the quotation. A price with no stated validity is not a price, it is an indication.
• Lead time. Ask for production and shipping separately, and ask what changes each — a size mix that spans many moulds behaves differently from a single high-volume size. Our HDPE pipe pricing guide goes into what moves the landed number.
• Sampling and verification. Before a first container, ask for samples of the specific items you are unsure about, and for the test reports that match them — for fabricated items, the Annex B hydrostatic report with the derating factor applied. Agree what happens if incoming inspection finds marking that does not match the agreed specification, because that clause is easy to write before the order and impossible after.

The specification you never wrote down is the one you will argue about, at the worst possible moment: container discharged, fittings on site, crew started. The supplier's position will be that he shipped what was ordered, and he will usually be right — the order was silent. Ten minutes spent making three quotes comparable is the cheapest risk transfer available on a pipe purchase, and all of it happens before you commit a cent.

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