Recycled Content in Plastic Pipe: What ISO Actually Permits

The Question Behind the Question

When a buyer asks a Chinese pipe supplier “is there recycled material in this pipe?”, the supplier hears a yes/no question and answers “100% virgin”. The buyer rarely believes it, and the conversation stops. The real question is more precise and far more answerable: what category of material is in the wall, where did it come from, and what document can you show me? The standards do not treat “recycled” as one thing — they define three material categories, permit one, and forbid the others outright, and the boundary has nothing to do with whether the pipe is made in China, Germany or Turkey.

ISO Splits Material Into Three Categories, Not Two

Most procurement conversations run on a two-box model: virgin, or recycled. The standards use three, and the middle one is where the confusion lives.

ISO 15494:2015 clause 3.2.2 defines virgin material as “material in a form such as granules or powder that has not been subjected to use or processing other than that required for its manufacture and to which no reprocessable or recyclable materials have been added”. Note the final clause: “virgin” is defined by the absence of any added reprocessable or recyclable material. So a supplier cannot claim both “100% virgin resin” and “we add a little regrind” — those contradict each other at the level of the definition.

The second box, own reprocessable material, is defined narrowly at clause 3.2.3: “material prepared from clean rejected unused pipes, fittings, or valves, including trimmings from the production of pipes, fittings, or valves, that will be reprocessed in a manufacturer’s plant after having been previously processed by the same manufacturer”. ISO 21138-1:2007 clause 3.1.3.2 adds that the formulation must be “known”. Every qualifier does work — clean, unused, trimmings, same manufacturer, known formulation. Floor sweepings, pipe returned from a job site and regrind bought from a trader all fail the test, however clean the bag looks.

The third box is external reprocessable material — and the clarifying fact is where it appears. ISO 21138-1:2007 defines all three categories, at clauses 3.1.3.1, 3.1.3.2 and 3.1.3.3, and it governs non-pressure buried drainage and sewerage. The pressure-pipe standards contain no such category at all.

The split is by application, not by polymer: the same polypropylene that may legitimately carry recyclate into a buried stormwater pipe may not carry it into a pressurised hot-water riser. That resolves the contradiction buyers meet when they read that the industry is expanding recycled content, then hear a plumbing supplier insist recyclate is banned. Both are true, about different products.

The Permission Clause, Read Verbatim

ISO 15494:2015 clause 5.4 states the operative rule: “The use of own reprocessable material obtained during the production and testing of components according to this International Standard is permitted in addition to virgin material, with the exception of PE-X. Reprocessable material obtained from external sources and recyclable material shall not be used.”

In-house rework is permitted, not tolerated as a grey area — buyers who treat any regrind as automatic disqualification are stricter than ISO. The origin test, by contrast, is absolute: no permitted percentage, no de minimis threshold, no exception for good bought-in regrind. PE-X is excluded even from own-rework reuse, because crosslinked polyethylene behaves like a thermoset and cannot be melted back into pipe: the crosslinks that give PE-X its temperature performance are the same bonds that stop the scrap re-entering an extruder. That exclusion attaches to cross-linked polyethylene pipe generally, wherever it is made. It is worth being precise about what we ourselves sell here, because the distinction is easy to blur: our 2114 and 2121 PEX fitting ranges are brass fitting systems for PEX installations — 2114 card-sleeve compression in S16 and S20, offered in brass, chrome and electroplate finishes, and 2121 press/crimp in 16, 18, 20, 25, 26 and 32 mm (per our catalogue) — not PE-X pipe grades. The ISO 15494 rework question does not arise for them in the first place; a machined brass fitting is a different material stream with a different set of questions.

What does not appear: any percentage figure. We found no numerical cap on rework in PP-R or PE pressure pipe anywhere in the accessible standards text — ISO 15494 clause 5.4 and PPI TN-30 both regulate rework qualitatively, by origin, cleanliness, documented procedure and equal-or-better strength rating. A supplier quoting “the standard allows up to 15% regrind” is quoting something that, so far as we could verify, is not in the standard.

A sourcing disclosure. ISO 15874-1:2013 is the standard actually governing PP-R hot and cold water piping, and it does contain a material clause 5.3 titled “Reprocessable material” — confirmed from the official preview (2nd edition, prepared by CEN/TC 155 with ISO/TC 138/SC 2 under the Vienna Agreement). But that preview truncates before clause 5, so we could not read 5.3 itself. The wording quoted above is verbatim from the sister pressure standard ISO 15494:2015, which uses the same wording family; we are not presenting it as a quotation of ISO 15874. If your specification turns on the exact ISO 15874 wording, buy the standard and read clause 5.3 directly.

Where Recycled Pipe Legitimately Exists

The industry is not hostile to recycled content; it puts it where failure consequences are survivable. Zoran Davidovski of Pipelife, a TEPPFA member company, in a technical interview: “We only use recycled materials in non-pressure applications; in pressure applications, it is not allowed.” The same interview notes content “can be up to 100% recycled material, depending on requirements.”

TEPPFA’s circular-economy material says “the majority of the plastic pipes recycled feedstock volumes go into high quality below ground stormwater and sewage pipes as well as cable ducts”, and that it is “either being mixed with virgin material or coextruded in the middle layer of the plastic pipe.” Even where recyclate is welcome it is often confined to a sandwich layer between virgin skins, carrying structural bulk rather than the hydraulic or weathering surface. One attribution caution: TEPPFA itself makes no pressure/non-pressure prohibition statement; that quote is Pipelife’s, a member company, not the association.

This bears on our range: our PVC 902 drainage line (pipe Φ32–110, with the 1902 fittings series running to Φ160) is a non-pressure product per our catalogue — the family where recycled content is a legitimate engineering choice industry-wide — while our PPR PN20, UPVC/CPVC 806 PN16 and HDPE PN16 lines (per our catalogue) sit where the origin rule is absolute.

Why It Matters: The Mechanism, Not the Slogan

Buyers usually get the conclusion — “recycled material weakens pipe” — without the mechanism, which makes it sound like prejudice. It is specific.

The rating is a statistical floor, not a typical value. ISO 9080:2012 clause 1 specifies a method for predicting long-term hydrostatic strength “by statistical extrapolation”; clause 0.3 states what that method produces — the “lower prediction limit (at 97,5 % probability level) of the stress which a pipe made of the material under consideration is able to withstand for 50 years at an ambient temperature of 20 °C”. The number on the pipe is already the pessimistic edge of the distribution — so degradation from uncontrolled feedstock does not eat into a comfortable safety factor, it eats into the statistical margin the rating is built from. (Sourcing note, held to the same standard as the ISO 15874 disclosure above: unlike ISO 15874-1, whose official preview truncates before its material clause, the ISO 9080:2012 preview published by ISO carries the Introduction and Scope in full, so this wording was confirmed word-for-word against the primary document rather than a secondary restatement.)

The failure mode is the ductile-to-brittle knee. PPI TN-7: “These polyolefin materials may exhibit a change in failure mode from ductile to brittle, or slit failures. This change in failure mode typically decreases the material’s long-term strength as the slope of the regression line changes in the brittle zone.” And: “Higher temperatures shorten the time-to-failure and the time to ductile-brittle failure mode transition (i.e. Arrhenius relationship).” That is why hot-water PP-R is the sensitive case rather than cold-water PVC — and why ISO 9080:2012 carries a normative Annex B, “Automatic knee detection”.

The controlling chemistry is antioxidant depletion. Apostolov and Djoumaliisky (Materials Sciences and Applications 5:579–591, 2014) identify thermo-oxidative degradation as “the main factor that substantially decreases the service life of the tubes and fittings” for PP pipe, and state that “The thermal oxidation stability of PP depends directly on the type and quantity of antioxidants used”. The chain: antioxidant protects the polymer; every heat history consumes some; feedstock with unknown thermal history carries an unknown remaining reserve; depleted stabiliser accelerates degradation; degradation moves the knee earlier; that erodes the 97.5% extrapolation the 50-year rating rests on. What is at stake, per ISO 9080 testing reported in the Wefatherm manual (Tables 2.8/2.9): PP-R (Borealis RA130E) is MRS 10 MPa at 20 °C / 50 years but CRS 3.2 MPa at 70 °C / 50 years; PP-RCT (Borealis RA7050) is MRS 11.5 MPa and CRS 5 MPa on the same basis. (That source’s own graphic labels PP-RCT “MRS 11,2 MPa”, an internal inconsistency, so cite 11.2 vs 11.5 with care.) How far the figures fall between 20 °C and 70 °C is the temperature sensitivity, expressed as design stress.

PPI TN-30 (2013 Edition) turns this into a rule. §3.3: “Rework materials must originate in the manufacturer’s own pipe production facilities.” and “Materials from other outside sources are prohibited.” §3.2 makes it one-way — rework must have “the same or higher PPI listed Hydrostatic Design Stress (HDS) at 73°F … as the virgin material with which it is used”. Most revealing is §3.4, listing pipe unsuitable for rework: “Unknown thermal history”; “Excessive melt temperature that may cause degradation contamination”; “Non-black polyethylene pipe stored outdoors for over two years from date of manufacture”; “Rework pipe that cannot be cleaned”. Read that as a description of post-consumer recyclate and the prohibition explains itself — recyclate carries every disqualifier by definition. (TN-30’s scope is ASTM D2513 PE gas pipe; we cite it as convergent reasoning on rework control, not as a document governing PP-R.)

What a Buyer Can Actually Test For

Here we disappoint a common expectation. No test hands you a percentage. We found no authoritative source giving a validated method to back-calculate recycled content in finished pipe; FTIR, DSC secondary melt peak, TGA ash and melt flow are described in commercial laboratory material as contamination and identification screens, qualitatively. What you can test for is indicators of degraded or contaminated feedstock — more honest, and still useful.

OIT (oxidation induction time) by DSC is the practical incoming-QC test for depleted stabiliser. The procedure used by Apostolov and Djoumaliisky for PP pipe: sample in an open aluminium pan, empty pan as reference, heated under nitrogen to 200 °C, held isothermally one minute, then atmosphere switched to oxygen at 50 ml/min; OIT is the lag from start of isotherm to onset of exotherm. Test standard family: DIN EN 728 / ASTM D3895. Two cautions: the commonly quoted 200 °C (PE) / 210 °C (PP) temperatures reached us via a test-equipment vendor rather than standard text, and we could not confirm whether EN 728 is superseded by EN ISO 11357-6. The widely cited 20-minute minimum OIT is attributed to ASTM D3895 through a secondary citation; we found no minimum OIT acceptance value specific to PP-R plumbing pipe in EN ISO 15874, so do not write that threshold into a specification and attribute it to ISO 15874.

Why OIT alone can be gamed. Knoben et al. (Materials 18(7):1640, 2025) reprocessed PP five times and tracked oxidative stability across the cycles. Without antioxidant re-dosing, that stability fell monotonically cycle on cycle, alongside “an exponentially increasing MVR trend” indicating chain scission. But closed-loop recycling with antioxidant re-dosed each cycle produced “significant build-up of AOs” and “OIT values in closed-loop samples from the rigid PP … higher overall”. Re-stabilised recyclate can therefore read high on OIT: it measures remaining protection, not accumulated damage. Pair it with MFR/MVR — antioxidant can be topped up, but a shortened molecular chain cannot be put back. (The five-cycle figure is a lab design choice, not a regulatory limit; no standard we found caps reprocessing cycles.)

A note on how we are citing that study. Our working copy of the declining-stability result records it in degrees Celsius, which does not match the isothermal OIT defined two paragraphs above — OIT is a time, in minutes. A Celsius range points instead to oxidation onset temperature (OOT), the dynamic ramped-DSC measurement, which is a related but distinct experiment. Rather than guess which quantity the authors reported, we have stated only the direction of travel, which is not in doubt and is all the argument requires. If you plan to put a specific number from that paper into a specification, read it directly and confirm the unit first.

The Document to Demand Instead

Since no test reports a percentage, leverage moves to the paperwork. The Wefatherm PP-R Specification Manual (2024), listing §4.3/4.4 requirements for DVGW fitness-for-purpose certification, includes: “Confirmation of the producer that exclusively virgin material and no other material is used in the production process”, alongside ISO 9001 certification and third-party testing.

So the ask is not “do you use recycled material?” — which invites reflexive denial — but “provide the producer declaration of exclusively virgin material that a third-party certification body would require, and name the body it was issued to.” A declaration addressed to a named notified body carries consequences a sales email does not. Then: which category does the wall contain? Is the compound qualified to ISO 9080, at which MRS/CRS class? And if in-house rework is used, what documented procedure controls its origin and formulation traceability? (Our own experience-based view, not a standards requirement: a written procedure separates controlled rework from casual regrind more reliably than any single test result.)

We are aware of what we have just recommended. A producer declaration of exclusively virgin material is a stricter test than our own PPR practice would pass — we disclose in-house regrind at ≤10%, and “exclusively virgin” admits none. We are pointing you at a yardstick we do not currently clear on that line. Two things are true at once: ISO 15494 clause 5.4 permits own-plant rework in addition to virgin material, so controlled regrind is a conforming choice rather than a defect; and a DVGW fitness-for-purpose route sets a higher bar than the ISO baseline, because certification schemes are free to be stricter than the standards they build on. If your project is specified to that DVGW route, the honest answer is that you should ask for the virgin-only declaration and hold every supplier to it, ourselves included. Recommending only the tests we happen to pass would make this article a sales document rather than a useful one.

Our Own Position, Including the Awkward Part

Our catalogue says, of PPR PN20, that recycled material is ≤10% and quality is unaffected; the range is PPR PN20 1103 pipe in 20×2.8, 25×3.5 and 32×4.4 mm only, 4 m lengths, with a 75-item 1138 fittings series (per our catalogue).

Now the awkward part, which we would rather write ourselves than have a buyer find in technical review. The standards we could open contain no 10% figure, or any percentage figure. So our “≤10%” is a self-imposed internal ceiling described in our own commercial documentation — not compliance with a numerical standards limit, and not a limit any standard endorses. We are not going to dress a company policy up as a clause number.

The next question a technically literate buyer asks is the right one: ≤10% of what category? The category question governs, and we will not answer it in a blog article with a claim we cannot document. What is verifiable today: our plant is Zhuji Fengfan Piping in Zhejiang — 30+ years, 1000+ employees, 118+ countries, 120,000 m² (per our catalogue). Certifications include SKZ, CE, WRAS, DVGW, SGS, ISO 9001 and ISO 14001, with certificate numbers and scope detail Coming soon. A material declaration in the form DVGW certification requires, tied to a named certificate, is Coming soon, as is published per-batch OIT and MFR data for PPR feedstock — though that can be raised for a specific order enquiry.

Two further limits, since this article is about credibility. We cannot supply DN150–400 main-line pressure pipe: our ceiling is Φ110 and PPR stops at 32 mm (per our catalogue, set out size by size in our pipe sizing charts). If your project needs mains, we are the wrong supplier for that line item. And IFANNova is a French brand; the pipe is manufactured in Zhejiang, China. We will not imply otherwise, on this subject least of all — a supplier vague about where the pipe is made has no standing to ask you to trust them about what is in it. In the same spirit: our HDPE PN16 pipe body is marked “GERMANY STANDARD DIN8077/8078” (per our catalogue), but that numbering is in fact the PP standard family — the PE equivalents are DIN 8074/8075. We report the marking and do not claim conformity to it.

What This Means for Your Next Enquiry

Ask about category, not percentage — the framework is built on origin, and the percentage question has no standards answer we could find. Pair OIT with MFR/MVR, because OIT alone can read high on re-stabilised recyclate. Get the virgin-material declaration in writing and addressed to a certification body: it is the one artefact obtainable without a laboratory.

And separate your pressure lines from your drainage lines before the conversation starts. Recyclate in a buried non-pressure stormwater pipe is a legitimate engineering choice the industry is expanding; recyclate in a hot-water pressure riser is a different question with a different answer. Suppliers who blur the two — in either direction — make the conversation harder than it needs to be.

Where to Go Next

• PPR Pipe & Fittings — the PN20 1103 range (20/25/32 mm) and the 75-item 1138 fittings series, with the size ceiling stated up front.
• Quality Control — the in-house pressure, temperature, material and dimensional testing referenced above, and the third-party inspection route.
• Sustainability — our regrind disclosure, recyclability and ISO 14001, stated without green slogans.
• Potable water approval for the GCC — what WRAS, DVGW, ACS and NSF/ANSI 61 actually cover, and what they do not.
• Pressure testing plastic pipe — why a falling gauge is often creep rather than a leak.
• PVC 902 Drainage (pipe Φ32–110, fittings to Φ160, non-pressure) · Certifications · HDPE Pipe & Fittings

If you want this answered for a specific order rather than in general, send us the line items and destination market and we will tell you what we can document today and what is still Coming soon — including where we are not the right supplier. Contact IFANNova.