Get the numbers wrong and you pay for it twice. Spec a cold-rated pipe onto a hot-water line and you risk a burst and a rework bill; over-spec a cold line with the thickest class and you tie up cash in wall thickness you did not need. This guide explains PPR pipe specifications in plain terms — what PN10, PN16, PN20 and PN25 actually mean, how to read pipe sizes and wall thickness, how to choose the right class for cold versus hot water, and why a pipe’s safe pressure drops as the water gets hotter.
One note before the tables. The values below are typical industry reference figures, given for general orientation — they are not a WARMHAUS-specific product promise. When you spec a real project or place a container order, always confirm the exact PN classes, dimensions and certifications against the manufacturer’s technical datasheet (TDS). At the end of the guide we show how to get certified, project-ready PPR specifications for the Middle East, North Africa, Southern Europe and Latin America.
I. What Is PPR Pipe?
PPR (Polypropylene Random Copolymer) is a rigid thermoplastic used for hot and cold water supply. Its defining feature is how it is joined: pipe and fittings are heat-fused (hot-melt welded) into a single continuous piece — no glue, no threaded metal joint to corrode or leak. Because it is plastic, PPR is immune to corrosion and scaling, and it carries a long design life — commonly cited around 50 years as a general industry figure — at a mid-market cost.
That combination is why PPR is the mainstream hot-and-cold water system across the Gulf, North Africa, Southern Europe and Latin America. If you are still weighing materials, see our comparison of PPR vs PEX vs copper vs PVC. To spec PPR correctly, you need to read three things on every pipe: its PN class, its size, and its temperature limit — which the rest of this guide breaks down.
II. What Does PN Mean? PN10, PN16, PN20 & PN25 Explained
PN stands for “Pressure Nominal” — the nominal pressure, in bar, that a pipe is rated to safely handle at a reference temperature of 20 °C. It is the single most important number on a PPR pipe. The higher the PN class, the thicker the wall and the higher the pressure and temperature the pipe can take. Here is what each common class generally means:
| PN class | Nominal pressure @ 20 °C | Relative wall thickness | Typical use (general industry guidance) |
|---|---|---|---|
| PN10 | ~10 bar | Thinnest | Cold water distribution only |
| PN16 | ~16 bar | Medium | Cold water, higher-pressure cold lines |
| PN20 | ~20 bar | Thick | Hot & cold water supply — the common all-round class |
| PN25 | ~25 bar | Thickest (often fibre-reinforced) | Hot water, heating, high pressure/temperature |
Two takeaways buyers rely on. First, PN is a “cold” rating — that headline bar figure assumes 20 °C water, and the safe pressure drops as the water gets hotter (see the temperature–pressure section below). Second, for the same outside diameter, a higher PN has a thicker wall and therefore a narrower bore — so moving from PN10 to PN25 in the “same size” pipe actually reduces the internal flow area. That is why the drawing specifies both a size and a PN class.
Download the PPR PN Selection Chart
III. PPR Pipe Sizes & Wall Thickness Chart
PPR pipes are specified by outside diameter (OD) in millimetres. The most common range runs from 20 mm to 110 mm, with larger diameters available for mains and risers. For any given OD, the wall thickness increases with the PN class, so the same “size” pipe comes in several wall thicknesses depending on the pressure rating you choose.
Typical industry reference values — confirm exact dimensions on the manufacturer’s TDS before you spec or order.
| Nominal size | Outside diameter (OD) | Common uses | Wall thickness note (general) |
|---|---|---|---|
| DN15 | ~20 mm | Branch lines to fixtures | Increases from PN10 → PN25 |
| DN20 | ~25 mm | Fixture supply, small branches | Increases from PN10 → PN25 |
| DN25 | ~32 mm | Main branches | Increases from PN10 → PN25 |
| DN32 | ~40 mm | Risers, larger branches | Increases from PN10 → PN25 |
| DN40 | ~50 mm | Risers, distribution | Increases from PN10 → PN25 |
| DN50 | ~63 mm | Mains, risers | Increases from PN10 → PN25 |
| DN65 | ~75 mm | Mains | Increases from PN10 → PN25 |
| DN80 | ~90 mm | Mains, larger systems | Increases from PN10 → PN25 |
| DN100 | ~110 mm | Large mains, commercial | Increases from PN10 → PN25 |
Note that DN (nominal diameter) and OD are two ways of labelling the same pipe — trade practice often quotes the OD in mm (e.g. “PPR 25” means 25 mm OD), while drawings may use DN. Match both the size and the PN class from the drawing, and remember: a higher PN in the same OD means a smaller inner bore, which affects flow. WARMHAUS supplies its exact OD, wall thickness and PN dimensions per product line on request — see the WARMHAUS PPR pipe range.
IV. Cold vs Hot Water: Which PN Class to Choose
The most common real-world question buyers ask is simple: cold or hot — which PN do I need? The rule of thumb, as general industry guidance, is that hotter water needs a higher PN class because heat lowers a pipe’s safe working pressure. Here is the practical mapping most markets follow:
| Application | Typical PN class (general guidance) | Why |
|---|---|---|
| Cold water only | PN10 | Thinner wall is sufficient when water stays cool (distribution, garden, low-pressure) |
| Cold water, higher pressure | PN16 | Extra wall for higher cold-line pressure (tall risers, boosted systems) |
| Hot & cold water supply | PN20 | The versatile default — handles both hot and cold general plumbing |
| Hot water, heating, high temp/pressure | PN25 (often fibre-reinforced) | Thickest wall; fibre layer limits thermal expansion |
For most projects and distributor catalogs across the Gulf, North Africa, Southern Europe and Latin America, PN20 is the workhorse for hot-and-cold supply, with PN25 added for hot-water and heating circuits, and PN10 kept for cold-only lines. Fibre-reinforced PN25 — a stabilised composite layer in the wall — is worth knowing about because it reduces thermal expansion on long hot lines, a common spec on heating and high-temperature runs. Confirm the exact class the drawing calls for; never substitute a lower PN on a hot line to save cost.
V. The Temperature–Pressure Relationship (Why PN Is a “Cold” Rating)
This is the concept that trips up most first-time buyers: a pipe’s PN rating is not its pressure limit at every temperature. PN is defined at 20 °C. As the water gets hotter, the polypropylene softens slightly and its long-term strength falls, so the safe working pressure drops — a PN20 pipe carrying 70 °C hot water safely handles noticeably less than 20 bar over its design life, not the full “20” on the label. This is a general property of thermoplastic pipe, described by long-term strength (regression) curves in the product standards.
The number on the pipe is a 20 °C rating. The hotter the water, the less pressure the pipe can safely carry — which is exactly why hot lines wear a higher PN.
Two practical consequences for anyone specifying PPR:
- Hot lines need a higher PN than cold lines of the same size. The extra wall thickness of PN20/PN25 compensates for the strength lost to heat, so the line still meets its target pressure at operating temperature over the full ~50-year design life.
- Both temperature and design life matter, not just pressure. Pipe standards rate PPR against a combination of temperature, pressure and time. That is why you spec a PN class for the application, and confirm the real allowable working pressure at your operating temperature on the manufacturer’s TDS — not off the headline PN number alone.
VI. How to Choose the Right PPR Pipe: A 4-Step Spec Checklist
Pulling it together, here is the short checklist buyers, projects and installers use to spec PPR correctly — turn it into a repeatable habit before every quote or order:
Application — hot, cold, or heating?
Decide what the line carries. Hotter service always points to a higher PN class, because heat lowers the pipe’s safe working pressure.
Pressure — which PN class?
Match the pressure at operating temperature to the class: PN10 (cold only) · PN16 (higher-pressure cold) · PN20 (all-round hot & cold) · PN25 (hot, heating, high pressure — often fibre-reinforced).
Size — OD/DN from the drawing
Read the size the drawing calls for and quote it consistently: OD in millimetres (20–110+ mm) matched to its DN label. Remember the bore narrows as PN rises in the same OD.
Compliance — what must be documented?
Confirm the certifications the market or project requires — ISO, SKZ, DVGW and destination-market documents — and ask the manufacturer for the technical datasheet that proves them.
Do steps i–iii off the drawing and this guide; step iv is where a supplier makes or breaks the deal. A project engineer or a customs officer will ask for certifications and a technical datasheet, not a blog table. That is the point at which you want a manufacturer who can hand you tested PN classes, exact dimensions and certificates — which is what a certified Italian PPR maker provides.
VII. Need Certified PPR Specifications? Ask an Italian Manufacturer
This guide gives you the general rules — PN classes, sizes, and the temperature–pressure relationship. For a real quote, project spec, or container order, you need tested figures and certificates, and that is where WARMHAUS comes in. We are an Italian manufacturer of PPR water systems — plus PEX underfloor heating and brass valves and fittings, over 270 SKUs from one source. Made in Italy in Bologna since 1970, ISO 9001 / ISO 14001 / SKZ / DVGW certified. We supply PPR pipe technical datasheets with PN classes, dimensions and certifications for importers, projects and private-label partners across the Middle East, North Africa, Southern Europe and Latin America.
Tell us your market and the sizes and PN classes you need, and we will send PPR specifications, certifications and distributor terms. Exact wall thickness per size, MOQ, lead times, pricing and certificate numbers — available on request.