Polyethylene (PE) pipe carries water, gas, sewage and industrial fluids above and below ground. Two codes printed on every length set how it performs: PN, the pressure rating in bar, and SDR, the outside diameter divided by the wall thickness. Most pressure pipe used in Australia is PE100, the third-generation grade rated for 100 years or more of service.
Reading the pipe: colour, PN, OD and SDR
Every PE pipe is marked with what you need to install it correctly. The stripe tells you what it carries; the printed codes tell you how much pressure it holds and how thick the wall is.
Colour codes
A coloured stripe is extruded into the pipe wall as a permanent marker of contents.
Stripe
Blue
Red
Lilac
Yellow
Green
Cream
Carries
Potable water
Fire mains
Recycled / grey water
Gas
Rain water / raw water
Sewer
PN — pressure rating
PN stands for Pressure Nominal: the internal pressure the pipe is designed to hold, in bar. A PN16 pipe handles 16 bar. Blue-stripe potable water pipe is usually PN16.
Rating
PN10
PN12.5
PN16
Max Pressure
1000 kPa
1250 kPa
1600 kPa
OD — outside diameter
OD is the outside diameter in millimetres, printed on the pipe. Australian PE pipe started at diameters like 20, 32 and 63 mm; it now runs up to 2000 mm.
SDR — standard dimension ratio
SDR is the outside diameter divided by the wall thickness. A lower SDR means a thicker wall relative to the diameter, and a higher pressure rating. OD, SDR and PN work together: for a given diameter, the wall thickness sets both the SDR and the PN.
What PE is
Polyethylene is one of the most widely produced thermoplastics in the world. The process behind it was developed in the 1950s by Karl Ziegler and Giulio Natta. It is light, strong, cheap to transport and safe to handle and store.
PE grades
Grade
LDPE
HDPE
UHMW PE
What it is
Low-density‚ flexible‚ high ductility‚ low tensile strength
High-density‚ moderately stiff‚ tough‚ highly crystalline
Extremely dense; tensile strength many times that of steel
Typical use
Plastic film‚ shopping bags
Containers‚ plumbing‚ pressure pipe
Bulletproof vests‚ high-wear parts
Pressure pipe for water, waste water and gas uses a specific HDPE grade: PE100.
Thermoplastic, not thermoset
PE is a thermoplastic – it can be heated to melting, cooled and reheated without degrading. That is what lets PE pipe be joined by fusion: butt fusion and electrofusion melt and reform the material into one continuous part. Thermoset plastics set on first heating and cannot be reworked.
Why PE100
PE100 is the third-generation PE pressure-pipe grade. It balances three properties:
- Minimum Required Strength (MRS) – long-term strength and creep resistance
- Slow crack growth resistance
- Rapid crack propagation resistance
PE100 has a proven MRS of 10 MPa at 50 years and 20°C. Service life runs to 100 years or more, depending on raw material quality, processing, installation, the fluid carried, and operating pressure and temperature.
PE100 properties
Property
Minimum Required Strength (MRS)
Hydrostatic Design Basis (HDB)
Allowable compressive strength
Tensile strength at yield
Elongation at break
Modulus of elasticity (50 years)
Flexural modulus
Poisson’s ratio
Thermal expansion coefficient
Friction – Colebrook-White
Friction – Hazen-Williams
Friction – Manning
Value
10.0 MPa (1450 psi)
1600 psi (11 MPa)
7.93 MPa
23 MPa
>600%
200 MPa
1000 MPa
0.45
1.3 × 10⁻⁴ °C⁻¹
0.00152 mm
150–155
0.009 (water) / 0.010 (sewage)
These values are measured at 20–23°C and fall as temperature rises, MRS included.
Abrasion resistance
PE100 has the best abrasion resistance of the common pressure pipe types. It matters most in wastewater rising mains, where transported solids wear the pipe invert. Straight runs see abrasive erosion; bends and size transitions see both abrasive erosion and impact abrasion.
PE100 variants
Variant
PE100 RC
PE100 RT
Barrier PE
Co-extruded PE
What it adds
Resistance to cracking — higher slow-crack-growth resistance at the same MRS. Type 1 solid wall; Type 2 integrated protective layer; Type 3 outer casing over a PE100 RC inner.
Resistance to temperature — holds mechanical properties at higher temperatures.
Co-extruded barrier layer (usually aluminium foil‚ sometimes EVOH) to stop gases and liquids permeating the wall.
Multi-layer builds: internal or external coatings‚ and conducting layers or strips.
Where it is used
Types 1 and 2 for open trench without sand bedding; Type 3 for trenchless.
Consistent service above 50°C: hot water and industrial. Rare in buried water or gas.
Potable water in contaminated ground.
Leak monitoring and pipe detection.
Applications
PE100 conveys liquids and gases above and below ground, including:
- Urban water and gas supply
- Mine dewatering
- Irrigation supply
- Slurry pipelines
- Vacuum, pressure and gravity sewer systems
- Submarine pipelines and ocean outfalls
- Trenchless installation and rehabilitation
- Industrial process pipework
- Compressed air services
- Electrical and telecommunication cable conduits
- Upstream coal seam gas and water pipelines
Durability and recycling
PE pipe resists corrosion, absorbs ground movement, and outlasts metallic pipe. It is also recyclable: HDPE can be recycled at least 10 times without losing strength, and shredding and injection moulding do not alter its properties over that period. PLASSON recycles 97% of the waste stream from its factories. With a service life near 100 years, the material can be repurposed for centuries.
Assessing risk of failure in PE water mains
Polyethylene potable water mains with an assumed minimum design life of 50 years have been in widespread use in the water industry for more than 30 years.
In the 1980s and 1990s, Severn Trent Water in the UK buried two polyethylene pipe test beds in the Midlands. These two test beds near the pumping stations at Great Gates and Coopers Green, had all the pipe material analysed chemically and mechanically before installation. This was documented in several studies as well as the subsequent exhumations in the following years.
These reports showed that the pipe had not deteriorated significantly in the first 5 years after installation.
These pipes have been exhumed, and the tests repeated 30 years later. Analysis of these pipes showed that some of the newest PE100 pipes could last as long as 160 years. The variation in performance of early pipes compared to newer evolutions was also obvious from the results obtained.
As of 2020, PE pipe is being used for more that 95,000km of the UK’s drinking water pipe network, and 90% of new water mains being laid utilise polyethylene.
FAQ
What does PN mean on poly pipe?
PN (Pressure Nominal) is the internal pressure the pipe is rated for, in bar. PN16 is rated for 16 bar.
What is SDR?
SDR (Standard Dimension Ratio) is the outside diameter divided by the wall thickness. A lower SDR means a thicker wall and a higher pressure rating.
What is PE100?
PE100 is the third-generation HDPE pressure-pipe grade, with a minimum required strength of 10 MPa and a service life of 100 years or more.
What do the stripe colours mean?
Blue is potable water, red is fire mains, lilac is recycled water, yellow is gas, green is rain or raw water, and cream is sewer.
How long does PE pipe last?
Up to 100 years, depending on material quality, installation, and operating pressure and temperature.
