HDPE & PVC Pipe Industry Glossary
50 plain-English definitions covering the HDPE and PVC pipe industry — material grades, pressure classes, joining methods and certification standards.
HDPE
— High-Density Polyethylene- A thermoplastic polymer with a high strength-to-density ratio, made from petroleum. Used for water mains, gas distribution, mining slurry lines and chemical-resistant industrial piping. Service life of 50–100 years; joined by butt fusion or electrofusion.
- → HDPE Water Supply Pipe
PVC
— Polyvinyl Chloride- A rigid thermoplastic widely used for water supply, drainage, irrigation, electrical conduit and industrial chemical transport. Cheaper than HDPE but more brittle; joined by solvent-weld socket or threaded fittings.
- → PVC Water Pipe
PPR
— Polypropylene Random Copolymer- Thermoplastic used primarily for hot and cold potable water plumbing inside buildings. Joined by socket fusion. Service temperature up to 70 °C continuous, 95 °C intermittent.
CPVC
— Chlorinated PVC- PVC modified with extra chlorine for higher heat resistance — works at up to 90–95 °C, suitable for hot water, chemical processing and electroplating lines.
- → CPVC Pipe
PE100
- The current-generation HDPE resin grade with Minimum Required Strength (MRS) of 10 MPa at 20 °C over 50 years. Most modern pipes are PE100; PE80 is older and only used for legacy projects.
PE80
- Earlier-generation HDPE resin with MRS 8 MPa. Replaced by PE100 in most markets but still seen in some legacy or low-pressure applications.
PE4710
- ASTM D3350 cell-class designation for high-performance HDPE — equivalent to PE100 in stress crack resistance and hydrostatic strength. Used in US and Canadian water and gas markets.
PE100-RC
— Resistance to Crack- Enhanced PE100 with > 8,760 h Notch Pipe Test resistance (vs ~165 h for standard PE100). Allows trench-less installation, sand-bed-free laying and fewer crack failures from point loads.
SDR
— Standard Dimension Ratio- The ratio of outer diameter to wall thickness (OD ÷ wall). Lower SDR = thicker wall = higher pressure rating. Common values: SDR 7.4, SDR 9, SDR 11, SDR 13.6, SDR 17, SDR 21, SDR 26.
- → How to Select HDPE Pipe SDR
PN
— Pressure Nominal- Working pressure rating in bar (1 bar ≈ 14.5 psi). For PE100 at 20 °C water: SDR 11 → PN 16, SDR 17 → PN 10, SDR 26 → PN 6. Derate for higher temperatures, surge and chemical service.
DN
— Diameter Nominal- ISO designation for pipe outer diameter in millimetres — e.g. DN110, DN160, DN315. Plastic pipes are categorised by DN (OD-based) rather than nominal-bore in inches.
OD / ID
— Outer / Inner Diameter- OD is fixed for a given DN; ID changes with wall thickness (which depends on SDR). For DN110 SDR 11: OD = 110 mm, wall ≈ 10.0 mm, ID ≈ 90 mm.
MRS
— Minimum Required Strength- The 50-year hydrostatic strength of a polyethylene grade in MPa. PE80 = 8.0 MPa; PE100 = 10.0 MPa; PE100-RC matches PE100 but adds notch-resistance.
Butt Fusion
- HDPE joining method: pipe ends are heated against a hot plate, then pressed together to fuse. Produces a joint stronger than the parent pipe. Best for DN ≥ 90 mm and clean above-ground or trench conditions.
- → Butt Fusion vs Electrofusion
Electrofusion
- HDPE joining method using a saddle / coupler with embedded heating coils. An EF welder applies controlled voltage to melt the polymer; the joint is logged for traceability. Best for confined spaces, repairs and small-diameter work.
- → HDPE Electrofusion Fittings
WRAS
— Water Regulations Advisory Scheme- UK certification confirming a product is safe for contact with potable water. Required for water mains and plumbing fittings in the UK; widely recognised in former British Commonwealth markets.
NSF 61
- American National Standard for materials in contact with drinking water. Mandatory for plumbing products in the US and Canada; tests for leached metals, organics and additives.
ISO 4427
- International standard for PE pipes and fittings used in water supply. Specifies dimensional tolerances, pressure classes and material requirements for PE80 and PE100.
ASTM F714
- US standard for HDPE pipes (DN ≥ 90 mm) based on outside diameter. Specifies dimensions, pressure ratings (DR) and quality requirements for water, sewer and industrial use.
AWWA C906
- American Water Works Association standard for polyethylene pressure pipe (DN 100 mm – DN 1600 mm) used in municipal potable water. Companion to AWWA C901 (smaller diameters).
RoHS
— Restriction of Hazardous Substances- EU directive limiting the use of lead, cadmium, mercury and other hazardous substances in electrical and electronic products. Required for electrical conduit and accessories sold in the EU.
Slurry Pipe
- Pipe carrying solid–liquid mixtures (mineral concentrates, tailings, dredged material). Demands abrasion resistance — HDPE PE100 is preferred over steel because of low surface friction and 5–10× longer wear life.
- → HDPE Mining Pipe
Dredging Pipe
- HDPE pipe used in floating or submerged dredge lines to convey sand, mud and slurry. Lightweight, abrasion-resistant; supplied with pre-installed steel flanges for fast field connection.
- → HDPE Dredging Pipe
Coil
- HDPE supply form for small diameters — pipe is wound onto a drum (typical lengths 50 m / 100 m / 150 m / 200 m). Reduces field joints, transport cost and installation time vs straight 6 m / 12 m sticks.
Flange
- Mechanical joining method: a pipe stub end is bolted via a backing ring to another flange. Used to connect HDPE to steel valves, pumps or dissimilar materials, and where future disassembly is required.
- → HDPE Flanges
ASTM D3035
- US standard for PE pipes (small / medium diameter, ≤ DN 110 mm) sized by outside diameter. Companion to ASTM F714 (large diameter). Defines wall thickness, pressure rating and quality requirements for water and industrial service.
ASTM F2620
- US standard procedure for butt fusion of polyethylene pipe and fittings. Specifies heater temperature (400–450 °F), interfacial pressure, heat-soak time and cool-down — followed by every certified HDPE installer in North America.
- → Butt Fusion vs Electrofusion
BS EN 12201
- European harmonised standard for PE pipe systems used in water supply (cold drinking water and other uses). Covers PE100 and PE80 pipes, fittings and valves. Aligns with ISO 4427 with European-specific testing.
GB 15558
- Chinese national standard for buried polyethylene gas distribution pipes (yellow / black with yellow stripe). Specifies dimensions, pressure ratings up to 10 bar, and electrofusion-only jointing for safety-critical gas mains.
AS/NZS 4130
- Australia / New Zealand standard for PE pipes for pressure applications — water, gas, mining slurry. Adopts ISO 4427 with regional climate and material variations; widely cited in Australian and Oceania tender specifications.
Hydrostatic Test
- Pressure-integrity test in which the pipe is filled with water and pressurised to 1.25–1.5× design working pressure for a set hold time. Used at the factory (QC), pre-commissioning (acceptance) and periodically in service.
Carbon Black
- Finely dispersed soot pigment compounded into HDPE (≥ 2% by mass) for UV stabilisation. Reason black HDPE pipes outlast coloured ones above ground — black absorbs UV, carbon black prevents the polymer chain breakdown that would follow.
Creep
- Slow long-term deformation of plastic under sustained load. The reason every plastic pipe has a derating curve at elevated temperature and long time horizons — design stress drops to ~ 8 MPa at 50 years for PE100, not the short-term 25 MPa.
RCP
— Rapid Crack Propagation- Catastrophic failure mode in which a small initial crack runs the length of a pipeline at speeds > 100 m/s. Avoided by selecting PE100 / PE100-RC with adequate critical temperature (Tc) for the operating climate.
SCG
— Slow Crack Growth- The dominant long-term failure mode of PE pipes — a slow stable crack propagates from a stress concentrator (notch, point load) over months / years. PE100-RC's enhanced crack resistance specifically targets this mechanism.
- → PE100 vs PE100-RC
MFI
— Melt Flow Index- Resin processing index measured in g/10 min — how easily molten PE flows through a standard die under load. PE100 pipe grades typically fall in 0.2–0.4 g/10 min; lower MFI generally means higher molecular weight and better long-term performance.
HDD
— Horizontal Directional Drilling- Trenchless installation method: a guided drill bore is created from a launch pit, the pipe is then pulled back through the bore. Used to cross roads, railways, rivers and built-up areas without surface disruption.
- → HDPE Installation Methods
Pipe Bursting
- Trenchless replacement method in which a bursting head fragments an old pipe (cast iron, AC) while pulling a new HDPE pipe of equal or larger diameter into the same alignment. Avoids open-cut excavation of streets.
Sliplining
- Trenchless rehabilitation method: a smaller HDPE pipe is inserted inside a deteriorated host pipe, then grouted in the annulus. Restores hydraulic capacity in iron / concrete mains without dig-and-replace cost.
Pipe Bedding
- The graded sand or fine aggregate placed underneath and around a buried pipe to provide uniform support and prevent point loads. PE100-RC's enhanced crack resistance allows direct-burial without traditional sand bedding.
Tee
- 3-way fitting that splits flow into a perpendicular branch. Equal tees have the same DN on all 3 ports; reducing tees have a smaller branch. Available in butt-fusion, electrofusion or flanged configurations.
- → HDPE Tee
Elbow
- Pipe direction-change fitting, typically 90° or 45°, sometimes 22.5°. Made by injection moulding (small DN) or fabricated from mitre-cut segments (large DN). Critical thrust restraint required at large elbows on pressure mains.
- → HDPE Elbow
Reducer
- Fitting that connects two different DN sizes. Concentric reducers share a common centreline; eccentric reducers share a common top or bottom (used in pump suction lines to avoid air pockets).
- → HDPE Reducer
End Cap
- Closes a pipe terminus. Used at temporary terminations during phased construction and at permanent dead-ends in distribution networks. Butt-fusion, electrofusion or threaded versions available.
Stub End
- Short HDPE fitting butt-fused or electrofused to a pipe end, designed to mate with a loose backing ring for flanged connections. The stub-end + backing ring + flange + gasket combination is the standard interface between HDPE and steel valves / pumps.
- → HDPE Stub Ends & Flanges
Saddle Fitting
- Branch tap installed onto an existing main without shutting it down: the saddle is electrofused / mechanically clamped to the pipe wall, a cutter then bores into the main to open the branch. Used for service-line connections to water and gas distribution.
Compression Fitting
- Mechanical pipe joining method using a rubber O-ring and a threaded compression nut. Common for DN ≤ 110 mm HDPE service lines and irrigation — no welder, no power, no skill barrier. Repairable in the field by any worker.
Trunk Main
- Large-diameter (typically DN ≥ 300 mm) transmission pipeline carrying treated water from a treatment plant to distribution-system reservoirs / pressure zones. HDPE's leak-proof fusion joints have made it the dominant material for new trunk mains since the 2000s.
Trace Wire
- An insulated copper wire laid above or alongside a buried plastic pipe so the pipeline can later be located by an electromagnetic detector. Standard practice for HDPE water and gas mains — required by most utility regulations.
Ductile Iron (DI)
- Cast iron alloyed with magnesium for ductility — historically the dominant material for water mains. Heavier, requires gasketed bell-and-spigot joints, susceptible to internal tuberculation and external corrosion. Increasingly displaced by HDPE for new installations.
- → HDPE vs Ductile Iron
Need a term we haven't covered? Email Primepoly Co., Ltd.'s engineering team at sales@primepolypipes.com.