GRP Pipe Sizes Guide: From Small DN to Large-Scale Pipelines

From rural piping systems to large-scale industrial pipelines, GRP pipes include an adaptable design for various applications like water supply, sewage systems, and chemical pipelines. But what exactly shapes this potential? The right GRP pipe sizes, dimensions, and specifications provide a wide range of remarkable components, followed by global standards.

This guide represents the properties of GRP pipes that influence the pipe size, including tables and charts for engineers and project managers to ease the process of pipe selection based on project demands.

Before we dive into the main sections, let’s clarify GRP pipe’s sizes at a glance in the table below:

Aspect	Key Details
Diameters (DN)	50–300 (small), 300–1000 (medium), 1000–4200+ (large)
Lengths	Standard: 6m, 12m; Jacking: 1–6m; Custom: up to 15m
PN Classes	1–40; Higher = thicker walls for pressure
SN Classes	2500–20000+; Up to 1M for jacking; Matches burial/load
Standards/Apps	AWWA M45, ASTM D2996; For water/sewage/industrial—DN for flow, SN for depth

GRP Pipe Diameter (DN) Ranges

Diameter sizes are known as the central part of GRP pipes. These pipes provide a wide range of diameters for tiny irrigation networks to large-scale industrial piping systems like oil and gas pipelines.

Standard Nominal Diameters

Nominal diameters (DN) of GRP pipes can range from 50 mm to 4000 mm or more, depending on the manufacturer. This property eases the process of GRP pipe selection in every piping project based on their demands, followed by standards and guidelines.

For instance, as Amiblu highlighted that larger ones over DN 3000 are designed for heavy and high-pressure transmission in desalination plants or sewers, while smaller ones, like DN 50 to 100, handle low-flow systems.

How Are GRP Pipes Classified By DN?

GRP pipes are mainly divided into three categories: small (DN 50–300 mm) pipes for small-scale industrial or residential use; medium (DN 300–1000 mm) pipes for municipal water and sewage; and large (DN 1000–4000+ mm) pipes for major infrastructure.

• Pro Tip: Installation techniques vary depending on the class; for example, small ones may use hand laying, while larger ones may use heavy machinery like cranes.

Consistent OD Across Pressure Classes

GRP has the advantage that, regardless of the pressure class (PN), the outside diameter (OD) remains constant for a given DN. Wall thickness adapts to increased pressures, but fittings can be switched out with ease without requiring a complete calibration due to the OD consistency.

GRP Pipe Outer Diameter (OD) Tolerances

Outer diameters show how pipes are designed for reliable and long-lasting fittings and connections with no leak or failure included. Here’s a table for how DN and OD are adapted together per ASTM D3567 via processes like filament winding across batches to shape tight and consistent pipes.

Nominal Diameter (DN mm)	OD Tolerance (mm)
50–150	±1.0–1.5
200–300	±1.5–2.0
400–600	±2.0–3.0
800–1000	±3.0–4.0
1200–2000	±4.0–5.0
2500–4200+	±5.0–6.0

Importance of Fittings and Jointing Compatibility

In trenchless or jacking setups, even a 2 mm mismatch can result in joint failure, so standards like AWWA M45 are necessary for reliable connections. Correct OD tolerances ensure elbows, tees, and flanges align specifically for adhesive or rubber seal joints.

GRP Pipe Length Options

GRP pipes, unlike their alternatives, such as steel or ductile iron pipes, are more adaptable in length for transportation and installation sections due to their lightweight and various jointing methods.

Standard Manufacturing Lengths

GRP pipes are normally designed in 6m to 12m lengths, which are perfectly suited for most projects like water and wastewater systems. (Source: Scribd) Manufacturers make pipes in these sizes to balance the transport, jointing, and installation to reduce the time and cost.

Short Lengths for Trenchless Projects

In trenchless or jacking projects that require shorter lengths like 1-6m to control the movement in tight areas and underground installations without compromising the strength or performance over decades.

Custom Long Lengths for Special Projects

Manufacturers provide custom lengths up to 15 meters for projects that need long-distance pipelines to decrease the joint requirement and installation time in open-trench installations.

DN (mm)	Standard Lengths (m)	Jacking Lengths (m)	Custom Lengths (m)
300	6, 12	1–6	Up to 15
1000	6, 12	2–6	Up to 15

GRP Pipe Pressure Classes (PN)

GRP pipes are reliable options for high-pressure systems due to their adaptive pressure classes and wall thickness to handle internal pressure in water, sewer, and chemical pipelines.

Below, a comparison table represents the PN levels based on the DN and the offered wall thickness in further installations.

Nominal Diameter (DN mm)	PN Level (Bars)	Approx. Wall Thickness (mm)
300	6	6–8
300	16	8–10
600	10	8–10
600	25	12–15
1000	6	10–12
1000	20	15–18

• Additional Tip: The higher PN classes get, the thicker the walls are designed to tolerate specific pressures. For instance, for a DN 600 pipe, PN 6 might need 8 mm walls, while PN 25 requires 12–15 mm. (Source: Amiblu)

GRP Pipe Stiffness Classes (SN)

GRP pipes, with their high stiffness classes compared to the alternatives, resist external loads and heavy traffic or soils in harsh conditions and complicated installations. Here’s how SN classes of GRP pipe affect their sizes.

Standard SN Classes

GRP pipes are typically manufactured in 2500, 5000, 10000, and 20000 N/m² of SN classes, per AWWA M45, where lower ones are used in shallow burials and irrigation networks that are above the ground, and higher ones are installed in deeper or high-traffic areas like highways.

High SN for Jacking Pipes

In trenchless or jacking projects that require higher SN classes up to 1,000,000 N/m², GRP pipes can be produced to resist extreme pressures in urban piping systems or river crossings.

How SN, DN, and Burial Depth Are Related?!

Larger pipe diameters (e.g., DN 1000+) with high SN require thicker walls to maintain rigidity, especially in deep burials (10m+). Smaller DN sizes with lower SN work for shallow trenches..

DN (mm)	SN Class	Burial Depth (m)
300	5000	1–3
1000	10000	3–6

Consider matching SN classes to burial depth to shape a long-term performance over decades with reduced maintenance requirements.

Wall Thickness Correlation

After inspecting GRP pipe properties and how they affect their sizes, this section determines wall thickness and its impact on cost, weight, and resistance of GRP pipes in high-pressure systems.

How DN, PN, and SN Together Indicate Wall Thickness

The right combination of DN, PN, and SN creates such a stable wall thickness across various applications. Consider the larger DN gets, the thicker walls are.

• According to the AWWA M45, higher PN adds layers for internal loads, and higher SN increases resistance against external loads with no deflection or deformation included.

Below is a table to give engineers ideas on how these components change the wall thickness:

DN (mm)	PN	SN	Thickness (mm)
300	6	2500	4.20
300	16	5000	5.10
600	10	10000	11.20
1000	6	2500	11.24
1000	20	10000	17.50

Fittings and Dimensional Consistency

GRP pipe fittings are produced to match pipe DN sizes more easily for a leak-proof water or sewage system that requires standardized elbows or tees.

• Fitting Sizes and DN: Flanges, tees, and elbows are all designed exactly with DN ranges of 50 to 4200 mm. According to AWWA M45, elbows are available in 45°, 60°, and 90° angles; tees are available in equal or reducing types; and flanges are available in fixed or loose ring styles.

Size Table and Charts

For GRP pipe specs, clear size tables and charts make pipe selection easier for engineers and contractors. They show DN against OD with tolerances, wall thickness changes for different PN and SN ratings, and standard lengths for each DN.

Here are two tables, one for DN and OD and how they affect tolerance, and another one to show how DN, PN, and SN can change the game for wall thickness.

GRP Pipe Diameter (DN)(mm)	GRP Pipe Outer Diameter OD (mm)	Tolerance +/- (mm)
200	207	+1.0 / -1.0
300	310	+1.0 / -1.0
350	361	+1.0 / -1.2
400	412	+1.0 / -1.4
450	463	+1.0 / -1.6
500	514	+1.0 / -1.8
600	616	+1.0 / -2.0
700	718	+1.0 / -2.2
800	820	+1.0 / -2.4
900	924	+1.0 / -2.6
1000	1026	+2.0 / -2.6
1100	1128	+2.0 / -2.6
1200	1229	+2.0 / -2.6
1300	1330	+2.0 / -2.6

• For DN 200–300, OD tolerances tighten to ±1.0 mm, which contains such a specific alignment for fittings and connections.

GRP Pipe Diameter (DN)(mm)	Wall Thickness PN 6 (mm)	Wall Thickness PN 10 (mm)	Wall Thickness PN 16 (mm)	Wall Thickness PN 20 (mm)	Wall Thickness PN 25 (mm)	Wall Thickness PN 32 (mm)
200	3.00	3.00	3.00	3.00	3.00	3.28
300	3.72	3.72	3.69	3.65	3.65	4.31
350	4.23	4.21	4.12	4.09	4.10	4.83
400	4.73	4.72	4.59	4.56	4.53	5.35
450	5.30	5.18	5.02	4.99	4.97	5.87
500	5.86	5.66	5.48	5.43	5.42	6.41
600	7.05	6.62	6.40	6.33	6.35	7.45
700	8.16	7.53	7.26	7.22	7.21	8.49
800	5.61	8.50	8.18	8.11	8.06	9.58
900	10.23	9.41	9.05	8.96	8.97	10.61
1000	11.24	10.38	9.95	9.85	9.84	10.75
1100	12.24	11.22	10.82	10.74	10.69	12.69
1200	13.28	12.17	11.73	11.57	11.56	13.73
1300	–	–	–	–	–	–

• To increase the pressure resistance in GRP pipes, manufacturers design pipes for DN 300 at PN 32 that require 4.31 mm thickness for SN 2500.

Final Thought

GRP pipe sizes are all about the specific components, such as nominal diameter, pressure classes, stiffness classes, and wall thickness, that can match project demands. Consistency in outer diameters in various lengths creates a wide range of options across many applications, from tiny irrigation plants to large-scale oil and gas pipelines that require specific characteristics. Via tables and charts, engineers and contractors select the right pipe for long-term performance.

FAQs

1- What is the relationship between SN, DN, and burial depth?

Larger DN with high SN is needed for deep burials, while smaller DN with lower SN suits shallow trenches.

2- What is the DN range for GRP pipes?

Nominal diameters (DN) of GRP pipes can range from 50 mm to 4000 mm or more, depending on the manufacturer.

3- How are GRP pipes classified by DN?

Small (DN 50–300 mm) for small-scale use, medium (DN 300–1000 mm) for municipal systems, and large (DN 1000–4000+ mm) for major infrastructure