PPR Pipe Sizes: Selection Guide for UAE Plumbing Projects

Picking the wrong pipe diameter is one of the most common and costly mistakes in building services. An undersized line causes low pressure, noise, and fast wear, while an oversized one wastes budget and slows hot water delivery. The purpose of this blog is to explain PPR pipe sizes clearly, so contractors, consultants, and property owners in the UAE can read a size chart, understand dimensions, and choose the right diameter for each part of a plumbing system. You will learn how sizes are labelled, how wall thickness changes the real water capacity, and how to match a size to its job.

How PPR Pipe Sizes Are Measured

Unlike steel or copper pipes, PPR pipes are sold by their outside diameter (OD) in millimetres. A pipe labelled 25 mm has an outer diameter of 25 mm, regardless of how thick its wall is. This is different from the “nominal size” in inches that many people are used to, which is only a rough label.

The common PPR pipe diameters are 20, 25, 32, 40, 50, 63, 75, 90 and 110 mm, with larger sizes available for bigger networks. As a rough guide, 20 mm is close to the old 1/2″ or 3/4″ class, 25 mm to 1″, and 32 mm to 1 1/4″. For more background on how nominal sizing works in general, see this overview of nominal pipe size.

Because the outside diameter stays fixed, a thicker wall simply eats into the inside space. That brings us to the most important concept in sizing.

Why Wall Thickness Matters for Real Capacity

Water flows through the inner diameter, not the outer one. The inner diameter equals the outside diameter minus twice the wall thickness. Wall thickness depends on the pipe’s pressure class: a PN20 pipe has a thicker wall than a PN10 pipe of the same OD, so its bore is smaller.

For example, a 25 mm PN20 pipe has a wall of about 4.2 mm, leaving an inner diameter of roughly 16.6 mm. A 25 mm PN10 pipe has a wall of around 2.3 mm and an inner diameter near 20.4 mm. That is a noticeable difference in flow area, and it should be considered during design, not after installation.

If you want a refresher on how pressure classes and wall thickness relate, our team covers the basics of pressure and temperature ratings in the PN10, PN16 and PN20 guide.

PPR Pipe Size Chart (PN20 Example)

The table below shows typical dimensions for PN20 (SDR 6) pipes, the class most often used for hot and cold water. Values are approximate and may vary slightly by manufacturer, so always confirm against the product datasheet.

You can view the full available range on the PPR pipes product page.

How to Choose the Right Size Step by Step

1. Estimate the flow demand. Count the fixtures served (basins, showers, WCs, kitchen taps) and apply a recognised demand method to estimate peak flow. Not every fixture runs at once, so using the sum of all fixtures will lead to oversizing.
2. Set a target velocity. A common design range for water in plastic piping is roughly 0.5 to 2 m/s. Many engineers aim for about 1 to 1.5 m/s on hot water and recirculation lines to limit noise and erosion. Higher velocities raise pressure loss and can increase the risk of water hammer, which you can read about in this general explanation of water hammer.
3. Calculate the required inner diameter. Flow equals pipe cross-section area multiplied by velocity. As a quick example, a 25 mm PN20 pipe (inner diameter 16.6 mm) at 1.5 m/s carries about 0.32 litres per second, or roughly 1.2 cubic metres per hour. If your branch needs more than that, move up a size.
4. Check pressure loss. Long runs, many fittings and tall risers all add friction loss. Make sure the remaining pressure at the farthest outlet is still enough for the fixture to work properly.
5. Confirm the pressure class. Hot water systems generally use PN20, while cold lines may use a lower class. Matching the class to the temperature avoids both over-specification and early failure.

Sizing by Application

Hot and cold water branches: 20 and 25 mm cover most fixture connections inside apartments, villas and offices.

Apartment and villa mains: 32 to 50 mm typically serve a full unit or a small group of fixtures.

Risers and headers in high-rise buildings: 63 to 110 mm are common, and designers often check whether PP-RCT would allow a better balance of wall thickness and capacity. Our article on PPR-CT vs PPR pipes for high-rise projects explains this in detail, and you can also view the PPRCT pipe range.

Chilled water and heating lines: Sizing here depends on flow rate and temperature difference, and insulation should be planned alongside the diameter.

Common Sizing Mistakes to Avoid

Ignoring wall thickness. Designers who calculate flow using the outside diameter overestimate capacity, especially in PN20 pipes.

Oversizing “to be safe.” Larger pipes cost more, hold more standing water and take longer to deliver hot water, which wastes energy and water.

Forgetting thermal expansion. PPR expands with heat, roughly 0.15 mm per metre for each degree of temperature rise. A 10 m hot line heated by 50°C can grow around 75 mm, so expansion loops, offsets or proper supports are essential.

Mismatching fittings and pipes. Fittings must match the pipe’s OD and pressure class. Before choosing a joining method, read our comparison of compression vs fusion fittings and browse the PPR fittings available for each size.

Buying without checking quality. Dimensions only matter if the pipe actually meets them. Review the quality and certifications behind the product, understand how accuracy is controlled at the manufacturing facility, and use our list of questions on choosing a certified PPR pipe manufacturer when comparing suppliers. Pipes should follow recognised standards such as ISO 15874.

Frequently Asked Questions

1. What are the standard PPR pipe sizes?
   The most common outside diameters are 20, 25, 32, 40, 50, 63, 75, 90 and 110 mm. Larger diameters are available for bigger projects.
2. Are PPR pipe sizes measured by inside or outside diameter?
   PPR pipes are sold by outside diameter in millimetres. The inner diameter depends on the wall thickness of the chosen pressure class.
3. What size PPR pipe is used for a bathroom?
   Branches to individual fixtures usually use 20 mm, while a full bathroom group is often supplied by 25 mm. The final choice depends on the number of fixtures and flow demand.
4. Does a higher pressure class change the pipe size?
   The outside diameter stays the same, but the wall becomes thicker and the inner diameter smaller. This reduces flow capacity slightly for the same OD.
5. Can I use the same size for hot and cold water?
   Often yes, but hot water lines should use a suitable pressure class such as PN20, and the diameter should be checked against flow, velocity and heat loss.
6. What happens if the pipe is too small?
   You may get low water pressure at outlets, noisy flow, higher pressure drop and extra stress on the system. Proper sizing avoids these issues.

Conclusion

Choosing the right PPR pipe sizes comes down to understanding outside diameter, wall thickness and real flow needs. Start with expected demand, set a sensible velocity, check the inner diameter and pressure loss, and then match the pressure class to the temperature of the water. A careful sizing exercise at the design stage prevents expensive fixes later.

To learn more about the company behind these products, read the Aquagas company profile or about us, visit the Aquagas home page, or explore more articles on the UAE blog. For help selecting sizes or requesting a quote, contact the Aquagas team.