PPR Pipe Sizes: Selection Guide for Saudi Construction Projects

Selecting the correct PPR pipe sizes is one of the most practical decisions in plumbing design. An undersized pipe causes weak pressure, noise, and premature wear, while an oversized one wastes budget and can leave hot water standing in the line. The purpose of this guide is to explain how PPR pipe sizes are defined, what each diameter is typically used for, and how to choose the right size for villas, apartment towers and commercial buildings across Saudi Arabia. It is written for engineers, contractors and procurement teams who want clear, usable guidance before finalising a specification.

How PPR Pipe Sizes Are Measured

PPR pipes are sized by their outside diameter (OD) in millimetres, not by internal bore as many steel pipes are. Common sizes run from 20 mm up to 110 mm, with larger diameters available for main lines. A 25 mm pipe therefore has an outside diameter of 25 mm, but the actual internal diameter depends on wall thickness.

This distinction matters. Two 32 mm pipes from different pressure classes have the same outside diameter but different internal diameters, which changes flow capacity. A thicker-walled PN20 pipe has a smaller bore than a PN16 pipe of the same nominal size. For background on how wall thickness relates to pressure class, see our guide on PPR pipe pressure rating and temperature limits.

Many specifications still refer to inch sizes, so a rough conversion helps: 20 mm is about ½ inch, 25 mm about ¾ inch, 32 mm about 1 inch, 40 mm about 1¼ inch, 50 mm about 1½ inch, 63 mm about 2 inch and 110 mm about 4 inch. These are approximate equivalents, not exact matches.

PPR Pipe Sizes Chart and Typical Use

The table below shows common sizes with indicative internal diameters for PN20 (SDR 6) pipe, plus approximate flow at a design velocity of 1.5 m/s. Figures are rounded and vary slightly by manufacturer, so verify against certified datasheets.

Remember that these are capacity guides, not substitutes for a proper hydraulic calculation.

Factors That Determine the Right Size

Water demand

Start with how much water the system must deliver at peak. Designers typically assign fixture units to each outlet, convert the total to a probable simultaneous flow, and then size each pipe section for the flow it carries. Requirements for plumbing design in the Kingdom are set out in the Saudi Building Code, so check the provisions that apply to your building type.

Design velocity

Water velocity is the practical limit on pipe size. Most designers aim for roughly 1 to 2 m/s. Higher velocities increase noise, pressure loss, and the risk of water hammer, while very low velocities can encourage stagnation, particularly on hot water lines. Hot water and recirculation loops are often sized conservatively, at the lower end of this range.

Pressure loss

Smaller pipes lose more pressure per metre. In a tall building, friction losses combine with static head, and a pipe that works fine on the ground floor may starve the top floors. Smooth PPR walls help keep friction lower than metal alternatives, but losses through fittings, valves and bends still add up and must be included.

Pressure class

Because wall thickness changes the internal diameter, pressure class and pipe size must be chosen together. Selecting a higher class for a hot or high-rise system leaves a smaller bore, so you may need to step up one nominal size to maintain flow. Higher-strength material can ease this trade-off, and our comparison of PPR vs PPR-CT explains how thinner walls can preserve internal diameter.

Sizing for Common Saudi Project Types

Villas and low-rise housing. Branches are commonly 20 and 25 mm, with 32 to 50 mm mains depending on the number of bathrooms and kitchens. Roof tank feeds often need 40 to 50 mm to keep flow reasonable during peak morning use.

Apartment towers. Risers typically range from 63 to 110 mm, tapering as they ascend and supply fewer floors. Branches into each unit often start at 32 mm and reduce to 25 and 20 mm at fixtures. Higher pressure at lower floors may call for a higher pressure class or pressure-reducing valves.

Hotels and commercial buildings. These have high simultaneous demand and long hot water recirculation loops. Larger mains and carefully balanced loops are common, and material choice matters. Our guide to PPR-CT pipes for solar water heating systems is relevant where solar or centralised heating is used.

Climate Considerations in Saudi Arabia

High ambient temperatures affect size selection in subtle ways. Rooftop tanks and exposed lines warm the water, which reduces the pipe’s pressure capacity, and hot lines expand noticeably, requiring room for expansion loops and supports. For a broader view of how the material copes with heat, read PPR pipe vs CPVC in Saudi Arabia. Expansion control is covered in detail in the article on thermal expansion in centralized hot water loops, and its principles apply equally to projects in the Kingdom.

Matching Fittings to Pipe Size

A system is only as reliable as its connections. Fittings must match the pipe’s size and pressure class, and reducers should be used thoughtfully, since abrupt changes in diameter add turbulence and pressure loss. Browse the available PPR fittings when preparing your bill of quantities. Installation quality matters just as much: incorrect fusion times are a leading cause of leaks, as explained in common PPR fitting installation mistakes in Saudi Arabia.

Common Sizing Mistakes to Avoid

• Sizing only by outside diameter. Always check the actual bore for the chosen pressure class.
• Ignoring peak demand. Systems designed for average use often disappoint at peak times.
• Oversizing hot water lines. Excess volume wastes water and energy while waiting for hot water.
• Forgetting future expansion. Allow reasonable capacity for added floors or fixtures where growth is likely.
• Skipping certification checks. Confirm that products meet SASO requirements and recognised standards.

Choosing a Reliable Supplier

Even a perfectly calculated size fails if the pipe’s actual dimensions are inconsistent. Look for suppliers with controlled wall thickness and documented testing, and review the quality assurance process behind the product. To understand what separates strong suppliers, read about top PPR pipe manufacturers and brands trusted across Saudi Arabia. You can also see how production works at a PPR pipes manufacturer, view the full PPR pipes range, explore PPR-CT pipes, and browse the AquaTerra brand.

Frequently Asked Questions

What are the standard PPR pipe sizes available?

Common sizes are 20, 25, 32, 40, 50, 63, 75, 90, and 110 mm outside diameter, with larger sizes available for main lines. Exact availability depends on the manufacturer.

Are PPR pipe sizes measured by inside or outside diameter?

They are measured by outside diameter in millimetres. The internal diameter depends on wall thickness, which varies with pressure class.

Which PPR pipe size is used for a typical bathroom?

Fixture connections usually use 20 mm, while the bathroom branch feeding several fixtures often uses 25 mm, subject to hydraulic calculation.

What water velocity should I design for in PPR pipes?

Most designs target about 1 to 2 m/s, using lower values for hot water and recirculation lines to limit noise, pressure loss and water hammer.

Does a higher pressure class change the pipe size?

The outside diameter stays the same, but the wall becomes thicker and the internal bore smaller, which reduces flow. You may need a larger nominal size to compensate.

Conclusion

Good PPR pipe size selection balances demand, velocity, pressure loss, and pressure class, rather than relying on rules of thumb. Calculate the flow, check the real internal diameter, size for the climate, and match your fittings to the pipe. A little care at the design stage prevents costly problems on site.

Need help sizing your project? Contact the Aquagas team for technical guidance and a quotation.