How to Choose the Right PPR Pipe Size for Your Project

Why Getting PPR Pipe Size Right Matters

A plumber recently replaced all the pipes in a three-storey building. The hot water pressure on the top floor was weak — barely enough for a shower. The diagnosis? Undersized main supply lines. The entire system had to be partially redone.

Choosing the wrong PPR pipe size doesn’t just reduce flow. It can cause pressure drop across your whole system, lead to noisy pipes from high-velocity water, and accelerate wear on fittings and valves.

PPR pipes are used in a wide range of applications — from small home plumbing to large commercial systems. Before we talk sizes, if you’re new to PPR, start with our post on what are PPR pipes and fittings and why PPR pipe is used.

Key Facts About PPR Pipe Sizing

• PPR pipe sizes are measured by outer diameter (OD) in millimeters
• Common residential sizes: 20mm, 25mm, 32mm
• Common commercial/main line sizes: 40mm, 50mm, 63mm, 75mm, 90mm, 110mm
• Wall thickness depends on the pressure class (PN10, PN16, PN20, PN25)
• Smaller ID = more pressure drop; always size up for long runs

What Do PPR Pipe Size Numbers Mean?

When you see a PPR pipe labeled as “25mm PN16”, here’s what it means:

Outer Diameter (OD)

The size number (e.g., 20mm, 32mm, 63mm) refers to the outside diameter of the pipe. This is the standard measurement used across the industry. The internal diameter (ID) — which controls how much water flows — depends on the wall thickness, which is set by the pressure class.

Pressure Nominal (PN) Rating

PN stands for Pressure Nominal — the maximum pressure the pipe handles at 20°C. Higher PN = thicker walls = smaller internal bore for the same OD. Learn more in our guide on the difference between PN10 and PN16.

• PN10: 10 bar working pressure
• PN16: 16 bar working pressure
• PN20: 20 bar working pressure
• PN25: 25 bar working pressure

For most residential hot water applications, PN20 is the standard. For cold water supply, PN16 is commonly used. See our post on is PPR pipe compatible with hot or cold water for more details.

Standard PPR Pipe Sizes Available

PPR pipes are manufactured in standard sizes following ISO and DIN standards. Here are the most common sizes and their typical applications:

Size (OD)	Typical Use	Flow Rate (approx.)	Common PN Rating
20mm	Individual taps, showers	Low (1–2 fixtures)	PN20
25mm	Branch lines, small bathrooms	2–4 fixtures	PN16 / PN20
32mm	Sub-mains, small floor distribution	4–6 fixtures	PN16 / PN20
40mm	Floor mains in buildings	6–10 fixtures	PN16
50mm	Riser pipes, medium commercial	10–20 fixtures	PN16
63mm	Building main supply	20–40 fixtures	PN10 / PN16
75mm	Large commercial buildings	40–70 fixtures	PN10 / PN16
90mm	Main risers, apartment blocks	70–120 fixtures	PN10
110mm	Large industrial / municipal	120+ fixtures	PN10

For specific size availability, browse our high pressure pipe fittings by size or our full PPR pipes and fittings supplier page.

How to Choose the Right PPR Pipe Size

Here’s a simple step-by-step approach that works for most residential and light commercial projects:

Step 1: Count Your Fixtures

Start by listing all the fixtures connected to the line — taps, showers, washing machines, water heaters, etc. Each fixture has a demand flow rate. The more fixtures on a line, the larger the pipe you need.

Step 2: Calculate the Total Demand

Add up the peak demand flow rate for your fixtures. For residential buildings in the UAE, a common rule of thumb is to use 25mm for branch lines serving 1–4 fixtures and 32mm for sub-mains serving up to 6.

Step 3: Check the Pipe Run Length

Longer pipe runs increase friction and reduce pressure. For runs over 20–30 metres, size up by one step to compensate for friction losses.

Step 4: Consider Water Pressure at Source

If your supply pressure is low, undersized pipes make it worse. See our guide on how to increase water pressure in a pipe for practical solutions.

Step 5: Choose the Right PN Rating for Temperature

For hot water systems, use PN20 or PN25. For cold water, PN16 is typically sufficient. Higher temperature reduces the working pressure of PPR, so a higher PN rating compensates for this.

Also helpful: our guide on how to measure pipe size if you need to match existing pipes in a retrofit project.

PPR Pipe Size by Application

Residential Single Home (Villa)

• Main entry line: 32mm or 40mm
• Bathroom branch lines: 20mm–25mm
• Kitchen supply: 20mm–25mm
• Water heater feed: 25mm–32mm

Mid-Rise Apartment Building (5–10 Floors)

• Main riser: 63mm–90mm
• Floor distribution: 40mm–50mm
• Individual flat/unit branch: 25mm–32mm

Commercial Building (Hotels, Offices)

• Main supply: 90mm–110mm
• Floor mains: 50mm–63mm
• Individual zone branches: 32mm–40mm

For all fittings to match your chosen sizes, see our PPR pipe fitting types guide and our pipes and fittings supplier page in Dubai.

Pressure Rating and Size: What You Need to Know

Here’s something most people miss: the PN rating affects the internal bore of the pipe. Two 32mm PPR pipes with different PN ratings will have different internal diameters.

Pipe OD	PN Rating	Wall Thickness	Internal Diameter
32mm	PN10	2.9mm	26.2mm
32mm	PN16	4.4mm	23.2mm
32mm	PN20	5.4mm	21.2mm
32mm	PN25	6.7mm	18.6mm

A PN25 pipe of 32mm has roughly 30% less internal area than a PN10 pipe of the same size. For hot water systems, always account for this when calculating flow requirements.

For a deeper look at SDR ratios (which define wall thickness), read our SDR 11 vs SDR 17 comparison.

PPR Pipe Size Selection: Common Mistakes

1. Using the Same Size for Mains and Branches

Your main line should always be larger than your branch lines. Using 20mm throughout — from the header to every fixture — is a very common mistake in small buildings, and it kills pressure everywhere on the system.

2. Ignoring Thermal Expansion

PPR expands more than metal under heat. Long hot water runs need expansion loops or offsets. Our guide on how to connect PPR pipes covers this in detail.

3. Not Accounting for Fittings

Each fitting (elbow, tee, reducer) adds resistance equivalent to extra pipe length. Add 20–30% to your calculated pipe length when working out sizing to account for fitting losses.

4. Buying by Price, Not Quality

Low-quality PPR can have inconsistent wall thickness that fails under pressure. Know how to check PVC pipe quality — the same visual checks apply to PPR. Always buy from a trusted pipes supplier in Dubai.

5. Skipping Pressure Testing

After installation, always pressure test your PPR system before closing walls or burying pipes. Read our guide on how to pressure test PVC pipe — the process is similar for PPR systems.

Frequently Asked Questions

Get the Right PPR Pipe for Your Project

Choosing the right PPR pipe size comes down to three things: how many fixtures you’re serving, how far the water needs to travel, and what temperature and pressure the system will run at.

Use the guidelines in this article as your starting point. For larger or more complex projects, always consult with a qualified plumber or pipe supplier who can review your full system design.

Need Help Choosing the Right PPR Pipe Size? Contact Dave Pools in Dubai

Explore our full PPR pipes and fittings range, our products page, or learn more about us on our about page.