To identify your PVC pipe size, measure the outside diameter of a straight section, then check the pipe markings and sizing system. Metric PVC-U pressure pipe is sized by outside diameter: 50mm pipe measures approximately 50mm across. Imperial pipe uses nominal inch sizes: 2 inch PVC pressure pipe measures approximately 60.3mm outside diameter.
Use this guide to narrow down your pipe size before buying a replacement length, socket or adaptor. The charts cover PVC-U pressure pipe; household waste pipe and threaded connections need separate identification.
How do I measure my PVC pipe?
- Read the markings. Look for PVC-U or uPVC, the manufacturer, size, pressure class and standard. Photograph any readable printing.
- Choose a straight section. Measure the pipe itself, away from a socket, flared end, thread or damaged area.
- Measure across the outside. Use the external jaws of callipers, keeping them square to the pipe. Record the measurement in millimetres.
- Check a second direction. Measure again at a right angle to the first reading. Different readings may indicate distortion or an inaccurate measurement.
- Match the measurement and markings. Use the charts below to identify a likely size, then confirm the manufacturer's specification before ordering.
Do not cut or disconnect a working system just to measure it. An accessible straight section is enough to measure the outside diameter.
Can I measure pipe size without callipers?
You can estimate the outside diameter by measuring the circumference. Wrap a narrow paper strip around the pipe, mark where it overlaps, then lay it flat and measure between the marks.
Outside diameter = circumference divided by 3.142. For example, a circumference of approximately 189.4mm gives an outside diameter of about 60.3mm, suggesting 2 inch imperial PVC pressure pipe.
This is a preliminary check. Use callipers and pipe markings when distinguishing closely spaced sizes, especially if the pipe is painted, rough or out of round.
What size is metric PVC pressure pipe?
The metric size identifies the pipe's outside diameter, not the opening through its centre.
| Pipe size | Outside diameter |
|---|---|
| 20mm | 20mm |
| 25mm | 25mm |
| 32mm | 32mm |
| 40mm | 40mm |
| 50mm | 50mm |
| 63mm | 63mm |
| 75mm | 75mm |
| 90mm | 90mm |
| 110mm | 110mm |
These are nominal outside diameters, subject to manufacturing tolerances. View our metric PVC pressure pipe in 2m lengths for product specifications and size options.
What size is imperial PVC pressure pipe?
Imperial PVC pressure pipe uses nominal inch sizes. Converting the inch label directly into millimetres will not give its outside diameter.
| Nominal pipe size | Approximate outside diameter |
|---|---|
| 1/2 inch | 21.4mm |
| 3/4 inch | 26.7mm |
| 1 inch | 33.6mm |
| 1 1/4 inch | 42.2mm |
| 1 1/2 inch | 48.3mm |
| 2 inch | 60.3mm |
| 3 inch | 88.9mm |
| 4 inch | 114.3mm |
These reference dimensions match the sizes shown in our imperial PVC pipe product table. Confirm the exact pipe specification; this chart is not a universal guide to every inch-labelled plastic pipe.
Is 2 inch PVC pipe the same as 50mm or 63mm?
No. The outside diameters are approximately 60.3mm for 2 inch imperial pressure pipe, 50mm for 50mm metric pressure pipe and 63mm for 63mm metric pressure pipe.
Similarly, 1 1/2 inch imperial pipe measures approximately 48.3mm outside diameter, so it is not the same size as 50mm metric pipe. Read our metric versus imperial PVC guide for more comparisons.
Should I measure the inside or outside diameter?
Measure the outside diameter when identifying plain-ended PVC pressure pipe for matching sockets. The internal bore depends on wall thickness, so two pipes with the same outside diameter can have different internal diameters.
Do not use the outside width of an elbow or socket body as the pipe diameter. If only a fitting is accessible, look for moulded size markings and photograph the connection.
Why does my 40mm pipe not fit a 40mm pressure fitting?
You may be comparing different pipe systems. A nominal 40mm household waste pipe is not necessarily 40mm outside diameter. Its dimensions depend on the waste system and jointing method.
Check whether the pipe is pressure pipe or waste pipe before selecting a connector. Our PVC pressure pipe versus waste pipe guide explains this distinction. Matching dimensions alone does not establish pressure suitability.
Can I use these charts to identify a threaded fitting?
No. These charts describe the outside of plain pipe, not thread diameters. For a threaded connection, identify the thread size, pitch, type and sealing arrangement.
Use our PVC threaded fitting size guide when measuring a male or female thread.
Which PVC fitting should I buy once I know the size?
- Joining matching metric pressure pipes: choose the correct size of metric PVC equal socket.
- Joining matching imperial pressure pipes: choose the correct size of imperial PVC equal socket.
- Connecting metric and imperial systems: check our metric x imperial adaptor, including its socket/spigot arrangement and any additional fittings required.
Confirm material compatibility, pressure and temperature limits, and the specified jointing method before assembly. Do not force mismatched components together or use extra solvent cement to compensate for an incorrect fit.
What if I still cannot identify my PVC pipe?
Email sales@t-mex.co.uk with the outside diameter, photographs of the markings and connection, and details of what the system carries. Include its working pressure and temperature if known. You can also call 01622 470047.
Once identified, explore our metric PVC pipe and imperial PVC pipe ranges to find the required size and length.