PLUMBCRATE
UK copper pipe sizes explained: 15mm, 22mm and 28mm
UK domestic copper pipe is sized by its outside diameter in millimetres. Fittings are made to match that outside diameter, so a 15mm fitting fits 15mm pipe.
Common sizes and typical uses
- 15mm - the most common size. Typically used for branches to taps, radiators, toilets and most appliances.
- 22mm - typically used for main runs: the incoming main after the stop tap in many homes, boiler flow and return, hot water cylinder feeds and bath taps.
- 28mm - used on larger systems, longer heating primaries and commercial work.
- 8mm and 10mm - microbore heating pipe, found in some older systems.
Imperial pipe
Older homes may have imperial copper: 1/2" is close to 15mm and 3/4" is close to 22mm, but not identical. 1/2" pipe usually works with 15mm compression fittings; 3/4" generally needs an adaptor or a dedicated imperial-to-metric fitting.
Choosing fittings
- End-feed (solder) fittings - neat and low cost, need a blowtorch.
- Compression fittings - spanners only, can be undone.
- Press-fit fittings - flame-free and quick, need a press tool.
Use the size filter on any collection page to show only 15mm, 22mm or 28mm parts.