What are the standard copper pipe sizes used in UK plumbing?

The most common copper pipe sizes in UK domestic plumbing are: 8 mm (micro-bore heating), 10 mm (micro-bore heating), 15 mm (hot and cold water, radiator tails), 22 mm (hot and cold mains, heating flow/return), 28 mm (main heating flow/return, large systems), 35 mm (commercial, large domestic), 42 mm (commercial), and 54 mm (commercial mains). 15 mm and 22 mm account for the vast majority of domestic plumbing work.

What is the difference between pushfit and solvent weld plastic pipe?

Pushfit pipe (e.g., JG Speedfit, Hep2O) uses rubber O-ring seals and can be connected without tools, glue, or heat. It comes in 10, 15, 22, and 28 mm sizes matching copper. Solvent weld pipe (PVC-U) uses a chemical cement to permanently bond joints. It is available in 19.05 mm (3/4"), 21.5 mm (3/4" waste), 32 mm (1.25" waste), 40 mm (1.5" waste), and 50 mm (2" waste) sizes. Pushfit is preferred for speed; solvent weld for permanence.

What size pipe do I need for mains water?

The standard service pipe from the water main to a UK domestic property is 25 mm blue MDPE (medium-density polyethylene). Inside the property, the mains cold feed is typically 15 mm or 22 mm copper or plastic. For properties with a combi boiler, a 22 mm cold main ensures adequate flow rate. The supply pipe from the boundary stopcock to the property must be at least 25 mm.

What are the standard waste pipe sizes in the UK?

Standard UK waste pipe sizes are: 21.5 mm (overflow pipes), 32 mm (basin waste), 40 mm (bath, shower, kitchen sink waste), 50 mm (commercial sinks, urinals), and 110 mm (soil pipe, WC connection). These are outside diameter measurements. Waste pipes should be installed with the correct fall gradient: 18-90 mm/m for 32 mm, 18-45 mm/m for 40 mm pipes.

Is plastic pipe suitable for heating systems?

Yes, barrier-type plastic pipe (PEX, PB, or MLCP with an oxygen barrier layer) is approved for central heating systems in the UK. Popular brands include JG Speedfit Barrier Pipe and Hep2O. The oxygen barrier prevents dissolved oxygen entering the system and corroding radiators and boiler heat exchangers. Standard non-barrier plastic pipe must NOT be used for heating as it is permeable to oxygen.

UK Pipe Sizes Reference — Free Trade Calculator

UK Pipe Sizes — Copper, Plastic and Steel Reference

Standard UK plumbing pipe sizes for copper, plastic (PVC, MDPE, PEX), and steel including outside diameters, wall thicknesses, and typical applications.

Copper Pipe Sizes (BS EN 1057)

OD (mm)	Wall (mm)	ID (mm)	Typical Use
8	0.6	6.8	Micro-bore heating
10	0.6	8.8	Micro-bore heating, gas pilot
15	0.7	13.6	Hot/cold water, radiator tails, gas
22	0.9	20.2	Hot/cold mains, heating flow/return
28	0.9	26.2	Main heating flow/return, gas
35	1.2	32.6	Commercial heating, large domestic
42	1.2	39.6	Commercial heating and water
54	1.2	51.6	Commercial mains, large systems

Plastic Pushfit Pipe Sizes

Size (mm)	Copper Equivalent	Colour	Typical Use
10	10 mm copper	White	Micro-bore heating
15	15 mm copper	White/grey	Hot and cold water, radiator tails
22	22 mm copper	White/grey	Hot and cold mains, heating
28	28 mm copper	White/grey	Main heating flow/return

Waste Pipe Sizes

OD (mm)	Imperial	Typical Use	Min Fall (mm/m)
21.5	3/4"	Overflow, condensate	-
32	1.25"	Basin waste	18
40	1.5"	Bath, shower, kitchen sink	18
50	2"	Commercial sinks, urinals	18
110	4"	Soil pipe, WC connection	18

MDPE Water Supply Pipe

OD (mm)	Colour	Typical Use
20	Blue	Small service connections
25	Blue	Standard domestic service pipe
32	Blue	Larger domestic, small commercial
63	Blue	Distribution mains

Related Calculators

Use the Pipe Sizing Calculator to determine correct pipe sizes, or the Radiator Pipe Calculator for heating pipe sizing. The Drainage Fall Calculator helps with waste pipe gradients.

How We Calculate This

Frequently Asked Questions

Last updated: March 2026

All calculations are estimates. Verify with your supplier.

UK Pipe Sizes — Copper, Plastic and Steel Reference

Copper Pipe Sizes (BS EN 1057)

Plastic Pushfit Pipe Sizes

Waste Pipe Sizes

MDPE Water Supply Pipe

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How We Calculate This

Frequently Asked Questions

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