Question 1

What is the difference between Table X and Table Y copper pipe?

Accepted Answer

Table X (previously Table X in BS 2871) is the thinner-walled standard pipe used for most domestic plumbing. Table Y has thicker walls for higher-pressure applications or where the pipe will be bent extensively. For typical domestic hot and cold water, central heating and gas installations, Table X is standard. Table Y is used where higher pressure ratings or additional protection against corrosion is needed.

Question 2

What copper pipe size do I need?

Accepted Answer

Standard domestic sizes: 15 mm for individual hot and cold taps, basins and radiator feeds; 22 mm for main cold water distribution, hot water cylinder connections and main heating flow/return; 28 mm for main cold water supply from the mains, boiler connections and larger heating circuits; 8 mm and 10 mm for micro-bore heating systems and individual radiator connections.

Question 3

Can I connect copper pipe to plastic pipe?

Accepted Answer

Yes, using push-fit fittings (e.g. JG Speedfit, Hep2O) that accept both copper and plastic pipe, or with purpose-made copper-to-plastic adaptors. When connecting to push-fit on copper pipe, ensure the pipe end is clean, round and free of burrs. Some push-fit systems require a pipe insert (liner) in the plastic pipe but not in the copper pipe.

Question 4

Is copper pipe being replaced by plastic?

Accepted Answer

Plastic pipe (push-fit, barrier pipe, PEX) is increasingly used for domestic plumbing due to speed of installation and lower cost. However, copper remains preferred for exposed pipework, boiler connections, gas installations (where copper is mandatory), and situations requiring UV resistance or higher temperature ratings. Many plumbers use a combination of both.

Nominal Size (mm)	Outside Diameter (mm)	Wall Thickness (mm)	Common Use
8	8.0	0.6	Micro-bore heating
10	10.0	0.6	Micro-bore heating, overflow pipes
15	15.0	0.7	Taps, basins, radiator connections
22	22.0	0.9	Hot/cold distribution, heating mains
28	28.0	0.9	Mains supply, boiler connections
35	35.0	1.2	Commercial heating, large domestic
42	42.0	1.2	Commercial installations
54	54.0	1.2	Large commercial, mains distribution

Nominal Size (mm)	Outside Diameter (mm)	Wall Thickness (mm)	Notes
15	15.0	1.0	Higher pressure, heavy bending
22	22.0	1.2	Higher pressure applications
28	28.0	1.2	Higher pressure, underground

Method	Sizes (mm)	Suitability
End-feed solder (capillary)	8–54	Permanent, cheapest fittings, neat joints
Solder ring (Yorkshire)	8–54	Permanent, pre-loaded solder, faster than end-feed
Compression	8–54	Demountable, no flame, slightly bulkier
Push-fit (Speedfit etc.)	10–28	Quick, demountable, no tools or flame
Press-fit (Viega, Conex)	15–54	Permanent, no flame, requires press tool

UK Copper Pipe Sizes — Table X & Y

Table X Copper Pipe (BS EN 1057 / R250)

Table Y Copper Pipe (Thick Wall)

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