Metric, imperial,

[Alan51]

Got an old stone house, other than getting a micrometer what clues give away metric or Imperial pipe. The copper looks really clean but it's been under the floor so that might mean nothing.
House is like an onion, I really need to stop peeling, pulled a load of lead pipe or so at least I'll get something back for that.
Also would a 15mm pushfit stop end work on 1/2 inch whilst I get new pipe in ready to swap over. Thanks

 

[Stivino]

Sometimes the solder ring fittings and the pipe have the size stamped on them so, have a good look first if you're not sure.

 

[ianmcd]

The pipes in your pic are metric