"Rod" wrote in message
...

If I were to fit a full-bore valve (instead of the main stopcock), would I
need to add a check valve? (AIUI, some form of check valve is mandatory.
Or, as they say in Edinburgh, a meringue.)

Not mandatory. The shock goes into the mains when full bore. On high
pressure this can still cause thunks when taps are turned off, so a larger
whole house shock arrestor after the maintap is needed.

Change to a full-bore maintap and see. If OK leave. If reoccurs fit a small
arrestor on the most offending tap. If all of them then one large arrestor
at the main tap, or kitchen tap, which is usually first on the line anyway,
and easily hidden under the sink and easy to get at.

Yes use both spelling if searching.