On Sat, 07 Dec 2013 23:07:22 +0000, Colin Stamp wrote:

Now though I've got round to re-doing it "properly", which consisted of
installing an appliance standpipe directly underneath the boiler drain.
This has the side effect that the boiler now makes a piddling noise
which can be heard in the room above.

Presumably the stand pipe has a trap and you can hear the condensate
dropping from the boiler drain into the water in the trap? If so just
arrange for the condensate to flow down the side of the stand pipe.
Maybe cut the end of the drain pipe at an angle and place the point
against the side of the standpipe.

--
Cheers
Dave.