I have an outside toilet with the water main coming up through the concrete
floor, this is black plastic with an outside dia of about 3/4 of an inch, it
then goes on to the stop cock and then to a piece of copper pipe with a
compression fitting, but this leaks like mad!!!!!!! the compression fitting
on the out going side of the stop cock does not seem to be a proper
compression fitting, I think it has been bodged to fit, so what I would like
to know is if I remove the stop cock, what new stop cock can I fit which
will fit the old black plastic water main and allow me to use some 15mm
copper to the toilet??

Richard