I can hear water running in the drain in the basement even though
there are no obvious leaks so I placed my hand above 'drain cover'?
(is that what you called the 6 inch diameter metal cover with holes in
it so that if the basement floods water will go away thru that?) and I
can feel its warm water thats leaking.

So I l ifted the 'drain cover'and discovered that there is a half inch
diameter plastic pipe embedded in the concrete and the hot water is
dripping into the drain from this pipe. But where is this pipe getting
this hot water from?

When I shut off the cold water supply to the (natural gas) water tank
(there is no tap to control the hot water existing the water tank) the
leak stops.

Any ideas, suggestions on where this leak originate from and how to
fix it?