I recently acquired on eBay a 2 yrs old kitchen that will fit almost
perfectly into a property I am renovating for rental.

The sink is a dual bowl 'granite effect ' like this

http://www.taskersonline.com/product..._granite_sink/

Now the sink has no holes for overflows in either bowls ( no position
partially drilled either ) and I'm a bit concerned that careless tenants
could leave taps running whilst distracted elsewhere causing a flood in the
kitchen and resultant damage to kitchen units/flooring etc.

What solution would best suit the 'granite effect' sinks - should I drill
and fit a chrome overflow to each ( chrome would look a bit out of keeping
with the granite ) or are other options available and where from.

The basket strainers for each bowl were not included so I will be buying new
ones of those anyway.

ALSO - as an aside:

The property previously had a single bowl sink unit with one waste pipe to
the outside.

Do I need to provide two pipes to the outside or can the waste from each
bowl be combined into one waste pipe on the inside.

If on one pipe would there be a rise of waste water in the second bowl if
the 'plug' was removed from the first to drain that bowl.

Thanks in advance - Colin