AHHH!!!  Copper drain pipes?  What a disaster waiting to happen.  And a 
mixing vat for all the chemicals that go down the drain?  Who thought that 
up?  It might work for industry with one or two chemicals, but in a histo 
lab, the wide variety of chemicals will be a nightmare.  Imagine what the 
disposal of the marble chips and the sludge that will eventually coat it.  
You will need to know every chemical ever dumped so that the disposal can be 
performed properly.  All laboratories that I have ever seen have had plastic 
pipes (although I will admit my experience is limited) and they have worked 
perfectly fine.  Eventually the marble chips will not neutralize acids 
efficiently, and when the acid hits those copper pipes...  Well lets just 
say, that I would not want to be one story below you.  :-(

My Opinion,
Ron Bell, DVM, DACVP