I have read about 15 pages of responses and didn't see my questioned answered. Before I ask my question I want to say thanks to all of you who answer all of these questions. I have learned a lot this evening! What a service you are providing.
Okay. I have a hair salon. The sink or bowl that I use to wash hair in has developed a leak in the strainer flange. It is not a leak at a joint. The short piece that the flange tapers into has a small pitted hole in it. Can this hole be filled with a plumbers epoxy? Or does the whole flange need to be replaced (Please say no) The sink is cast iron and the flange is stainless steel and then from there it drains into PVC pipe. My husband hopes you say it can be filled, we will wait and hear what you all have to say. Thanks.
Marla

You probably could epoxy it up but it wouldn't last very long. Another leak will soon pop up in another place since the metal has, shall we say, wasted away and gotten very thin. If you are speaking of the piece that I am thinking of its called the sink tail pipe. Its probably chrome plated brass and not stainless steal. Cheap and easily to replace.
If you have a "pop up" drain plug you may have to purchase a complete drain assembly. Still inexpensive and easily replaced. Loosen compression nut on PVC trap, unscrew tail pipe from sink flange and replace. If it looks more complicated than that or you think you need to replace entire drain assembly post a picture for instructions.

I think HK said it real well... If the flanged tailpiece is pitted, not long before it all goes. It is usually a quick fix... usually! See if these pics. Help. The exploded view of strainer assembly does not show that PUTTY needs to go between drain body and sink itself.. ok? The tailpiece in exploded view again, is flanged on one end (mates to strainer bottom with a strainer washer)... so is the chrome tailpiece in the right picture.

The few hair salon sinks I have installed had varied strainer assemblies... but most were just like kitchen sink strainers. If strainer at sink good... no need to replace now... but if any question as to its condition, replace it now.. should not be too hard as you can see.

If you do replace with a new kitchen sink strainer choose the type with the smaller locknut and basket(see pic. on right) ... NOT the type with large locknut (as in my exploded view picture below)... the larger nut type is NOT easy to work with.

Like Harold said, get back to us with more information.. then we can best advise you... right now we are just guessing for you.. ;)

Talk later... Mark

After hearing what you have said so far, my husband says he will just replace the whole strainer flange and tailpiece that all runs into the PVC pipe. (he may have to call the plumber in) He says the flange itself looks like it is rusting out in a few spots and will need to be replaced soon so he will just replace the entire section or have it done by professional. It is in an awkward area that is hard to get to and he has MS and was hoping epoxy would do the trick, that would make it easy on him. Thanks for your help!
Marla

It is the drain body that appears to be rusting out.

Would you like us to walk Hubby through the repair? Cheers, Tom