Designing Kitchens and Bathrooms - Problems installing new tub drain

I am remodeling our bathroom and I replaced the old tub with a new American Standard Americast tub. I left the old plastic overflow and drain plumbing in place. The problem I am having is that the drain is leaking, no matter what I try. I've tried plumbers putty by itself, and plumbers putty with silicone on the top edge of the shoe lip, I've tightened it snug and I have tightened it to the point where I was afraid it would break the tub. There is a rubber washer that came with the drain kit, the instructions don't show where it goes but I assumed it went between the tub and drain pipe, so hopefully that part is right. For the life of me I can't figure out why it continues to leak. I can go in my basement and see that the water is running over the top of the rubber gasket... Any thing I haven't done right or any suggestions would be appreciated.

Is the old drain plumbing PVC pipe. Was your new drain assembly inside the tub threaded into the old drain plumbing?

Get back to me on that hook up so I can have a more clear picture of the drain hook up.

Duke of ....

Yes, you are right on both questions. I have considered buying a new pvc drain assembly and using the part that the has the threads. But I can't see how that would be the problem when the leak is seeping between the rubber gasket and the tub. But heck, I'll try ANYTHING to make this work.

I'm not sure I understand your description.

The rubber gaskets usually go underneath, usually (from the bottom up) there is the threaded drain fitting, rubber gasket, and then the tub. Above, the tub drain is set in place with only plumber's putty between the drain and the tub.

Here is a sample installation instruction that show a typical assembly. The parts are brass, but plastic drains are very similar.

http://www.us.kohler.com/onlinecatalog/pdf/1010455_2.pdf

Did you check the undersurface of the tub where it is bored for the drain hole? If it is uneven or marred the rubber gasket may not seal properly. The only plumbers putty that should be needed is on the undersurface of the strainer. The PVC unions should only require a poly washer.

I recently installed a Geberit BWO on a fiberglass tub. The installation instructions are highlighted to make sure that both sides of the drain hole are ground parallel. Mine had a bit of glass cloth/epoxy that had dried over the hole and I had to file it off before the gasket would seal.

On edit: If this is an old gasket that was part of the original tub install I suggest that you replace it.

Forumla, yes, that is the way it is set up. And the instructions are helpful, but that IS the way I've tried installing everything. I also checked the condition of the bottom of the tub, it's perfectly smooth. And I've tried 2 new (different) gaskets to try to stop the leak. Also, how tight should I be tightening the drain? Just snug or should I crank on it? I tried VERY tight, but I'm worried it will damage the tub. What about putting silicone on both sides of the rubber gasket? Or teflon tape on the metal threads? I know I'm just grasping at straws, but I just replaced the metal drain piece and it still ended up leaking.

Well I ended up replacing the PVC pipe with the threads and putting silicone on the washer that goes between that and the tub. Plumbers putty on the drain fitting lip. And it looks like the leak has stopped. I'll cross my fingers it stays that way. Thanks for the help.