Your problem is quite common and not nearly as difficult to fix as you might imagine.

The flange and cup shaped metal part with the cross at the bottom that you are looking at is properly called the "Tub Basket". On the end of the drain line immediately under the tub hole there is a casting called the "Tub Shoe" that has female threads. Once the Tub shoe is properly aligned with the tub hole from the bottom we apply plumbers putty to the underside of the flange on the tub basket and insert the basket through the tub hole from the top and screw it into the tub shoe. As the basket is tightened down from the top it in turn pulls the tub shoe upwards to insure a tight seal. (There is also a rubber gasket between the top of the tub shoe and the underside of the tub).

Such is common to all things, in time the plumbers putty will dry out and crack resulting in a leak. To repair the leak you will need a "Tub Basket Wrench" to unscrew the tub basket. Once you have the basket out you can clean the underside and apply new plumbers putty, which is the industry norm, or you may elect to apply a generous layer of cf clear silicone sealer (Plumbers Goop) then insert the tub basket back into the hole and use your basket wrench to tighten it in place. As you tighten the basket in place the excess plumbers putty or silicone will squeeze out around the flange. That is to be expected and it is a simple matter of wiping the excess away when the basket is tightly in place.

A word of caution here. If you use plumbers putty the drain can be used immediately but if you elect to use silicone you must allow 24 hours for the silicone to completely set.(personally I prefer the plumbers putty because once a basket is set in with silicone it is nearly impossible to ever remove again, and contrary to public opinion, silicone will leak in time due to the minor flexing of the tub in normal use.)

Some handymen will tell you that you can remove the basket by inserting the points of needle nose pliers through the cross and turning the cross that way. Don't you believe it. When trying to remove a basket in that manner there is an extremely high risk that you will break the cross out then you will have a real chore trying to remove the basket.

There are dozens of varieties of tub basket wrenches ranging in price from about $7 for the simple cast iron type to well over $60 for the professional grade type. Fortunately even the el cheapo cast iron type will do fine for the limited use that a homeowner might need.

You can find a basket wrench in any local hardware or home supply store.

(If you would like an illustration send me an email requesting it, and i will be glad to return it to you)

to add to what LP said, if you do break out the cross, it is a simple fix. get a Dremel tool with a cutting wheel, actually a couple wheels cause i guarantee you will break them. cut the basket vertically into 2-3 pieces and pop them out. then install a new basket as laid out above.

you just want to cut the basket. you will score the female threads some, but just don't let it cut all teh way thru the shoe or you will be replacing it as well.

if you do this, WEAR SAFETY GLASSES!!

If you don't have a dremel tool you can do the same thing with a Stanley "mini hacksaw".

I'm having a similar problem. I did get the special tub basket wrench (a cheap Danco version) and the wrench still pops out of the basket rather than turning. Seems that it's just really stuck.. am I going to have to hacksaw it out, or is there anything else I can try? Kinda annoying to have bought the special tool for something and have it still not work..

pad the top of the basket wrench with a rag and press down hard while turning the basket wrench with an adjustable wrench.

Thanks. I tried that.. even with a cheater bar on the handle, it still won't budge.

I bought a nice bulky wrench to use. Fat sucker. I could remove the basket with one hand using the wrench. The gasket between the tub and the drain seemed to be in great shape, despite not being 100% centered.

I cleaned everything really well and put plumber's putty around the opening. I tightened it down pretty well, just being careful not to overdo it.

I guess it could have been the fact that the basket wasn't tight enough, evidenced by how easy it was to remove. The bottom two threads of the basket were the only ones with the black residue from pipe. When sticking my finger in the drain, it still feels like it might have half a centimeter of thread distance left, but it's really tight, now.

I'm more confident now that the gasket under the tub has sealed better. That may have been the culprit. (I so hope!)

Great info ... thanks for the posts. I believe the gasket under the tub is leaking.

How do I replace the tube gasket between the Tub Shoe and the bottom of the bathtub?

Remove the old drain flange using the tub drain removal tool. The drain removal tool resembles the shape of a dumbbell. The ends of the tool are sized differently to accommodate the two most common types of drain flanges.