Having an issue with tub drain plumbing. Previous homeowner was an idiot and didn't disclose much about house. Now I'm left to fix it the right way. They remodeled a bathroom and took out a portion of cast iron pipe used for the tub. Not sure if he broke it, it was corroded, or he was told to do this... He necked in a PVC pipe which reduced the diameter of the pipe by a quarter inch. This left a gap of about 3/8" between the lower shoe and tub. The only gasket I can then get in there without flexing the pipe is what I thought was the thicker (3/8") upper shoe gasket. Since the durometer of the rubber isn't very high. Tightening the drain pushes the gasket out, causing a leak. Leaving it so it isn't pushed out also has it leaking as there's not enough pressure to maintain a seal. What's the best way to go about fixing this? It would be nice if they made a taller or adjustable shoe so I could put in a smaller gasket and seal it down tight. Are there any other necks I could put in place to bridge that gap and seal it up?

He necked in a PVC What's :necked"?If this were my call I'd tear everything out. Convert to PVC at the cast iron and do the job correct, Let ne know what you decide, Tom

He shoved in a pvc pipe OD that fit the ID of the cast iron. So instead of having a 4.5" ID cast iron, there's a 4" ID pvc pipe pushed into it and sealed up. This reduction in the diameter of the pipe left the 3/8" gap between the shoe and tub. Can't recall from memory but not sure if the disconnected the cast iron at a junction or cut it. If he cut it, I'm going to have a harder time tearing it all out to put back together as I'm left with nothing to connect to. It's why I was wondering if there's any drain shoe taller, low angled pipe, or flexible lines that can be set in there to fix.

I don't know if you have access beneath your tub, but you have many options to replace your tub drain or even extend the existing one.

Tub Drain Product - Bing Images (http://www.bing.com/images/search?q=Tub+Drain+Product&Form=R5FD19)

If in the USA, a Loews, Ace Hardware, or Home Depot can guide you to fairly easy solutions to your tub drain gap, and the leaks they have caused.

I would remove the drain and take it with me along with the old drain measurements for correct sizing.

Start with removing his shoe, and fitting to the original configuration.