I don't understand what kind of fitting you are describing. The only fittings I have ever seen on the bottom of a water heater is a hose bib. These are usually a piece of crap and a person is well advised to replace it with a ball valve. That said, it does not sound like the tank itself is leaking, so if you can figure out how to replace that "thing" with a ball valve, you should be OK at least for awhile. 10 years is well into middle age for a water heater, but I'd stay with it until it really leaks. As far as tankless is concerned, the are wonderful if you have deep enough pockets to buy one, enlarge your gas or electrical supply service to handle the added power requirements, pay for the installation, pay for the high operating costs, and the frequent and high cost to maintain them. Also, you should not be too concerned about having truly hot water in the winter if you live where it gets cold. Seriously, I would suggest you search the archives of this forum and see what others have experienced with these things. For the most part, they are very negative. They seem to be a wonder concept that just hasn't been developed to make the a good choice.