I have a large cast iron tub sunk into about 3 inches of concrete in an old building that I am working on. It's not going to be taken out or moved. The previous overflow valve has been epoxied over and the previous drain pipe is rotted through. The wet wall is open and I need to drill a hole through the tube to put in another overflow valve. I know this is not recommended by the manufacturer, but given I'm not taking out the tub, and that the tub is close to 90 years old I doubt I the manufacturer is still around. I really don't have a choice but to drill hole for the overflow valve in a 90 year old cast iron porcelain tub, does anyone out there have any suggestions?
Appreciate it in advance.
PS. The guy actually doing the work is a real tradesman but has not had to ever drill through a porcelain cast iron tub before. He's too busy actually working rehabbing the bathroom right now to post, so I'm the guy putting it out there.