When an old drain need to be replaced then a retrofit drain is the answer. The issue is it does make the drainpipe slightly smaller but it is a good alternative.
There are times when an old drain starts causing problems and need to be replaced. Instead of cutting out the old drain, you can install a retrofit drain by inserting it into the old one. Al you have to do then is tie the roofing membrane to the new drain flange.
Waterproofing and Leak Specialists