flange inside waste pipe but net secured to waste pipe
Hello. I just installed a new flange into a 3" waste pipe. I removed the old cast iron flange and therefore cannot place new flange over waste pipe due to pieces of old flange still present. I used a "twist and set" replacement flange, however, it did not secure to the waste pipe. The flange is inside the pipe though. My question is, how would i go about securing the flange to the waste pipe. Also, what is the reason for securing it to the waste pipe. It this due to possible leaks? Thanks.