I've done a couple overflow gasket replacements and there is always some flex in the pipe to pull out the old overflow gasket and replace it.
The tub in question is a cast iron niche tub from 1965 with a flat overflow gasket. I removed the cover plate and could not with moderate force get any movement in the pipe by pushing from the tub or gripping and forcing to the side or pulling from the back or applying some leverage off the tub with a screw driver.
How much force is reasonable on the brass pipes to get them to separate from the gasket?
Should I use a hammer and block of wood and tap it sideways from the back or to push it out from the tub side?
Should I try to hammer a scrapper blade under the gasket from the back side?
Is there a way to know if the gasket has the pipe "glued" to the tub or if the pipes are just so inflexible?
LAST THING this repair needs is for the pipes to need replacing.
I have seen many brass tub drain assemblies which were soldered together and there was no movement possible with them. Whether yours will have any movement without breaking anything is something we cannot answer.
Licensed residential and commercial plumber
Is it possible that they silicone the gasket in place? IF so, it's a bear to remove.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014