Are there different barrel sizes of trip lever plungers for a tub drain? My plumber said that he length is fine but he said that he thought the barrel diameter was too small to hold water.

Yes, barrel sizes can be different. If there is a manufacturers name on the existing tub waste assembly you can order the correct replacement part from them. Otherwise, purchase a TOE TOUCH POP UP replacement drain kit... lets you swap out the face plate and strainer ONLY and then there is no need for the barrel at all!

Mark

Attachment 47894

Yep, easiest way to go and a lot easier to fix.