Drainiac (2000)

If you expect to see anything like the monster on the cover, you'll be sorely disappointed as the only thing you'll see is some slime and some things that look like meat tentacles.

Julie's abusive dad leaves her to clean up an isolated old house he just bought.  When her friends decide to bring her lunch, they are followed by a creepy bully who tries to assault one of the girls.

There is green slimey goo in the basement. It eats a hobo.  Yet when the kids are there, it does not appear.  The meat tentacles appear in Julie's dream and also erupt from the toilet to devour the unsuspecting bully.

A stranger shows up at the door, claims the house is haunted by a ghost in the pipes and asks for help doing an exocism.

There is not much monster in the film.  Just some green goo, a few meat tentacles and some cgi stuff during the exorcism.