Problems with Ext hard drive

I have had problems with my external hard drive when i go to delete some of the content i have on it it will delete it but it doesn't free up any space that that content took up. i use ntfs mounter to i can write would that have anything to do with it. if someone can help thanks.

The external hard drive must remain attached (mounted) to your Mac when you empty the trash.

Thank you very much that was really helpful. Why do you have to do that?

Have you ever tried to throw the trash away at home when you can't find the garbage pail? Same reason the drive must be attached and mounted before you can empty its trash.