Water is the only way to get rid of popcorn ceilings. Careful not too much. I recommend removing the carpet or protect it with plastic taped to the baseboards. Lightly spray the ceiling and let the water soak in but only do small areas and careful not to get the paper on the drywall too wet...then you will be redrywalling. Then with a wide drywall scraper scrape the popcorn onto the floor. Be prepaired to texture the ceiling with knock down or have it finished further because popcorning is a time saver to drywall finishers. They don't have to finish the ceiling as well as the walls because of the cover up characteristics of the medium.