Toilets feature a large bowl for collecting waste, which can then be flushed or deposited into a sewer or septic tank. Gravity-tank toilets provide a low-pressure flush in homes and other low-use settings (20 to 30 flushes per day). Pressure-assist toilets deliver a strong flush in high-use restrooms (more than 30 flushes per day) where water pressure is too low for tankless toilets. Tankless toilets use a flush valve (flushometer) and a high-pressure water supply for powerful flushing in high-use (more than 30 flushes per day) commercial, public, and institutional restrooms. Prison toilets and ligature-resistant toilets deter vandalism and tampering in special use settings. Portable toilets and commode chairs are used where plumbing is unavailable or people are unable to use a fixed toilet. Macerating toilets (upflush toilets) allow installation in rooms where the main waste line is beyond reach.