Unlike oil sealed ones, water - ring vacuum pumps are capable of creating vacuum up to 710mm Hg only which is far less than what can be achieved by the former . But still are preferred in chemical and pharmaceutical industries. These prove economical and require less maintenance. Water is used in place of costly oil and no hassle of frequent oil changing. Requires less energy to run and enjoys longer life. Even noise otherwise create no pollution , no fumes and produce every little nosie. Higher vacuum through them can also be achieved when made to work as backing pumps in systems. Suit all applications covered by oil sealed pumps.