Atmospheric pressure is limited to 14.7 psi (at sea level), This being said the limitation on vacuuming liquid vertically is approximately 28 feet. However, we have equipment outfitted with our vacuum trucks that allow us to vacuum to deeper depths. Recently we vacuumed to vertical depths of 130'. This has enabled us to complete the job, where others could not perform the task even after bringing in additional hydrovac vacuum trucks to provide additional vacuum support. Our customer was very pleased with the cost saving, not to mention lost time and expense associated with 4 previous contractors who could not complete the job.