There are many opinions on what the idle vacuum should be for a vacuum cleaner. Some people believe that it should be as high as possible to ensure that the machine can pick up as much dirt as possible. Others believe that a lower vacuum is better, as it will save wear and tear on the motor. In general, a vacuum cleaner should have an idle vacuum of at least 16 inches of water column. However, you may need to adjust this number depending on your specific machine and needs. Always consult your user manual to get the most accurate information.