It is important to make sure that you drain your air compressor tank as regularly as possibly. In an ideal world you would do this after every use. The reason for this is that water vapour which is in the air builds up each time the air compressor is used. This needs to be removed otherwise the inside of the tank will begin to rust.
The drain valve of the tank can be found on the lowest part of the compressor tank as gravity will mean that any excess water will flow to the bottom of the tank. Drain the tank by turning the knob and opening the valve. To fully drain the air compressor tank, make sure you open the valve as far as it will go.
It is advisable to wear work gloves when undertaking this task as the water will contain traces compressor oil and general dirt, which you don’t want to get covered in. Also, be careful where you drain the compressor tank to avoid staining anything you don’t want to. Once the water has evaporated you will be left with the residue.
If you decide to leave the drain valve on your tank open in order to allow air into it, don’t forget to close it again when you use the air compressor again. If you don’t your air compressor will be unable to build up pressure.