Gravitas Enterprises is one of the authorised Dealer of Atlas Copco in Prithla, Palwal and Faridabad, India. For screw air compressors, air dryers, filter & compressed air pipe lines. You should be able to hear air very quickly if it has been regularly emptied. Just push the button to bypass the timer or sensing circuit and open the valve manually. As soon as you read this, expect to hear a hiss of air. This further substantiates the drain's efficient operation.