If you have a tank, mount the regulator to it and turn on the air to pressurize. While hosing or soaking the regulator, press the purge button to wash inside the second stage.

If you don't have a tank, be sure the regulator's dust cap is firmly in place so water doesn't get into the first stage. While hosing or soaking, do not press the purge button. Without air pressure in the hoses, water will enter them.

Learn what you should do at the end of each day's diving in "How To Wash Your Regulator".