Read the instruction carefully. Practice on a clean toilet prior to needing it for an actual clog situation. The silicon adapter (boot) – with its extended flaps – will ensure an airtight seal when the unit is inserted, and then held at about a 45º angle downwards… prior to pressing the button (trigger). Make sure you push the silicone adapter (boot) fully into the toilet – until you can push no more – then slightly lean the WAND downwards at about a 45º angle.  You will then have an airtight seal.  Hold firmly with BOTH hands to avoid any “kick back”.  Failure to do this could result in unpleasant splash-back! You don’t need to try and siphon any of the existing water out.  A water filled environment helps the unblocking process significantly … SurePlunge uses the water in the bowl to forcefully push the blockage out of the way with its compressed CO2. Each time you use SurePlunge you will need to insert a single-use CO2 cartridge.  Simply open the top of the unit, place the cartridge and screw the inlet cap back on.  This action punctures the cylinder and the SurePlunge is then ready for use. Easy as 1-2-3: Using both hands, insert the SurePlunge fully into the toilet. Angle it downwards at about a 45º angle.  This makes the air-tight seal. ** The silicone head’s upper flange will also help prevent splash-back. Press button (trigger) to release CO2 gas.  **Expect a slight “kick-back”.