The SoClean 3 no longer has a visible check valve that needs to be changed with the filter. The check valve has moved within the unit, and additionally there is a back up PTFE membrane filter in the unit to preventing the water from entering the SoClean 3. In addition, no side slot plug is required with the SoClean 3. There is only one hose slot, where your hose must rest and lid closed in order to run a Maintenace Cycle.