If you are using the Shower Base, the filter will only filter out debris, it won't filter out soap water.

Install a filter inside the ENSUITE Shower Base

To avoid any debris entering your pump or HOTTAP, you can install a filter inside the ENSUITE Shower Base. 

To do so, simply install (via quick-connect) a suitable filter. If you have the HOTTAP Outing or HOTTAP Nomad, the included Joolca filter is perfect.