Mark on the waste pipe where you will fit the combination outlet. Allow space for the cut ends of the pipe to fit into the sockets of the outlet (Image 1).
Use a fine-toothed saw to cut out the section of pipe, following the guidelines as accurately as possible (Image 2).
Mark on the wall where you want to route the drainage pipe outside. Do this by temporarily fitting the outlet, or by holding it in the correct position (Image 3).
Drill a hole at the marked position, using a core drill bit. Fit a piece of waste pipe long enough to extend through the wall (Image 4).
Cut back the pipe on the exterior wall to a suitable length for connecting an elbow. Position the elbow on the cut section. Seal with silicone sealant (Image 5).
Fit lengths of waste pipe from the connecting elbow down to a point above, and adjacent to, the water butt. Screw in brackets to fix the pipe.
Assemble the filter unit and place it on the water butt, following guidelines about filter alignment. Fit the hose tail adaptor to the base of the waste pipe.
Use the hose to join the pipe to the filter. For all waste-pipe joints, use solvent cement to secure them in place. Secure the hose with a jubilee clip.