Bath not draining thru macerator. Need a fix

[Weegee]

Hi, we have a bath that has been connected through a macerator and won't fully drain. Macerator is a Stuart Turner WC4C. It has been plumbed so that the sink and bath pipes go into a single connector on the macerator. WC on the other side. Bath drains most of the way then we are left with a few inches that can stay for days. We have to flush the loo constantly to trigger the macerator into action to suck out the bath water. When completely gone from the bath the water sits in the trap at a visible level. If we use the sink, the level will come up into the bath again. Need help in finding a fix. Should we plumb the bath directly into the waste water outflow - copper pipe...looks like around 22mm heading out of the macerator? Any suggestions - except remove bath and install shower (bath has to stay) - greatfully recieved. Thanks!

 

[exedon2]

There is a inlet non return valve on that unit probably needs clearing.
Also from memory the instructors tell you only to connect one appliance per connection.

 

[Ben-gee]

Pretty sure they are not designed to take a bath so that’s your main problem.
Most macerators have a minimum of 160/180mm or so for wastes need to be above base of unit, eg need a shower tray to be raised quite high.
Have you enough fall?