“In the tower blocks, as well as air-tight expansion joints, it would be necessary for the main stacks to change direction at every tenth floor in order to reduce the velocity of flow and to avoid excessive plus and minus pressures in the main stacks.”
Chamberlin, Powell & Bon, Architects “Barbican Redevelopment” April 1959
In other words, the main drainage pipes for the toilets zig-zag down the towers to avoid anything unpleasant picking up sufficient momentum to hit the ground level with explosive force. This is probably not a problem you care to reflect on very often.
The extraction ducts for ventilation and the services ran up the central core of the building.