Where ever proper planning is done during construction sanitary vertical stakes are fixed on outer faces of walls.
But in the recent years a trend has started to embedd these pipes with in walls in smaller housing. For getting better looks and creating designs inside the toilets and on the outer face from elevation point of view these pipes are hidden by embedding. This causes these pipes to pass through structural members such as beams at times in positions of maximum shear or bending moment. Here even the rings provided for shear in beams are shifted, totally twisted or cut to accomodate these pipes this can be a major point of weakness at times of Earthquakes. Rings / stirrups take the major brunt of the shear forces created by seismic forces and normal loading incase these are only cut or displaced from position then how safe is the building.
Thus care should be taken that vertical sanitory stakes should not pass through beams. Where ever pipes cross beams the structural designer should be informed so that he adjusts the structure accordingly.
In the case of walls chases ar cut indescriminately in all directions ie. horizontally and vertically in both 4.5" and 9" thick walls.This causes weakness in these walls, firstly due to the hammering the mortar joint is weakened, secondly from where ever the chase passes it creates a plane of weakness.These weaknesses can again become fatal at the time of severe earthquakes.
Thus it is very much necessary to take approval of the structural designer w.r.t the postion of vertical stakes and the cutting of chases in load bearing brick walls.If possible provide the G.I pipes on the surface of walls as was the practice in C.P.W.D during the good old days..
It is always advisable to provide the vertical stakes outside the wall since incase of earthquake if these pipes are affected then it would be easy to repair them without breaking the wall and secondly this would not weaken the structural frame.