muffler needs fixing very often

I have been using santro gs 2001 model .the vehicle has been giving me very good service except for the muffler which developed holes requiring garage repair from the third year.since then this had to be repeated at least twice in a year.the service people attributed the problem to catalytic converter.last year a new muffler had to be fitted.

Where (location) were the holes? A catalytic converter is before the actual muffler - so a jam in the convertor should generally have pressure build up earlier and not later in the pipe.

Is the whole exhaust assembly properly assembled? Missing "ties" can cause the exhaust pipes etc to shake more and cause pipes to develop holes. Also rust/potholes/lower ground clearance are other things that COULD play a factor here.

The 'rusting silencer' problem is a known issue with the santro. Had changed the same on my car once and then did local repair on the same twice later on.