I dunno how your piping work, but usually the pipe will not go so near with the drainage pipe...

Old condo pipe some are pipe go from ground and go up.. some are from up to down..

But for ur case, maybe u ask for drawing from management..
And usually condo unit pipe rarely burst one la... usually la
If there is a burst, the leak will be very powerful and spread round round area watermark one.. i dunno for ur case la.

Best option now is do PU injection and hope it works..
If dun works, then only do hacking..