Hi there and thank you for your question,
I will try to assist you with your legal question but please feel free to ask as many follow up questions as you like until you are 100% satisfied.
If the owner of the apartment did this installation without the permission of the Body Corporate (I'm assuming that there is a Body Corporate involved in this building) then your solution is quite simple:- Complain to the Body Corporate and make them to something about it.
The owner MUST have obtained permission from the Body Corporate before he could build the further toilet, and he MUST have obtained your personal permission before he could install pipes on your balcony.
The owner CAN'T simply do this without permission of the Body Corporate, or without your permission.
He just can't.
Your only course of action is to make the Body Corporate get the owner to comply!
You should do this in writing, addressed to the Chairperson of the Body Corporate.
If my answer hasn't answered all of your questions, please send me a REPLY with follow up questions so that I can continue to assist you in this same thread for as long as you need. Let me know if you need more advice - dont just rate my answer as "bad".
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Good luck and best regards,