Yes for alteration and modification the permission need to be obtained through the ward officer.

1) obtain prior permission of muncipal corporation for construction of private toilet inside house 

1. YES, It is absolutely necessary to take BMC permission to build WC or any other drainage outlets in a residential house. No permission would mean prosecution and penalty.

2. BMC does provide permission, on medical grounds, subject to following due procedure of law and documentations.

Keep Smiling .... Hemant Agarwal

This is an internal modification without altering the structure, hence in my opinion, if landlord has no objection, you may not have to strain to obtain permission from the local civic body for this minor alteration which do not need structural changes.

Yes bmc permission needed

Do you have a valid and subsisting tenancy agreement with the land lord? If so, does the agreement state seeking permission to make alterations and putting up additional construction with the permission of the land lord? If so the same must be obtained in writing before doing so, then give a notice of your desire to put up a toilet at your own cost within the demised premises. If the landlord refuses, as he has done in your case, then proceed to file a civil case before the competent authority or civil court and seek permission from it based on your tenancy agreement.

Hello,

Yes in order to take new WC permission from BMC has to be taken.

If you are making internal arrangement from the one main WC, then no connection is required. 

Regards  

Actually for internal alterations permission of bmc is necessary. People do it without permission also. Legally it is needed.