Contamination of pipeline by rodent carcass in Porvorim, Goa : Need remedies

We live in an independent house in Porvorim, Goa. A rat that consumed poison, got into the vent for the overhead tank and into our pipe line. We have opened the taps, pipes in the whole house. In some pipes the dis-integrated body parts came out. The overhead tank has a capacity of 1000 litres. We drained all the water and kept the tank and pipes dry for about 12 hours.

 We have used some bleaching powder this morning, by first mixing it in a bucket of water and then adding the solution to around half tank( about 500 lt. )of freshly pumped water. Tomorrow we intend to drain the water from the overhead tank . Then we wish to use a solution of Potassium Permanganate to half tank of fresh water, keep it in the tank and pipeline for about 20/24 hrs  and then drain it before we re-fill with fresh water.

What is the % / ratio of Pot. Permanganate to be used ? Will this process render the water safe for consumption? Any other procedure that can be undertaken to ensure the safety of the water supply / sanitize the pipelines? Please advise.