Drainage Pipeline Connection

Since our existing drainage pipeline connection is blocked (passes through the backside common way of our ancestral property) and which cannot be cleared because our neighboring landowner (my uncle) extended his kitchen room by occupying the backside common way which has now blocked the waste water, we have been advised to take a new drainage pipeline connection through the frontside common way without affecting his house. Our neighboring land owners are now not allowing us to take a new drainage pipeline connection through the frontside common way. As per the "Will" it is clearly mentioned that the front and back ways are common to all the landowners and can be used equally without creating problems. Our house is at one end of the land and our existing water connection, drainage connection & electricity connection are passing through the backside common way crossing 6 houses (south side) & connecting the main Municipal Authority Connections for more than 17 years. We don't have an option to take the connection on the north side of our house because it belongs to another landlord who is not connected with our ancestral property. Kindly advise me on what should be my next step to find a solution for the drainage pipeline connection which is blocked for more than a week now.