Bangalore Water Supply & Sewerage Board [Bwssb] — Main sewerage line blocked in the road

Address: 626, 1st A main road, opp. Pavani Sankaramangalam Apts, Byrappa Layout, Whitefield, Bangalore-560066

Sewerage line is blocked and the drainage water is logged in the first chamber near the house compound.
We tried fixing it by the local available persons but they could not fix it.
They are telling that the water is reversing from the main line...