Since 2011 the main sewers are the responsibility of Thames Water and if you discover a blockage in the shared or public drains then your first call should be to Thames Water blockages on 0800 316 9800.
You should then alert Alison Mitchell who runs the Froghall Help scheme so she can warn the other affected residents to reduce water use until the problem has been fixed.
The section of the sewer from your house to the shared drain is considered to be your property and if you call Thames Water they may charge you to clear a blockage in that section. If you fancy clearing the blockage yourself then you can borrow the FDRA drain rods. Call the Chairman or the Secretary of the FDRA to find out where the rods are kept. There is a loan book - please sign the rods out and sign them in when returned.
Above is an overview of the system showing both foul and surface water drains. This map is incomplete and may not be completely accurate but should help you understand on which section of the network your house is located. Here is a more detailed version of the same map.
If you know of any inaccuracies in the map please let us know.