Dead end distribution system

The dead end (tree) system is a layout in which one main runs from the reservoir through the town and sub-mains branch from it like a tree; each branch ends at a dead end and has no connection with other branches.

         Sub-mains / branches
              |   |   |
  Reservoir ==============+=== Main
              |   |   |   |
           branches end (dead end)

Merits

1. Simple to design: the discharge in each pipe is known, so sizes are fixed without trial and error.
2. Fewer valves and less pipe length are needed, so the cost is low.
3. Easy to lay and maintain; the discharge and head loss are easily found.
4. Suited to towns that have grown without a planned pattern and to hilly or linear settlements, where it follows the roads.
5. Individual pipe diameters are economical, as the pipe size decreases away from the main.

Demerits

1. Water in the dead ends is stagnant, which gives bad taste, bacterial growth and sediment deposits. Scour/blow-off valves are needed at the ends and must be flushed regularly.
2. If a pipe breaks or is shut for repair, all consumers beyond that point lose supply.
3. Pressure at the far ends is low, and it varies with the demand on other branches.
4. Discharge for fire fighting is available from one direction only, so it is limited.
5. Extension of the system reduces the pressure in existing branches.