Hot Start Files are used to define the initial heads and flows in SWMM5

Subject:  Hot Start Files are used to define the initial  heads and flows in the nodes and links of the model.

The creation of the Hot Start File for your sanitary, combined or stormwater network is a three step process:

1.   Save the 1^st Hot Start file using an empty system as the initial conditions,
2.   Use the 1^st Hot Start file as the initial condition in the second run and Save the 2^nd Hot Start File
3.   In the 3^rd Run Use the 2^nd Hot Start file as the initial conditions of your network.
4.   It is not necessary that the Hot Start Files be exact in the initial depths or flows but only approximate so that the network in not empty.