Over the recent years, the emphasis on sewerage has increasingly
switched from provision of new services to maintenance of existing service at
acceptable levels. As a consequence the need is now to rehabilitate existing
systems rather than construct new ones.
The common methods of rehabilitation consist lining of the sewer pipes
and that was out of the question since it decreases the diameters of the already
under size sewer lines.
So that, hence, it was concluded that the best method for rehabilitating the
existing system was by total replacement of the undersize sewer lines. This should
be done using sewer pipes with better quality material, such as PVC, GRP or first
class concrete pipes.
Modern water and wastewater pipe is either organic or inorganic in
composition. Today's organic pipe is made of petroleum-derived plastic, which
contains preservatives, antioxidants, and stabilizers to slow down the gradual loss
in strength that occurs with organic materials[1].
So that redesigned the existing sewer system in AL-Karadda district
within the city of Baghdad by computer with the use of QBasic language. The
design consist concrete pipes in once and plastic pipes in other to find the best.
Based on the results, it was concluded that the plastic pipes needed
gradient (Smin) less than concrete pipes (0.004 m/m for plastic, 0.005m/m for
concrete), the max. soil cover for plastic pipes was equal to (3.59 m) while for
concrete pipes it was equal to (4.25m).In addition the network redesigned on the
min. commercial concrete pipe diameter equal to (200mm) while for plastic pipes
equal to (250mm) and that will increasing the capacity of the network.