Page 133 - Trenchless Technology Piping Installation and Inspection

Coatings and Linings for Potable W ater Pipe Distributions 99

3.6.1 Objectives of Prelining Inspections
The purpose of a prelining inspection is to ensure a successful liner
installation. This inspection provides a good idea of the degree of
cleaning required to prepare the existing pipe before the start of a lin-
ing operation. A prelining inspection may also reveal the need for
other forms of preparations required before lining, such as removal
of protruding lateral service connections. The state or presence of the
following issues may be revealed during the prelining inspections:

• Leaking valves and ferrules
• Leaking stop taps
• Dropped joints
• Protruding ferrules
• Structural problems (cracks, holes, and so on)
• Cleaning and possibilities for re-cleaning requirements
• Pipe bends that can affect cleaning and lining processes

3.7 Pipe Cleaning Methods
Cleaning of existing water pipes is prioritized based on the age of the
pipeline and the frequency of the problems it encounters. In most of
the water pipes, sediments accumulate and biofilms develop, increas-
ing the risk of color, taste, and odor problems, along with the chance
of coliform regrowth.
Cleaning must be performed on the section of the existing pipe to
be lined. Before isolating and cleaning the section, water flow must
be stopped or bypassed. The section of pipe will then be emptied and
cleaned. The cleaning technique chosen depends on the pipe mate-
rial, previous lining, and entry point locations. It must be noted that,
if the structural condition of the existing pipe is poor and the pipe
wall is thin, then some cleaning methods may result in damage to the
pipe section being cleaned. Figure 3.4 illustrates a conventional clean-
ing method using a steel rod. Table 3.2 presents a summary of water
pipe cleaning methods.

Steel rods
Machine
Cleaning head Water supply
Water/debris

FIGURE 3.4 Rack-feed boring machine using steel rods. (Source: Water UK.)