Rehabilitating small-scale piped water distribution systems
Technical note 4 on drinking-water, sanitation and hygiene in emergencies
Step 5: Repair breakages
Repair the pipeline
Start at, or near, a source of supply and work outwards into the distribution system. Repair the pipeline in a stepped manner. For example, referring to Figure 4.4, start with the section between the source and the service reservoir.
Follow this repair by rehabilitating the main pipeline from SV1 to SV5, making sure to close valves SV2, 3 and 4 and any service connections first. Select a pipeline section that can be easily isolated by existing stop valves, of say 500 to 1000m apart.
Arrange to install washout valves (such as WO1), and fire hydrants (such as FH1) if none can be traced in the selected section. Before starting any repair work:
- Locate other underground utilities at work in the area, and liaise with their maintenance departments, if necessary.
- Route traffic away from the work area.
Excavate and expose the broken sections of the pipelines. Protect the repair crew from trench collapse. This is normally not a problem with small diameter pipes but if the ground is very loose protect them by shoring the work area as illustrated in Figure 4.6.
Methods of repair
Use simple methods of repair that will take the shortest time to restore services. Examples of simple methods:
- The damaged section may be replaced by use of repair pipe clamps, as shown in Figure 4.7.
- Repair of cracks and breaks in steel pipes by welding.
- If there are multiple breaks, it may be quicker and easier to replace the whole section with a new pipe. A temporary pipe run above ground is satisfactory for an emergency supply.
Replace pipe support structures such as concrete anchorage and thrust blocks, if necessary. Backfill around the pipe with selected material such as dry sand or washed stone. The remainder of the excavation can be filled with the excavated soil. Leave the pipe joints exposed so that they can be observed during water pressure testing.