You might ask why swabbing a new main prior to chlorination is important?
Well for many reasons.
- To remove air. Trapped air will cause issues with any pressure test and will prevent chlorine from correctly contacting parts of the pipe, leaving potential bacterial contamination prevent post disinfection.
- To remove debris. The swab effectively scrubs the pipe clean and pushes out any contaminants. This means no dirt is left, resulting in a cleaner pipe an therefore less chance of failure. It also prevents issues later such as stones from moving and blocking valves etc.
- Proving the pipe run. Is there something in the pipe work that may cause a blockage? By running a swab it is clear that the pipe work is clear and there is nothing present that may cause a blockage later.
Swabbing should be performed on all new mains pipes and should be done prior to any chlorination or testing. Swabs placed into the pipe should be clean and free from contamination and ideally numbered and identified to ensure retrieval.
Once swabbing is complete the swab should be examined and photographed and if contamination is present another swab should then be run.
Once swabs leaving the pipe work are clean then the process of pressure testing and chlorinating the new main can begin.
You can see below the amount of debris that can be left in a main if swabbing is not correctly performed. Would you want to drink that?
