Question

After construction of watermain, earlier to hydrostatic pressure test, swabbing is approved out. What is main purpose of swabbing?

Answer

Pipelines have to be tested before commissioning to check strength of watermain and absence of leak. Sooner than carrying out hydrostatic pressure test, swabbing is conducted to clear out refuse and dirt left inside pipeline during construction. Swabbing is necessary for pipes less than 600mm diameter since for larger size of pipes; they can be inspected on the inside to ensure cleanliness.

Following carrying out of hydrostatic pressure test, test for water sterilization is next conducted that involves collecting water sample from pipeline. Purpose is to check water quality like colour, turbidity, odor, pH value, conductivity. This is compared with superiority of water drawn from water provide point.