Distribution System Operation for Class S
The distribution system is where treated water either keeps its quality or loses it, and it is
where the operator's work is most directly a public health barrier.
Pressure and hydraulics
The purpose of the distribution system is to deliver an adequate quantity of safe water at an
adequate pressure, at all points, at all times.
- Positive pressure everywhere is a contamination barrier. When pressure is lost, the gradient
that keeps contamination out of the main is lost with it, and water can be drawn in through
cross-connections, leaking joints and submerged appurtenances. Systems are generally operated to
maintain a minimum positive pressure at all points under normal conditions, with regulatory
minimums commonly cited in the region of 20 psi; the applicable requirement comes from the
regulation and should be confirmed with