Page 346 - Water Loss Control

Contr olling Real Losses—Pr essur e Management 315

often cost-effective. We will be discussing how the hydraulic solutions work later in this
chapter.
Most tanks and reservoirs have an overflow pipe. If a utility wishes to discover if
overflow is occurring, it is a simple task to inspect the point where the overflow pipe
dumps water. If there is recent evidence of water being discharged, then either level
should be data-logged and compared with the overflow level, or if data-logging tech-
nology is not available a simple solution is to locate a ball in the overflow pipe and
inspect the position of the ball each day. If the ball has come out of the pipe then there
has been an overflow situation.
Pressures and levels should be monitored and the level of loss analyzed. A simple
cost to benefit exercise will identify if a new system of control is warranted.

18.6 Fundamental Monitoring Points
For any pressure management project, it is first necessary to monitor as a minimum the
following points:

• Supply nodes
• Storage nodes
• Critical nodes
• Average zone point (AZP) nodes

Supply nodes could be considered as any point, which supplies a system or subsec-
tor of a system. A supply node could also be an outlet point from one zone to another.
In some cases it may be necessary to monitor bidirectional flows.
Storage nodes would be any reservoir, tank, standpipe, or location where water is
stored.
A critical node is a location point where supply may be at its weakest, for example,
a high level within the system or a point where there is high head loss in the supply
pipe. Alternatively it could be a point where a user cannot be left without water, for
example, a production plant or hospital.
An AZP node is a location, which is chosen to be representative of the average con-
dition, (ground level, pressure, head loss, and the like.) within the system or zone.
Methods for properly identifying AZP points are discussed in Chap. 10.

18.7 Flow Measurements
In general flow measurements should be taken at any supply or exit point as discussed
above. A supply point may be a pumping station, treatment plant, storage facility, well
or bulk transfer point to the system or zone. It may
be deemed necessary during a demand analysis, to
measure demands from large consumers, if they are The longer the measure-
considered to be large nighttime water users.
ment period the better, howev-
Measurements should be taken for a minimum er measurement periods are
of 24 hours, but preferably for 7 days or more, the
decision on how long to measure for usually comes usually limited by the cost.
down to cost.