Page 356 - Water Loss Control

Contr olling Real Losses—Pr essur e Management 325

demand periods. In some cases it may be advantageous for both the utility and the
customer to install an on-site storage facility, if one is not already installed. Once the
large consumer has some storage, either flow or pressure-sustaining valves can be used
to control the demand of the large consumer and minimize the peak impact caused
through high-localized head losses.
Site visits for all large consumers are a must to ensure that their demand needs and
emergency needs are taken care of properly. The cost of these surveys and in some cases
retrofitting fire sprinkler systems or providing storage may sometimes be included in
the project cost. This would be so in the case of a customer who didn’t want to change
their system and was holding up the whole project. Obviously this would only be done
at the utilities expense in favorable payback situations.

18.17.5 Sectors with large seasonal variations
In sectors with large seasonal variations it may be necessary to install multiple feeds, or
valve installations in parallel. The parallel installation would consist of a large valve,
which will provide high flows during peak conditions, usually at weekends or holiday
periods in the case of tourist areas. The smaller valve would then function most of the
time. In many cases where a controller is installed, the controller need only be installed
on the valve, which is most active. In certain cases the larger valve will function most of
the time with the small valve operating just at night during periods of minimum night
flow. See Fig. 18.21 for an example setup.

18.17.6 Sectors with Weak Hydraulic Capacity
In sectors with weak hydraulic capacity it may not
be uncommon to find potential for pressure reduc-
tion at night, whereas during the day there is not Pressure management can
sufficient pressure. Pressure reduction at night how- be undertaken at off peak
ever can often still be justified and would depend hours only, if systems are
on the cost to benefit analysis for final decision. As
weak during peak demands.
mentioned earlier, often pressure-sustaining valves

FIGURE 18.21 Parallel installation can be used to extend fl ow range.