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284 Cha pte r S i x tee n

clearly suggest that DMAs are applicable to North American networks when certain
design criteria are properly addressed. Two DMA design elements of note in the North
American water industry are fire flow capabilities and water quality. However, exten-
sive field testing in North American water utilities revealed that, by following some
simple design rules, it is possible to create and operate a DMA and still provide the
necessary fire flows while maintaining adequate water quality. The design rules dis-
1
cussed in this chapter draw from the research findings of the above project and can be
applied to the use of the DMA technique in any setting, and not just the North Ameri-
can water industry.
The most important factors that need to be taken into consideration when designing
a DMA are
• The economic level of leakage or the economic intervention frequency needs to
be considered since it will impact the optimum size of the future DMA.
• The types of consumers (industrial, multifamily, single family, commercial, and
critical customers such as hospitals, and the like.) need to be assessed and
considered during the design phase.
• Existing pressure control zones should be assessed and if possible converted
into DMA. This is the easiest and most economic way of creating a new DMA.
• Variations in ground elevation need to be assessed thoroughly.
• DMAs should be designed in a way so that new boundary valves are located on
smaller mains.
• Existing check valves and closed PRVs should be used as DMA boundary valves
providing additional back up in case of fire flow emergencies.
• A boundary should be designed not only to fit the broad design criteria for the
DMA, but also to cross as few mains as possible. The boundary should follow
the “line of least resistance” by using natural geographic and hydraulic
boundaries. The aim is clearly to minimize the cost of installation, operation,
and maintenance. A hydraulic model is particularly useful to identify existing
hydraulic balance points where a DMA boundary valve can be closed without
modifying the existing operation of the network, thus limiting potential pressure
or water quality problems.
• Transmission mains, service reservoirs, or tanks should not be included in a
DMA.
• Water quality considerations have to be addressed and water quality should be
monitored prior to and after the installation of the DMA.
• The targeted final leakage level should be defined to make sure the DMA meter
and PRV are not oversized once the backlog of leaks was removed.
• Minimum flow and pressure requirements for fire flow and insurance purposes
need to be assessed.
• Minimum and maximum pressure at the critical zone point should be assessed.
• Looping and redundancy requirements need to be assessed.
• System changes required for DMA installation, like the number of new valves
required, installation of meter point(s) and chamber(s), and and so on. should
be considered.