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water quality safeguards. Conversely, the creation of a DMA allows the water
utility to focus more specifically on valves, fire hydrants, pressure levels, and
water quality than in a typical open system. Water utilities are often hard-pressed
to actively manage system valves, and many valves are overlooked for maintenance,
hence, failing to operate in times of emergency such as water main breaks. Good
valve exercising and management practices can be incorporated into DMA efforts
to provide proactive management of these often neglected assets. Water utilities
operating multiple DMAs often have better valve management than those not
employing DMAs. Water quality sampling and assessment should be conducted
during the planning and implementation phases of the DMA, as well as routinely
during the DMA operation. This will give the utility operator the opportunity to
proactively build any needed water quality controls into the design of the DMA.
Good water quality can be maintained by properly configuring the boundary or
4
performing periodic flushing.
Minimum flow and pressure requirements for fire flow and insurance: During the design
phase of a DMA it is important to properly assess the impact the creation of a
DMA has on the ability to provide sufficient flow and pressure in case of an
emergency.

There are several design options to meet fire flow and insurance requirements. Mul-
tiple or redundant feeds have proven to be a successful method of designing DMAs,
where only the primary feed (or feeds) is equipped with a DMA meter and the stand-by
feed (or feeds) is equipped with a PRV that only opens up in case of an emergency (see
Fig. 16.17). The lead and stand-by feed can be located in the same chamber or at differ-
ent feed points on the DMA boundaries. Another method of meeting the fire flow
requirements while accurately measuring the DMA inflow is to use check valves or
pilot-controlled hydraulic valves in place of closed-gate boundary valves. When fire
flows are required, the system pressure will drop within the DMA causing the check
valve or hydraulic valve to open thereby introducing additional flow as required.

16.6.3 Initial DMA Installation and Testing
Following the initial design phase the DMA needs to be set temporarily and field mea-
surements gathered in order to verify the integrity of the DMA and to gain the data
necessary for the DMA chamber design. The DMA needs to be set up by closing all
identified boundary valves and verifying the status of already closed valves. The sup-
ply into the DMA through the selected feeder main/s needs to be monitored by using
temporary flowmeters (e.g., electromagnetic insertion flowmeters, or clamp on ultra-
sonic flowmeters).
Next the integrity of the DMA boundaries should be assessed by conducting a
“pressure drop test.” During this test the pressure is dropped within the DMA in vari-
ous steps by operating the valve or PRV controlling the inflow to the future DMA. Such
tests should be conducted during the minimum nighttime flow period (between 1 and
4 a.m.) in order to avoid customer consumption disruption that would generate com-
plaints. This period needs to be adjusted to any local differences in demand patterns.
The steps in pressure reduction should be in the range of 10 psi (7 mH) to 15 psi (11 mH)
down to the pressure level where the minimum required pressure at the critical zone
pressure point is set. In order to monitor if the DMA is hydraulically discrete or not,
several pressure loggers need to be installed outside the DMA boundaries prior to