3 August 1998
Effective Population =
+ Resident Population
(10) Capacity factor. The multiplier which is applied to the effective population figure
to provide an allowance for reasonable population increase, variations in water demand,
uncertainties as to actual water requirements, and for unusual peak demands whose
magnitude cannot be accurately estimated in advance. The Capacity Factor varies inversely
with the magnitude of the population in the water service area.
(11) Design population. The population figure obtained by multiplying the
effective-population figure by the appropriate capacity factor.
(12) Required daily demand. The total daily water requirement. Its value is obtained
by multiplying the design population by the appropriate per capita domestic water allowance
and adding to this quantity any special industrial, aircraft-wash, irrigation, air-conditioning, or
other demands. Other demands include the amount necessary to replenish in 48 hours the
storage required for fire protection and normal operation. Where the supply is from wells, the
quantity available in 48 hours of ,continuous operation of the wells will be used in calculating
the total supply available for replenishing storage and maintaining fire and domestic demands
and industrial requirements that cannot be curtailed.
(13) Peak domestic demand. For system design purposes, the peak domestic
demand is considered to be the greater of--
(a) Maximum day demand, i.e., 2.5 times the required daily demand.
(b) The fire flow plus fifty percent of the required daily demand.
(14) Fire flow. The required number of L/min (gal/min) at a specified pressure at the
site of the fire for a specified period of time.
(15) Fire demand. The required rate of flow of water in L/min (gal/min) during a
specified fire period. Fire demand includes fire flow plus 50 percent of the required daily
demand and, in addition, any industrial or other demand that cannot be reduced during a fire
period. The residual pressure is specified for either the fire flow or essential industrial demand,
whichever is higher. Fire demand must include flow required for automatic sprinkler and
standpipe operation, as well as direct hydrant flow demand, when the sprinklers are served
directly by the water supply system.