High simultaneous demand (public areas)
Public buildings, schools, swimming pools, campsites, etc. use the formula:
Number of time flow valves: (X) per installation branch
Base flow rate: (Q min. L/sec.): minimum flow rate per outlet, used as a base for calculation.
The base flow rates for time flow mixers/taps are mentioned in the catalogue Water Controls for Public and Commercial Places and in tables 1 and 2 under the option Recommendations for sizing horizontal final pipework.
The base flow rate is always shown as dynamic pressure.
Gross flow rate
Sum of base flow rates of different time flow taps/mixers on the same branch.
Time flow flush valves
Follow the recommendations in Table 1 under the option Recommendations for sizing horizontal final pipework.
(Y) coefficient to apply to gross flow rate, depending on the number of installed valves (X), to simulate the number of valves operating simultaneously.
This coefficient will vary according to the frequency of use of the sanitary facilities.
(Q) gross flow rate x simultaneous coefficient (Y). In principal, flow rates are not cumulative, except for flush valves.
Pressure under flow at a single point in the installation.
For each time flow valve (see table 1 of the option Recommendations for sizing horizontal final pipework).
Maximum pressure for time flow valves to operate: 10 bar.
Recommended pressure range: 1 - 5 bar
Recommended pressure on each floor: 3 bar.Residual dynamic pressure: pressure available at the valve inlet = total pressure - pressure drop.
Average or low demand
The formula (DTU 60-11) is applied
High simultaneous demand at peak periods
Changing rooms, sports stadia, barracks, boarding schools, swimming pools, campsites, etc: use the coefficient Y = 0.6 or 0.7
Pressure with no flow at a single point in the installation.
Static pressure at the water meter.