This clarification enables water authorities to provide greater certainty to industry on the available reticulated water supply residual pressure under 95th percentile demand conditions.
Background
Sub-clauses (a), (b), (c) and (d) of Clause 4.2.7.1.2 of AS 2419.1:2021 introduced new requirements for the determination of ‘minimum design residual pressure’ used as the basis for designing a fire hydrant system. These sub-clauses require that the minimum design residual pressure is determined, in order of availability, by the water authorities (network utility operators). Water authorities provide pressure and flow Information reports to enable practitioners (such as hydrant system designers) calculate the available reticulated water supply residual pressure under 95th percentile demand conditions.
Sub-clauses (a) and (b) of Clause 4.2.7.1.2 have complex terms and are not explicitly defined, either within the standard, the ³Ô¹ÏÍøÕ¾ Construction Code or other related standards. This lack of clarity has resulted in challenges with interpretation and application, leading to confusion and uncertainty for practitioners. This situation is further compounded when there are different circumstances and considerations that apply in regional, rural and urban water networks.
Clarification
The VBA, in consultation with Victorian water authorities and industry stakeholders, confirms the clarifications below apply to sub-clauses (a) and (b) of Clause 4.2.7.1.2 of AS 2419.1:2021. These clarifications will be adopted by Victorian water authorities when they provide pressure and flow Information reports to practitioners who design fire hydrant systems.
Sub-clauses of AS 2419.1:2021 | Clarification |
|---|---|
Clause 4.2.7.1.2 (a) A network utility operator’s water supply network hydraulic model that has been calibrated for fire flow friction losses, background network demands and local network boundary conditions. The network hydraulic model shall accurately calculate the available reticulated water supply residual pressures under 95th percentile demand conditions together with the total firefighting flows to the connection point of the fire hydrant system at the reticulated water supply. | Model calibration involves matching simulation outputs to observed field data by adjusting the model. This includes the adjustment of roughness coefficients to simulate friction losses observed under peak demand conditions. Calibration for ‘fire flow friction losses’ is not achievable by the network utility operator. In the hydraulic model under 95th percentile demand conditions, incremental flows are induced from the supply pipe outside the subject development up to the maximum achievable flow or as limited by the network utility operator. The flows and corresponding residual pressures are presented on a pressure and flow statement issued to the designer. The network utility operator will determine whether the model output is suitable for its intended purpose. |
Clause 4.2.7.1.2 (b) A network utility operator’s uncalibrated water supply network hydraulic model supported by suitable field tests, to verify and adjust the hydraulic model’s reticulation mains fire flow friction losses to the connection point of the fire hydrant system at the reticulated water supply. | An uncalibrated model’s simulation output has not been calibrated to match observed field data but may have undergone a level of validation. It is however deemed suitable by the network utility operator for its intended purpose. In the hydraulic model under 95th percentile demand conditions, incremental flows are induced from the supply pipe outside the subject development up to the maximum achievable flow or as limited by the network utility operator. The flows and corresponding residual pressures are presented on a pressure and flow statement issued to the designer. It may be that the network utility operator requires the data to be verified using a method approved by the network utility operator. No further model adjustments are required and ‘fire flow friction losses’ are not modelled by the network utility operator. |
No clarifications are provided for sub-clauses (c) and (d) of Clause 4.2.7.1.2 of AS 2419.1:2021.
