Introduction

A Tank node in an urban Deveoper Scenario is used to store water collected from a roof surface. This stored water can be accessed to supply e.g. non-potable water demands.

Once linked, a rainwater tank can be a supply to all water end-use demands within a household.

The Tank node allows for the inflow of rainwater from a roof as well as the provision of trickle top-up from the mains supply, triggered to start and stop at a user-specified tank level.

Restrictions

There are restrictions on which node inputs and outputs you can connect together. See Urban Developer node connection rules.

The Tank node is available for Urban Scenarios only.

Contents

Node Dependencies

Inflow: Inflow to a Tank node in an Urban Developer Scenario in Source is from a Roof node.
Top-up: Tank top-up is controlled by a parameter in the tank property editor (see below). The top-up function takes water from the mains supply.

Node Outputs

Demand: The tank volume extracted by a Water Use node per unit time.
Link type: Demand

Node Properties

The tank parameters must be configured to represent the total number of dwellings in downstream Average or Behavioural Water Use nodes. For example, 4 houses with 10 m³ of tank volume each would need to be attached to a single tank node with 40 m³ total volume.

Properties of the Tank node are described in the table below and illustrated in Figure 1, with details of the Tank specifications in the Urban Developer Plugin SRG.

Figure 1. Urban Developer storage tank definition.

where

V_Detention is the Detention Storage Volume (m³);

V_Retention is the Retention Storage Volume (m³);

V_Dead is the Dead Storage Volume (m³);

h_off-taker is the height of the supply off-take obvert from the base of the tank (m);

h_retention is the height of the retention storage volume (m);

h_detention is the height of the detention storage volume (m);

h_tank is the height of the storage tank (m);

h_{TT On} is the height of the trickle top-up on trigger (m); and

h_{TT Off} is the height of the trickle top-up off trigger (m).

Property	Description	Units	Default Value	Recommended Range	Constraints
Dimensions
Cross-sectional area	Defines the cross-sectional area of the tank base.	m²	2.5	NA	>= 0
Height	Defines the total height of the tank. Includes detention and dead zone height	m	2	NA	>= 0
Height of off-take invert	Defines the height of the offtake pipe on the tank; the offtake pipe supplies demands from the tank. The invert level of the offtake is the height of the lowest point of the pipe above the tank base. Once the tank is filled above the offtake invert level, the water depth in the tank will never fall below this level. Demand off-take occurs from the base of the tank just above the anaerobic or "dead" zone; a tank should therefore have a minimum "dead zone" depth of 0.1 m to allow for accumulation of sediment and other material. Water will never be drawn from the "dead zone".	m	0.1	[0, 2]	>= 0
Initial water depth	Defines the initial depth of water in the tank at the start of the model run.	m	0.1	[0, 1000]	>= 0
Overflow Configuration
Detention volume depth	Defines the detention (storage) volume depth of the tank. The detention volume depth is the depth from above the overflow outlet invert to below the tank spill/top of the tank Detention volumes are used as buffers to decrease output flow rates in situations of high input flow. If the tank has no detention storage, set the detention volume depth equal to the overflow outlet diameter.	m	0.1	NA	[0, 2]
Orifice diameter	Defines the diameter of the overflow orifice, located at the base of the detention storage.	mm	100	[10, 320]	[1, 1000]
Orifice discharge coefficient	Discharge coefficient used in the evaluation of the orifice flow equation.	NA	0.86	NA	NA
External top up
Enable external top-up	If enabled, allows for the tank to be topped-up with mains water so that the tank always maintains a user-specified water level. When you enable external top-up, Urban Developer handles the mains connection internally.	NA	Disabled	NA	NA
Top-up rate	Defines the rate of mains water top-up in litres per second.	L/s	250	NA	>= 0
Top-up triggered on	Defines the depth above the tank base at which the tank will start to top up. This depth must be greater than the height of the off-take.	m	0.2	NA	>= 0
Top-up triggered off	Defines the depth above the tank base at which the tank will stop automatically topping up. This depth must be greater than the Top-up triggered-on depth.	m	0.3	NA	> Top-up triggered on
First Flush System
Enable first flush system	If enabled, changes the tank inflow behaviour so that a user-specified volume of water will bypass the tank before inflow to the tank occurs.	NA	Disabled	NA	NA
First Flush Volume	Specifies the volume of water the first-flush device diverts.	m³	0.015	[0, 100]	>= 0
First Flush Outlet flow rate	Specifies the outflow rate to the selected discharge outlet.	m³/s	0.01	NA	>= 0
Discharges Connection	Specifies the tank outlet that first-flush outflow is discharged through. Detention outflow specifies that the first flush volume discharges via a connection to the detention outflow pipe. Spill specifies that the first flush volume discharges via spilling from the tank.	NA	NA	NA	NA

User Interface

The Tank node is configured via the node Feature Editor. Node properties are accessed through 4 levels:

Property	Interface
1 Tank Dimensions		2 External top-up
3 First Flush behaviour		4 Overflow configuration

Acknowledgements

This material has been adapted from:

eWater Cooperative Research Centre (2011) Urban Developer Product Specification: Storage Tank Routing v0.4. eWater Cooperative Research Centre, Canberra. 23 June 2011.

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