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A tank is a type of storage used in domestic, commercial and/or industrial settings

Introduction

A Tank node in an urban Deveoper Scenario is used to store water collected from surface runoff or sources such as greywater or blackwater waste streams. Once stored the water can be released in a controlled manner, and/or used to supply water demands.
There is a trend towards installing domestic rainwater tanks in urban areas to capture roof runoff and supply a roof surface. This stored water can be accessed to supply e.g. non-potable water demands. The benefits of using water sourced from a rainwater tank include:• reduced reliance on potable water supply, thus deferring potable water system upgrade or expansion and increasing the security of supply from existing water sources;
• stormwater retention/detention;
• urban water quality improvement via retention and diversion of stormwater to the sewer and garden areas, thus reducing the volume of stormwater pollutants discharging to the catchment watercourses; and
• protection of urban streams, through reducing the duration of elevated flows.Rainwater tanks are most efficient when the retained water supplies multiple water demands within a household, eg toilet flushing, garden irrigation, filling or topping-up swimming pools, clothes washing and other appropriate non-potable uses.
Tank construction
Rainwater tanks are usually constructed from plastic, or galvanised steel, and are located above-ground adjacent to the sides of a dwelling or building. Where space is limited, tanks can also be installed below-ground, under-floor and in-slab - in these situations, tanks are often constructed from concrete or impermeable plastic membranes.
Restrictions
In many areas health departments do not expressly prohibit rainwater tanks supplying drinking water, however, guidelines typically recommend avoiding drinking rainwater where a reticulated potable supply is available.Multiple tanks
In the current version of Urban Developer, you can connect more than one tank to a supply point; however this model type is not currently supported and may give inaccurate results. If you need to model a multiple-tank installation, the best workaround is to regard the entire installation as a single tank, and adjust initial levels, first-flush volumes etc, accordingly.
Tank (Urban Developer type)
Conceptually, the operation of a rainwater tank is identical to the operation of any tank-based storage infrastructure. The simulation scheme developed for Urban Developer is generic in its applicability to all forms of tank-based storage.
The tank

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.
Inputs
• Inflow: Tank inflow is usually from a roof node (page 116) or other impervious area (page 110).There is no direct input capability for "topping-up" the tank; topup


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Contents

Table of Contents
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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, however in this version, the mains supply usage due to trickle top-up is not tracked in
  • the mains supply
aggregation
  • .
This functionality will be added in future versions of Urban Developer
Outputs
• Supply out

Node Outputs

  • Demand: The tank volume extracted
from
(page 143)
(page 66)PropertyNotesTank dimensions Cross-sectional area (m2)
  • : Demand

Node Properties

• Spill: The volume flowing out of the tank when the detention volume is exceeded.
Link type (page 66): Runoff
• Detention outflow: The flow from the overflow pipe at the invert of the detention volume, during a flood event.
Link type (page 66): Runoff
Restrictions
There are restrictions on which node inputs and outputs you can connect together. See Urban Developer node connection rules (page 102).

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.

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where

VDetention       is the Detention Storage Volume (m³);

VRetention       is the Retention Storage Volume (m³);

VDead            is the Dead Storage Volume (m³);

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

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

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

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

hTT On            is the height of the trickle top-up on trigger (m); and

hTT Off            is the height of the trickle top-up off trigger (m).


PropertyDescriptionUnitsDefault ValueRecommended Range

Constraints

Dimensions

Cross-sectional areaDefines the cross-sectional
or
area of the tank base.m22.5NA>= 0
Height
(m)


Defines the total height of the tank
in m
. Includes detention and dead zone height
.and dead zone height.
m2NA>= 0
Height of off-take
(m)
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.

1m

1 m to allow for accumulation of sediment and other material. Water will never be drawn from the "dead zone".

Default:
m0.1
m Minimum: 0.0 m Maximum: 2.0 m
[0, 2]>= 0
Initial water depth
(m)
Defines the initial depth of water in the tank at the start of the model run.m
Default:
0.1
m Minimum: 0.0 m Maximum: 1000.0 mOverflow outlet and detention storage 
[0, 1000]>= 0

Overflow Configuration

Detention volume depth
(m)


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

; hdet in the diagram.

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
Default:
0.1
m Constraints: ≥ 0 m, ≤ 2.0 mOverflow outlet diameter (mm)Overflow outlet
NA[0, 2]
Orifice diameterDefines the diameter of the overflow orifice, located at the base of the detention storage.
Default: 100 mm Recommended minimum: 10 mm Recommended maximum: 320 mm Constraints: ≥ 1 mm, ≤ 1000 mm
mm100[10, 320][1, 1000]
Orifice discharge coefficientDischarge coefficient used in the evaluation of the orifice flow equation.NA0.86NANA

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.
You do not need to connect a mains water supply node to a tank node to provide inflow for topup; when
When you enable external top-up, Urban Developer handles the mains connection internally.NADisabledNANA
Top-up rate
(L/s)
Defines the rate of mains water top-up in litres per second.L/s250NA>= 0
Top-up triggered on
(m)
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.		m0.2NA>= 0
Top-up triggered off
(m)


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.		m0.3NA> Top-up triggered on

First Flush System

 
Enable first flush systemIf enabled, changes the tank inflow behaviour so that a user-specified volume of water will bypass the tank before inflow to the tank occurs.NADisabledNA
Volume (m3)
NA
First Flush VolumeSpecifies the volume of water the first-flush device diverts.m3
Default:
0.
0 m3 Recommended maximum: 100 m3 Constraints: ≥ 0.0 m3Outlet flow rate (m3/s)
015[0, 100]>= 0
First Flush Outlet flow rateSpecifies the outflow rate to the selected discharge outlet.m3/s0.01NA>= 0
Discharges
to
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.

Other
 Tank bypassIf enabled, all inflows flow directly to the detention outflow.
This allows you to temporarily disconnect a tank without removing it from the model. A bypassed tank still has a small impact on model run-time performance, due to the direct routing of flow from the inflow connection to the detention outflow connection. In testing, simulation time for a disconnected tank is approximately 10% greater than for no tank at all (ie having link with no routing in place of the tank).Image Removed

NANANANA

User Interface

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

PropertyInterface

1 Tank Dimensions 

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2 External top-up

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3 First Flush behaviour

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4 Overflow configuration

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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.