Physical verification of household rainwater tank systems
5.2.3 rainwater tank installation audit protocol
{ Catchment – installed to receive rainfall from a minimum of 50% of total roof area or 100 m2 (whichever is the lesser).
{
{ Connection to – (1) toilet cistern/s and washing machine cold water taps (other than those connected to a greywater treatment plant or alternative water substitution measure); and (2) an external use.
• Water quality protection:
{
{ Prevention of contaminants from entering rainwater tank – (1) screened downpipe rainhead having a screen mesh 4–6 mm to prevent leaves from entering downpipe; and (2) discarding a minimum of 20 litres of first flush runoff where rainwater is connected to showers, wash basins, kitchen or hot water services.
{
{ Prevention of mosquito breeding and vermin entering the rainwater tank – (1) either mosquito-proof screens (suitable material and not coarser than 1 mm aperture mesh); or flap valves at every opening of tank; and (2) a vermin trap; or (3) in case of wet systems, mosquito-proofing in accordance with Standard HB230 for rainwater tank installation and design.
{
{ Continuous supply of supplementary water to internal fixtures from the reticulated town water supply – by either (1) an automatic switching device; or (2) a trickle top-up system.
{
{ Prevention of contamination of the reticulated town water supply from the rainwater tank – a backflow prevention device is installed.
5.2.3 rainwater tank installation audit protocol
This chapter focuses on a study undertaken as part of the Urban Water Security Research Alliance (UWSRA, www.urbanwateralliance.org.au) project on decentralised systems, which, inter alia, aimed at understanding the effectiveness of achieving the mandated 70 kL/hh/yr water saving target specified under the SEQ Water Strategy (2010) (Queensland Water Commission, 2010). Whilst other parts of the project considered demographic and behavioural factors influencing water savings, this chapter relates to that part of the study which considered physical installation factors.
The audit protocol initially developed for the Sydney BASIX compliance assessment (Sydney Water, 2009) was adapted to accommodate the requirements of the SEQ-specific QDC MP 4.2 water savings target. This protocol formed the basis of the household inspection protocol undertaken in SEQ in 2011.
The final framework was the result of a number of iterations based on inputs obtained from a number of key stakeholders, including the water service provider, after piloting the survey for ten households. The final protocol covers the following aspects (Figure 5.1):
• characteristics of individual dwellings (e.g., dwelling type, total roof area, property dimensions);
• installation of water efficient appliances and fixtures (e.g., showerheads, washing machine);
• information on the rainwater tank systems (e.g., tank volume, roof area connected, type of rainwater conveyance system – wet or dry, pump size);
• internal connections for rainwater supply (e.g., plumbing connections to/from the tank); and
• other water related features on the property (e.g., swimming pool, spa).
For each of these components, a number of detailed parameters was identified and a measurement method determined (Table 5.1). The protocol has been designed to be inclusive of water quality aspects as well as quantity. However, in the application of the protocol to the case study area, the focus of the assessment was on water quantity aspects because the specific research question related to potable water savings.
Figure 5.1 Physical components comprising the rainwater tank installation compliance audit protocol.
table 5.1 Tank installation compliance audit protocol for SEQ.
parameter measurement method
characteristics of Individual dwelling
Dwelling type Visual inspection. The dwelling types are: detached house; semi-detached house; townhouse; studio/
granny flat; or other (described).
Total roof and garden area The total roof area for each site to be determined using aerial photography, where available, to mark out and measure the garden and roof catchment areas.
Number of bedrooms Visual inspection and count of all of the bedrooms in the house.
water efficient Appliances and Fixtures Number of showers and showerheads – check/
calibrate the flow rate in litres per minute for each showerhead
The number of showers and shower heads determined through inspection of each bathroom and asking the owner. Occasionally there are showers located in the garden. For each shower head, determine the flow rate using a stopwatch and measuring jug. Record the time required to fill a 3 L measuring jug.
Number of washing machines, including type, brand, model and load size (kg) for each machine
The manufacturer’s plate has the information required.
Are any of the washing machines connected to the rainwater tank? If yes,
Is it connected to the cold tap? Specify other washing machine cold tap
Configuration (if any)
Two effective methods of assessment. The first is turning on the washing machine and checking whether the rainwater pump is activated. The second is to turn off the rainwater supply while leaving the mains water supply on and check whether water flows into the washing machine.
Also, some washing machines are plumbed with a separate rainwater cold tap.
table 5.1 Tank installation compliance audit protocol for SEQ (Continued).
parameter measurement method
Number of toilets – check /calibrate the flush volumes for half and full flushes
The number of toilets determined through inspection and asking the owner. To determine the flush volumes of the toilet, turn off the water leading into the cistern, noting the water level and then flushing the toilet. A measuring jug is then used to fill the cistern back up to the previous level and the water required to do this is noted.
Is/are the toilet(s) connected to the rainwater tank?
The same method used as for testing the connection of the washing machine. Either the toilet will be flushed and the system examined for rainwater pumping, or the rainwater supply will be switched off and the toilet checked to see if mains water fills the cistern.
Information on rainwater tanks
Number of rainwater tanks Inspection and ask the owner, check for underground/hidden tanks.
For each tank, record the type and shape of tank
Visual inspection – either underground, above ground or bladder style.
Tank dimensions (height × length × width) Measure in millimetres using a tape measure.
Underground tanks cannot be measured in this way and the assessor must rely on the manufacturer’s certificate.
Tank diameter Measured using a tape measure.
Tank volume (claimed) If the tank has a manufacture’s volume stamp on it, record this.
Tank materials (e.g., Polyethylene, galvanised steel, stainless steel, concrete)
Determine by visual inspection. Unless convincing evidence can be given by the owner (such as a receipt), the material of underground tanks will not be able to be determined.
Actual tank volume in storage Determine by noting the shape, measuring the height of the off-take, cut-off switch, overflow and total height of the tank. It may not be possible to measure the float level where there is a trickle top-up system or the water level threshold used to activate the automatic switching to the reticulated water supply. These are located in the tank and accessing them is a safety issue. The measurements that are able to be obtained will give valuable information on the effective tank volume and any dead spaces in the tank.
Size of roof catchment area connected to the tank
If the system is uncharged (that is, the downpipe drains completely into the tank, with no water held in the pipe – Figure 5.2a), it is relatively clear which (Continued)
table 5.1 Tank installation compliance audit protocol for SEQ (Continued).
parameter measurement method
downpipes feed rainwater to the tank. Once this has been determined, examination of the roof shows which area drains to the downpipe. Where a section of roof is drained by two downpipes, one draining to the tank and one not, the slope of the gutter will be used to determine which part of the roof drains to which downpipe and from there the tank.
Charged systems, (where the downpipes feeding the tanks are full of water – Figure 5.2b), can be checked by tapping the pipes to hear if they are full. After that, the same method outlined above can be used to determine the roof catchment area connected to tank.
Mark this information on a satellite image or aerial photographs of the house to determine the area.
Rainwater pump brand and model number Determine from the manufacturer’s plate on the pump. Where plates are in an awkward position to access, damaged or lack required data, pump parameters can be determined from manufacturer’s specifications.
Minimum level setting in rainwater tank (in litres) This will be either the level of the cut-off switch or the off-take height (see Figure 5.3).
Is there an automatic switching device or a trickle top-up system providing supplementary water from the reticulated town water supply?
Note type of potable top-up system (description and model). The difference between trickle top-up and automatic switching devices can be determined by a simple examination of the presence of a switching system on the pump or a mains top-up valve on the top of the tank. The switching device has an in-tank water level sensor that causes the switching valve to change over to mains water based on the water level in tank.
That is, no mains water enters the tank. The trickle top-up system operates through a float valve that allows mains water to recharge the tank between two defined water levels.
Is there any backflow prevention system? Backflow prevention systems are located either immediately upstream of the mains input into a switching device, or on the mains meter. They are quite distinctive fittings.
Is there any screened downpipe rainhead, having screen mesh 4–6 mm and designed to prevent leaves from entering each downpipe?
Rainheads are easy to identify visually. Use a measuring tape to measure the screen mesh.
table 5.1 Tank installation compliance audit protocol for SEQ (Continued).
parameter measurement method
Is there any first flush device installed. If yes, what is the volume capacity of the device?
First flush devices are easily recognisable visually.
Volume of first flush devices can be estimated either by measuring the length and diameter of the structure and calculating the volume, or by taking a photo, writing down the product name and comparing with manufacturers specifications.
Is there a mosquito-proof screen of brass, copper, aluminium or stainless steel gauze not coarser than 1 mm aperture mesh or flap valves at every opening of the rainwater tank?
This can be assessed through visual inspection.
Is there a vermin trap, wet system used to harvest rainwater, mosquito proofing in accordance with Standard HB230?
Visual assessment.
Are the rainwater tank’s openings constructed to prevent ingress of surface stormwater and groundwater?
This can only be assessed to a limited degree for underground tanks. Where possible, assess all water entry points into the tank to ensure there is no potential contamination from groundwater or surface water. This may include assessment of invert levels, quality of fittings and quality of lid design and construction.
If multiple tanks exist, are they connected to each other?
Visual inspection of connections, usually at the base of tanks.
Number of external taps connected to each rainwater tank
Assessed by turning on the tap and checking for flow from the rainwater pump.
Is the rainwater tank connected to the hot water system?
This is done by turning off the rainwater tank system and operating a hot water tap. No flow indicates a rainwater source.
Is the rainwater used for drinking water and other household supply?
Turn off the rainwater tank system and operate a kitchen tap, laundry tap, bathroom tap, and so on for flow. No flow indicates a rainwater source.
Is the overflow connected to the stormwater drain?
If yes, is there a physical air break or non-return valve on the rainwater tank overflow outlet before connecting to the stormwater drainage system?
Visual assessment. From NSW experience, this has been almost impossible to determine without either digging up the pipes or running enough water through the rainwater overflow to discharge into the stormwater drain.
condition of tanks, gutters and pumps What is the rainwater tank condition (good, satisfactory or poor)
Visual inspection including: leaks from the tank;
rust or corrosion; and quality of foundation Rainwater tank installation year Assessed by questioning the owner. There is
rarely an installation date placed on the tank.
(Continued)
TANK TANK
(a) (b)
Figure 5.2 Schematic of (a) uncharged and (b) charged rainwater conveyance systems from roof to tank.