Rain barrels

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Simple rain barrel with a hose attached to use the water

This article is about outdoor, residential systems. For larger, multi-residential or commercial integrated systems, see Rainwater harvesting

Overview

Rain barrels are an above ground form of rainwater harvestingThe practice of intercepting, conveying and storing rainwater for future use. Captured rainwater is typically used for outdoor non-potable water uses such as irrigation, or in the building to flush toilets., typically used in residential settings. The precipitationAny form of rain or snow. flows from the roof, to the guttering and down the downspout before being diverted to the rain barrel for storage.

Rain barrels are an ideal technology for:

  • Individual homes, where the owners can make good use of the water to irrigate a garden
  • Retrofitting single family home neighborhoods
  • Areas with mandatory downspout disconnection programs

The fundamental components of a rain barrel system are:

  • A catchmentThe land draining to a single reference point (usually a structural BMP); similar to a subwatershed, but on a smaller scale. where the rain lands, this will usually be a rooftop,
  • guttering and downspouts to channel the rainwater,
  • screens or filters to remove leaves and other large debris,
  • a rain barrel to hold the collected water,

Additional components may include:

  • a tap or faucet fitted to the barrel,
  • a hosepipe or other irrigationHuman application of water to agricultural or recreational land for watering purposes. City of Toronto Wet Weather Flow Management November 2006 47 system.

Planning Considerations

Leaf screens can be included along the eaves-troughs (above) or integrated with the downspout (below)
The screen on this rain barrel prevents mosquitoes from entering and screens leaves from the water.

Watershed scale

Traditional rain barrels require a high degree of owner compliance to perform as a reliable stormwater management control strategy at watershed scale. To overcome this limitation, electronically monitored and controlled rain barrels are a new adaptation on the market in Ontario[1]. This system forecasts rain and automatically discharges the contents of the rain barrel to a designated infiltration area of the property in advance of the storm.

Site Scale

Place in the Treatment Train In most cases the catchmentThe land draining to a single reference point (usually a structural BMP); similar to a subwatershed, but on a smaller scale. area will be the roof of the building and the rain barrel will be the first interceptionThe interception, storage and eventual evaporation of rainfall from vegetation canopies. of water from the downspout. Planning questions:

  • How many downspouts does the roof have?
  • Will more than one barrel be required?
  • Do the downspouts require reconfiguration?

It is recommended that an overflow strategy be part of designing a rain barrel system. Excess water should be directed away from the property foundations. Suitable discharge points for overflow include: a rain garden, a french drain, or the base of a tree.

CisternTank used to store rainwater (typically roof runoff) for later use.

Expansion caused by freezing water will damage the barrel. The easiest way to prevent this damage is to drain and disconnect the system in advance of freezing temperatures[2].

Design

Filter

The water in the barrel will remain fresher for use if leaf litter and other debris excluded. Screens can be installed on the eavestroughs, in the downspout, or at the top of the cisternTank used to store rainwater (typically roof runoff) for later use.. These types of screens are not designed to capture small particles and chemical pollutants. However, this fine material is usually first to wash off surfaces at the start of the storm. A first flushThe delivery of a disproportionately large load of pollutants during the early part of storms due to the rapid runoff of accumulated pollutants. The first flush of runoff has been defined several ways (e.g., 10 mm per impervious area).Initial pulse of stormwater runoff which picks up the pollutants that have settled on surfaces during the dry period. The first flush contains the highest pollutant concentrations. diverter is a simple, automated, mechanical device which prevents this first 'dirtier' part of the stormwater from being stored. Screens, filters and diverters should be in easily accessible locations, so that they can be inspected and cleared of debris periodically.

Sizing Barrels

Roof catchmentThe land draining to a single reference point (usually a structural BMP); similar to a subwatershed, but on a smaller scale. area can be estimated using one of many online digital maps. e.g. Distance can be measured on Google maps by right clicking on the desired start point.
1 mm of rain landing on 1 m2 of roof top produces 1 litre of water to store.
So a 5 mm storm on a 75 m2 roof would require 375 L of storage volume.
Rain barrels or cisternsTank used to store rainwater (typically roof runoff) for later use. are readily available in pre-formed plastic up to around 500L.
Alternatives include:

  • modular systems to increase total storage capacity,
  • slim designs to fit small spaces,
  • aesthetic designs for high profile locations,

Many people choose to reuse or recycle a container as a rain barrel or cisternTank used to store rainwater (typically roof runoff) for later use.. Re-purposed containers should be screened to prevent mosquitoes from breeding, and should be opaque to prevent algae from growing.

Performance

Starting after TRIECA (end March) members of STEP will be undertaking a literature review on the performance of our most popular BMPs. The results will be combined with the information we have to date from the development of the Treatment Train Tool and agreed performance metrics established. Until then, please feel free to continue to ask questions via email or the feedback box below.

Water Quantity

The use of rain barrels (190L) across a watershed of 100 residential units has been modelled for a number of U.S. cities[3]. In Philadelphia and Milwaukee (reflecting the most similar climates to Southern Ontario) the use of rain barrels for irrigationHuman application of water to agricultural or recreational land for watering purposes. City of Toronto Wet Weather Flow Management November 2006 47 only, provided an annual stormwater reduction of less than 2%.

Water Quality

The Ontario building code (OBC) requires only that water collected from rooftops be "free of solids" for irrigationHuman application of water to agricultural or recreational land for watering purposes. City of Toronto Wet Weather Flow Management November 2006 47 use in an external system such as a rain barrel. There is a draft of CSA B805 draft currently under review. The scope of the document includes single family dwellings. But the guide is still under review and may not account for rain barrel systems when officially published. (comments made in reference to draft v. 2, on 1st June 2017). Research in warm climates (Texas and Greece) has demonstrated that first flushThe delivery of a disproportionately large load of pollutants during the early part of storms due to the rapid runoff of accumulated pollutants. The first flush of runoff has been defined several ways (e.g., 10 mm per impervious area).Initial pulse of stormwater runoff which picks up the pollutants that have settled on surfaces during the dry period. The first flush contains the highest pollutant concentrations. diverters improve the chemical characteristics of the harvested rainwater[4][5]. However, the use of diverters does not prevent the development of pathogens in stored water.

Costs

Many municipalities run schemes to provide homeowners with subsidized barrels. In some places barrels can be purchased from around $50. See list below. Additional items such as filters, screens or hoses may cost extra. Hardware stores carry a wider range or products to suit all kinds of space constraints, aesthetic concerns, or budgets. Outdoor barrels for the residential market can cost up to $300, these have larger capacity and smart sensors.

Incentives and Credits

Ontario

See Also

External Links

Proprietary Systems

In our effort to make this guide as functional as possible, we have decided to include proprietary systems and links to manufacturers websites.
Inclusion of such links does not constitute endorsement by the Sustainable Technologies Evaluation Program.
Lists are ordered alphabetically; link updates are welcomed using the form below.