Caribbean Water Cisterns

Grenada roof with guttering.

Grenada roof with guttering.
Photo Credit : Caribbean Land & Property

The cistern system utilised in the Caribbean is one of the most innovative and cost effective ways of capturing and storing large quantities of fresh rain water.

For the everyday Caribbean home owners, the cistern is merely an addition to the house. But, in fact, when we examine the secret life of a cistern – its appreciation is deepened and this multifaceted, pivotal part of every Caribbean homes’s functionality becomes simply – a blessing! Many islands experience water shortages during periods of low rainfall or unexpected water interruptions from the local water boards and then – old faithful, heroically, steps in and saves the day or even weeks!

Let’s examine the well known but, often over looked, roles a cistern system takes on while quietly adding that little bit of comfort to Caribbean living!  A cistern system has four major components:

· Catchment area
· Conveyance system
· Storage device
· Distribution system

BVI Villa with large roof catchment Photo Credit : Caribbean Land and Property

BVI Villa with large roof catchment
Photo Credit : Caribbean Land & Property

Catchment Area
The catchment area is generally a rooftop or pavement. Larger catchment areas are more commonly made with concrete or other pavements. These are used for systems large enough to service a community or commercial properties (Hotels, hospitals, schools etc.)

Conveyance System
The conveyance system is made up of a network of gutters and pipes designed to move the water from the catchment area and into the storage device. This system uses connections to one or more down pipes connected to the gutters. A unique part of this system is a first flush device, a part of the downpipe configured to divert the roof debris from entering the storage tank. Because this method can’t catch everything, screens are often used to help keep leaves and other debris out of our storage devices.

Some systems have baffle tanks which use a two-screen design. The first has larger holes than the second, so finer particles are kept out. If you are going to use rainwater for household uses such as washing, or cooking, special filtration systems can be added to remove contaminants down to the microbial level. Water with less contaminants is also helpful in making interior plumbing, such as pipes and water heaters last longer. Signs of rust on water heaters or pipes can be a sign that they will need to be replaces, which can be a costly process.

Storage Device
Storage tanks can be above ground, underground, or partially underground. We can find them built using a variety of materials from ferrocement, bricks and blocks, concrete, metal, plastic, wood, and fiberglass.

Protective Gutter Mess

Protective Gutter Mess

Within the storage device, pipes are configured near the bottom of the tank to force the stored water, which is generally better quality than fresh rainwater, to the top for current use.

This same pipe configuration prevents the outflow from disturbing any sediment that might have accumulated at the bottom of the tank. To reduce the risk of having the system collapse during a rainstorm, an overflow must be installed. This can be done using a standard arrangement, inflow exclusion, desludging bottom exit, or top cleaning siphonic action depending on the configuration of our system.

Distribution System
The distribution system is just as varied as the other components. It can be pressurized using a pump or using head pressure. Special filtration systems can also be added to remove even microbes.

Although the basic parts of a cistern system are relatively simple, there are many ways they can be adapted for use in specific settings. Whatever system set-up used, rain-water catchment is an environmentally conscious way to help solve the water issues in the Caribbean. See, and you always thought of it as just “a cistern” – the injustice!

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