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Rainwater Harvesting at the Garden Home Retreat

The cistern being built.

Nestled behind the cottage in a flat area destined to be the croquet lawn I've buried a hidden treasure. Two feet below the surface of the ground I'm hording a very precious commodity – rain water. Anyone who gardens knows how much water it takes to keep plants growing and with more than 700 feet of garden space at the Retreat, I need lots of water.

Unfortunately the site is off the city water supply and wells are the only source for both drinking water and irrigation. While the supply of well water is abundant, it requires treatment to be safe for household use. So I decided to check into rain water harvesting as a way to reduce the amount of treated well water required for irrigation. An added benefit is that the rain water is significantly better for the plants.

To make sure I selected the right system for collecting and storing the water I enlisted the help of Shawn Hatley at Brae Rainwater Technology. After visiting the site Shawn told me that over the course of a typical year I may be able to capture as much as a half a million gallons of water from the various buildings on the property. That's like the size of 2 Olympic swimming pools!

Good to Know: Acid Rain
If acid rain is a problem in your area, add a piece of cement or some lime to your water storage tank. This will help neutralize the acidity in the water.

Shawn developed a system for the site that has several components. When rain falls on the roofs of the buildings, it is collected in gutters and channeled through downspouts. Pipes connected to the downspouts funnel the water through a filter that removes debris and then delivers it to a 6000 gallon, underground cistern for temporary storage. The water is pumped to an above ground wooden storage tank high above the gardens so it can be gravity-fed to irrigate the beds.

The cistern is unique because it is built with small collapsible units that look like milk crates. These units are made of 100% recycled plastic and can hold about 32 gallons each. The pieces snap together easily to create a variety of different configurations. The advantage of being a modular cistern is that it can be modified to fit into different underground spaces. Let's say you have a high water table. The pieces can be fit together to create a shallow cistern. Or if you have a very compact space in your backyard, but still want big storage capacity, you could go deep with a tall, narrow cistern.

This is a pretty ambitious undertaking, but there are options for smaller gardens as well. In fact, for just a few hundred dollars you can install a few connectors and an above ground storage tank. Learn more at

  1. Matrix D Rain Tank Unit

    One of the tank units used to build the cistern.

    The cistern is built by stacking these boxes together. Although they appear delicate, they are incredibly strong. Cisterns made of this material will hold up even when buried under parking lots and driveways. The boxes are flexible, so to hold water the cistern is wrapped in a liner like a birthday present.

  2. Burying the Cistern

    The cistern liner being laid on top of the protective liner.

    Here you can see the hole for the cistern. The hole is lined with protective material to shield the cistern from sharp objects in the soil. Next the cistern liner is laid out and the modular units are stacked together on top of it. Once the cistern is built, the liner is pulled up and over like wrapping paper. Then the hole is backfilled and we are in business!