Conserving Water with a Rainwater Cistern Tank and Gravity Watering System

Reader Contribution by Mary Lou Shaw
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Water conservation seems increasingly important to my husband and me as we watch large Ohio farmers use water from aquifers to irrigate their fields. Instead of depleting aquifers, we’ve chosen to both conserve water and to water our garden during dry periods. To accomplish this, we put in a rainwater cistern tank last autumn. The project continued this spring by installing two elevated watering tanks for our garden’s gravity watering system.

This project began by hiring a friend with a back-hoe to dig a premeasured hole in the chicken yard, adjacent to the garden. A 2,500 gallon cement cistern was then purchased from a local septic tank company who delivered and installed it in two parts—bottom and top. This cost a total of $1552. A heavy plastic tank could also have been used.

In addition to the standard opening on top, it has an opening high on one side where water enters the cistern. Opposite this entrance is a hole where water exits when it nears the top of the cistern. This surplus water travels through a porous tile so water can be furnished to dry soil as it makes its way under the garden, through the pasture and into the creek in the lower meadow.

The rainwater cistern tank was filled with rain water by

diverting water from adjacent roof-tops. The downspouts on the chicken house, garage, outhouse and house were attached to solid, four-inch tiles. Using solid tiles assures us that the tiles won’t be obstructed with tree roots. A rented trencher created the furrows to bury these tiles which were joined before entering the cistern.

The cistern was installed last autumn so it could be filled with this spring’s rain. We are able to check the water level in the cistern by putting a premeasured board into the tank’s top opening. I find it amazing that less than two inches of rain can fill such a large tank.

We began to assemble what was needed for the garden’s gravity watering system last winter. Craigslist provided us with two food-grade, plastic storage tanks. Each tank holds 250 gallons of rain water and is supported six feet off the ground by a base constructed of treated wood. We would have liked to avoid using treated wood in proximity to the garden, but this would have necessitated pouring a cement base for each vertical post. In truth, once spring milking began, there wasn’t much time for other projects.

When the two storage tanks were in position and the cistern filled with rain water, we submerged a portable electric pump through the cistern’s top opening. This pumped water against gravity through a two-inch plastic pipe to each storage tank. The cistern then filled again with the next rain.

You might want to consider using a wind turbine as a pump for your water conserving system. Again, the multiple spring tasks on our homestead made using electricity rather than wind much more feasible. When we need to save time on projects, we look gratefully to our solar panels for the energy needed.

This summer, the set-up for our gravity watering system did not get very sophisticated. The garden is quite heavily mulched and we were pleased to get adequate rains until mid-August. A humble hose therefore completed our irrigation system. We have grander plans for the next garden season, however!

Here is what we envision. Each elevated storage tank has a two-inch opening at the base where we will attach
an adaptor for a two-inch PVC pipe. That diameter pipe will gradually be narrowed to maintain pressure as the water travels down to the plants. For example, the pipe’s diameter will be reduced by one-half inch increments from two inches to one-half inch. This should maintain enough pressure to keep water flowing for one 25 foot garden row at a time.

The plastic pipe for each row will have holes drilled in them for watering. Again, to maintain pressure, the holes will begin smaller at the beginning of each row and gradually enlarge down the length of the pipe.

We had originally thought we could carry a horizontal pipe from one row to the next, providing irrigation pipe only to the rows being watered. However, as we watched our leggy tomatoes and hardy vine plants spread out this year, we realize their summer tangles will make moving and positioning the pipe difficult. We think there might be a big advantage to arranging and leaving the porous PVC pipe in place when plants are seedlings. We can then reclaim the pipe during the autumn garden clean-up and hang them on the garden fence for storage.

To summarize our water saving garden project this far, we can say that the rainwater cistern tank has been completed and works well. The gravity-fed irrigation system is coming along with the two elevated tanks in place and easy to fill. Next year we will work on the distribution system with plastic pipes going to our favorite plants. As rains become less predictable, we hope to get the entire garden set up for rain water irrigation.

Do some of you wonder what became of all the soil removed for the 2,500 gallon cistern? Well, that became the foundation for a smokehouse—but that story can wait for the next blog!

Mary Lou Shaw and her husband live on a 13 acre homestead in Ohio where they grow almost all the food they eat. Mary Lou’s book, “Growing Local Food,” is available through Mother Earth News.

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