Tuesday, March 2, 2010

Do you want to use grey water for irrigation in San Antonio? Here is an interpretation of the code (with other useful links)

Gray Water is a fantastic way to provide some water for thirsty plants. The good news is that it is legal in San Antonio. Roderick Sanchez, Director of the City of San Antonio Planning and Development Services Department provided an interpretation of the city rules governing residential gray water dated April 20, 2009. I've included a link to a pdf of the interpretation, but for convenience have transcribed the document below:
Interpretation Number: CI2009-002 April 20, 2009
Title: Grey Water Provisions on Residential Applications.

Code/Edition: 2006 Uniform Plumbing Code as amended by COSA

Purpose: To clarify the acceptable provisions regarding the use of grey water on residential applications.

Question: Can I discharge the gray water from a residential washing machine directly onto the ground surface on the exterior of a residence?

Answer: Yes, Gray water may be discharged directly onto the ground surface on the exterior of a residence under the following conditions:

Limited to single family dwellings only.

Irrigated areas must be in a fenced-in area and in control of the occupant of that residence. The area must be limited use and access by residents, pets and foot traffic.

Cannot be used during times of rain.

Irrigation must not create a public health nuisance such as surface ponding.

The irrigated area must support plant growth such as grass, bushes, or be overlaid with a vegetative cover.

The discharge point of the hose shall be kept a minimum of 10 ft from the property lines.

The Director of the Health Department may suspend this practice if he determines that it creates a negative impact on the community health.

Roderick Sanchez, AICP, CBO,
Director and Building Official
Planning and Development Services Department
Joe Barfield provided the above document and link to us. He also included the following resources for anyone considering a gray water system:

Grey Water

Here is Art Ludwig’s page on Laundry to Landscape Greywater System:

There’s a spreadsheet calculator, plus a downloadable parts list / source list. And photos and video.

It is great because he tells you how to ensure that you avoid problems. As in diverting to too small of a tube or if you split into ½ pipes, then you need at least 4 of them to accommodate flow from a 1” outlet from the washing machine. (I made that number up, so don’t use it J. Or to dig a mulch infiltration pit with a “outlet shield” in it for the outlet to freefall into to keep roots from growing in and plugging (and flooding). Plus, have a backflow prevention & a vacuum breaker to avoid siphons. All very cheaply done!

I always have my eye on pool materials put on the curb looking for a discarded 3-way jandy valve… Art sells them for as cheap as you are going to find them anywhere.


Brad Lancaster is the man when it comes to smart water harvesting without a bunch of barrels and pumps. Just small adjustments to your topography and attitude.

You can find his books at the library. I recommend vol.1, but get both if they are available.

He has some great audio that puts things in perspective at harvestingrainwater.com

But most important are his principles:
The Eight Principles of
Successful Water Harvesting

1. Begin with long and thoughtful observation.
Use all your senses to see where the water flows and how. What is working, what is not? Build on what works.

2. Start at the top (highpoint) of your watershed and work your way down.
Water travels downhill, so collect water at your high points for more immediate infiltration and easy gravity-fed distribution. Start at the top where there is less volume and velocity of water.

3. Start small and simple.
Work at the human scale so you can build and repair everything. Many small strategies are far more effective than one big one when you are trying to infiltrate water into the soil.

4. Slow, spread, and infiltrate the flow of water.
Rather than having water run erosively off the land’s surface, encourage it to stick around, “walk” around, and infiltrate into the soil. Slow it, spread it, sink it.

5. Always plan an overflow route, and manage that overflow as a resource.
Always have an overflow route for the water in times of extra heavy rains, and where possible, use the overflow as a resource.

6. Maximize living and organic groundcover.
Create a living sponge so the harvested water is used to create more resources, while the soil’s ability to infiltrate and hold water steadily improves.

7. Maximize beneficial relationships and efficiency by “stacking functions.”
Get your water harvesting strategies to do more than hold water. Berms can double as high-and-dry raised paths. Plantings can be placed to cool buildings in summer. Vegetation can be selected to provide food.

8. Continually reassess your system: the “feedback loop.”
Observe how your work affects the site, beginning again with the first principle. Make any needed changes, using the principles to guide you.

Principles 2, 4, 5, and 6 are based on those developed and promoted by PELUM, the Participatory Ecological Land-Use Management association of east and southern Africa. Principles 1, 3, 7, and 8 are based on my own experiences and insights gained from other water harvesters.

These principles are the core of successful water harvesting. They apply equally to the conceptualization, design, and implementation of all water-harvesting landscapes. You must integrate all principles, not just your favorites, to realize a site’s full potential. Used together, these principles greatly enhance success, dramatically reduce mistakes, and enable you to adapt and integrate a range of strategies to meet site needs. While the principles remain constant, the strategies you use to achieve them will vary with each unique site.

For a thorough introductory description of water-harvesting principles and additional ethics see Rainwater Harvesting for Drylands and Beyond, Volume 1 (Rainsource Press, 2006).

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