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Our Mission

To help you understand the specifics involved in designing and installing a rainwater harvesting system that meets your needs -- anything from potable water systems for your home, to satisfying the thirst of animals, to emergency stores, to water for gardens and landscaping.  

Our Story

Grainger & Sunn Rainwater Harvesting Consultants sprang out of a perceived need to unite business, banking, and builders, while helping beneficiaries--hill country homeowners better understand the benefits and need to harvest nature's free water. 


When you decide to install a rainwater harvesting system, several questions require answers. Though rainwater harvesting systems are not complex and are easy to install, there are some perplexing pre-installation factors that need to be clarified. Comal County's Grainger & Sunn Rainwater Harvesting Consultants can help you understand the specifics involved in designing and installing your rainwater harvesting system.  Our services are offered to Comal and surrounding county residents without charge--courtesy of the Comal Trinity Groundwater Conservation District.


Steven Grainger, PhD

Doctorate from Texas A & M

Hydrologist and Good Guy

Master Gardener;

Dr. Steven Grainger is a retired Aggie Texas Professional Engineer who turned to Master Gardening yet still practices his analytical skills.  He specializes in Irrigation Efficiency and Rainwater Harvesting, but is currently also working to specialize in Trees and Tree Care.  He has been a Master Gardener in Comal County for 10 years having served once as President, and now serves as Water Conservation Chair and Vice Chair of the AgriLife Extension Facilities Steering Committee. He also has served as  Outreach Co-chair on the Comal County Conservation Alliance Board of Directors. As a person deeply committed to preserving our natural land and water resources, he and his wife of 52 years actively encourage others to do so, too.  He can also advise on landscaping for water efficiency and retention or storm water management.  Our services are always free and we welcome questions anytime.

"Our services are always free and we welcome questions anytime."


Larry Sunn, EdD

Supreme Commander

Doctorate from BYU in Statistics & Research

2015-2023, Director, Comal Trinity Groundwater Conservation District

Director, Healthcare Innovation Sciences

A retired career Marine Captain, and a retired 25-year university professor of statistics and research from the University of Redlands, Dr. Larry Sunn consults free of charge, with area residents interested in rain harvesting systems.  Dr. Sunn served his community as a member of Comal Trinity Groundwater Conservation District’s Board of Directors from 2015 to 2023; he is currently a Director on the Board of the HISCentre, and at this time he is President of the Bulverde Community Park Association.  He and his wife of 60 years have lived on the west side of Bulverde for past 23 years.  Informed early in his life that he could become whatever he wanted to become, Dr. Sunn chooses to be a Supreme Commander.

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Dr. Sunn's Rain Harvesting Systems

I have rain catchment systems on four structures; I harvest up to 186,000 gallons of water per year--we get an average of 30 inches of rain here in Comal County.  My system was developed and installed with the consulting help of Dr. Steven Grainger.  Here are some quick guidelines he had me think through when designing my two rainwater harvesting systems:

  1. Direct:  Establish gutters, tank elevation for gravity feeds, and consider both wet or dry conveyance piping captures for my rooftop water.  I have both wet and dry conveyance.

  2. Capture: Install metal roofs on structures; I have a series of sealed downspouts with three levels of filtering, along with an overflow system, that are installed at each catchment base.

  3. Collection: Storage tanks can be as simple as a 50-gallon rain barrel, large plastic or metal tanks, or a complex array of linked tanks.  I have one 6,000-gallon and one 5,000 gallon poly tank for capturing water for my garden, and one main, potable water, metal, 50,000 gallon catchment tank.  My garden tanks are not linked and provide water just to my garden.

  4. Storage: The tanks need to be able to capture and move the water where desired.  I capture rain water via a "dry piping" conveyance off of two out buildings for the garden, and I catch water for the potable, main tank, via a "wet pipe" conveyance, and then pump the water from the respective storage tanks to the points of use in the garden, guest house, and main house.

  5. Use:  The garden water is pre-storage tank filtered via leaf guards on my rain gutters, I have "Leaf Eater" screens on my downspouts (mosquito prevention), and I installed "Maelstrom Filters" on my two garden tanks.  No other filtration is needed for garden use--plants love rain.  The potable system has the same three pre-storage tank filters as the garden tanks and then a post-storage tank filtration system that includes a "spin down" filter, 20-micron and 5-micron particulate filters, followed by water passage through a UV light filter that neutralizes any pathogens. 

  6. Pumping:  Last, having post-storage tank "Walrus" pumps allows me to move water to different locations under high pressure if needed.  I can even wash my cars via captured rain!

Once you move toward capturing rain, like me, you become more "water aware" and look for new ways to use and more ways to store nature’s bounty.   My garden tanks--11,000 gallons--overflowed this year (2021) by June!   


Dr. Grainger and I watch and monitor Trinity aquifer water tables in the Comal Trinity GCD's 10 monitoring wells; we see them steadily declining, and we know that “water is the new gold.”

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50,000 tank


5,000 tank (2)

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6,000 tank

Make a difference . . . together

Rain harvesting materials and equipment are sales tax free--complete this form

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