While most of our residential rainwater harvesting systems installation involve a simple procedure for getting the rainwater harvesting cistern into place, we have had a few projects over the years that have definitely presented a challenge for us. While we have never come across a challenge that we couldn’t meet, it has made for some very interesting installations. This project was definitely one of them.
The homeowner was building a new house on a lot that had a high degree of slope from the street to the back property line. The multi-story house design will allow for a wonderful view of Lake Austin but in order to achieve the view, the floor elevation of the house produced a basement area underneath the backside of the house. This provided us the perfect opportunity to design a rainwater harvesting system that used the property’s slope to our advantage.
An exterior wall was built that created the basement area. A compacted base of granite gravel was installed in the basement area which would be the foundation for the cisterns. While a concrete foundation for a rainwater cistern is feasible, in most cases, it is not necessary to go to the expense of a concrete foundation. Rainwater cisterns have an even distribution of weight so they don’t need a concrete foundation to help distribute points loads as you would have in a building structure.
The video below shows the journey of the rainwater cisterns from the closest highway, through a residential neighborhood, to the project site. We carefully surveyed the path to get the cistern delivery truck to the site so that we would not have any issues with overhead power lines, etc. Once at the property, the cisterns had to be turned right side up since they were shipped to site on their sides. Then, a crane was used to lift the approximately 2,500 lbs cisterns from the street cul-de-sac to the tank location which was approximately 150 feet.
Do you want to consider a rainwater harvesting system for your new home project but you think you may have a difficult site? No problem! With our experience and expertise, we can design the most optimal and cost-efficient system for you. Give us a call at 512-490-0932 or request a consultation here.
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Chris,
I want to install a 5,000 gallon tank in the back yard in Dallas. Can that size of tank be set on a compact granite gravel base? If so, what depth do you recommend? Do you hire out to engineer proper bases?
Jesse, thanks for the question. For the most part, a compacted granite gravel base is sufficient for most residential tanks. While you might have some compaction and settling of the soils below the granite gravel base over time, the only thing it will affect are the piping connections to the tank. So if the settling is too much for the piping connections to hold, then they can be replumb fairly easily.
For the depth, I would recommend at least a 6″ depth to the granite gravel, compacted in lifts.
For tanks that are taller than they are wide, some cities may require an engineered concrete foundation due to the overturning potential of the tank.
As a disclaimer, I should say that you should consult a local engineer if you feel like the tank foundation could be an issue in your location.