Installation process of a 30,000 gallon modular, underground rainwater collection system. These modular units are constructed onsite, wrapped with layers of geotextile fabric and a impervious liner, and then covered. This system can be stacked up to 5 units tall which is 7.5'. We installed a submersible pump in the storage volume and connected it to a pump start relay controller so the pump will only turn on when the irrigation controller signals the pump start relay. This system is collecting from roughly 10,000 square feet of collection surface and has the capacity to collect about 200,000 gallons of rainwater per year.