Sizing and Designing Concrete Underground Water Tanks
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Concrete subterranean water tanks are a safe and efficient solution for long-term water storage. However, they require careful considerations such as location, design, capacity, and connection to the water supply. This guide aims to provide best practices for homeowners and contractors in sizing and building functional installations. By following these guidelines, you can ensure your concrete underground water tanks structural integrity is preserved for years of use and that it meets your long-term water storage needs.
Calculate Water Demand
Calculate gallons needed daily for drinking, irrigation, livestock, or fire suppression based on property uses and size. Include expansion room for future needs. Determine daily gallons needed for at least 1-2 weeks based on property/building uses, number of occupants, irrigation needs, livestock, fire suppression requirements, etc. Include extra capacity for future expansion.
Consider Tank Placement
Plan for easy access in case repairs are needed. Tanks require setbacks from retaining walls and power lines during excavation for installation. Locate for easy access in case repairs are needed via a maintenance hole. Consider setbacks needed during excavation and ensure not under retaining walls or power lines.
Design for Weight Support
Compact soils fully before pouring concrete to prevent settling. Reinforcement adds strength to the weight of the full tank, soil, and traffic load above.
Decide on Tank Shape and Dimensions
Circle, rectangle, or custom shapes work depending on space. Standard sizes offer installation efficiency for contractors with precast components. Have soils fully compacted before pouring to prevent settling under the weight of full concrete/soil/traffic above. Reinforcing like rebar adds strength.
Select Wall Thickness
Newer ASTM standards dictate minimums based on depth to prevent issues like bowing or collapsing. Experts help choose adequate reinforced thickness. Circular, rectangular, or custom shape based on space. Standard sizes make precast components available.
Design Tank Features
Vents and access ports at the top allow entry. Inlet/outlet pipes position for gravity-fed flow. The drain allows emptying for maintenance. Baffles reduce water movement inside. Thicker walls (6-12 inches) prevent issues for deep tanks per ASTM. However, concrete contractors can help choose adequate reinforced thickness.
Add Water Protection
Interior sealers and exterior tank coatings combined with drainage gravel surrounding the tank keep water out and contained properly. Add venting, access ports/lids, inlet/outlet pipes positioned for gravity flow, drain valve, and interior baffles to reduce water movement.
Consider Partitioning
Multiple compartments provide a backup supply or separate uses like rainwater harvesting. Contamination prevention separators isolate sections. Interior sealers and exterior tank coatings, along with surrounding drainage gravel/filter fabric, prevent water intrusion and containment issues.
Determine Water Connection
Pipes of proper diameter efficiently fill and release tank capacity whether connecting to a well system, public supply, or other sources. Backflow preventers are installed where required. Multiple sections can provide standby supply or separate uses like rainwater. Contamination prevention barriers isolate portions.
Create Site Plan
Indicate tank, dimensions, setbacks, and driveways in engineering drawing for contractor installation approval by local authorities. Installation complies with regulations. In/out pipes of correct diameter efficiently fill/empty tank capacity from well, public supply, or another source. Backflow devices as required.
Conclusion
Thorough planning results in durable, compliant underground tanks meeting all water needs now and in later years according to standards with safety as a priority. Experts address concerns for optimized service life.
