1,000-Gallon Underground Tank
The 1,000-Gallon Underground Tank provides 1,000 gallons of rainwater storage in a underground polyethylene container measuring 72" x 56" x 48" (buried). Priced between $800 and $1,500 ($0.80-$1.50 per gallon of capacity), this tank is a practical mid-range option for homeowners with dedicated irrigation or non-potable indoor needs.
About the 1,000-Gallon Underground Tank
Underground tanks keep your rainwater storage completely out of sight, preserving yard aesthetics and complying with HOA requirements that may restrict above-ground tanks. A buried 1,000-gallon tank connects to your gutter downspouts through underground PVC piping. The soil surrounding the tank provides natural insulation, keeping water cooler in summer and preventing freezing in moderate climates. Installation requires excavation, a gravel bedding layer, and backfilling with clean sand or pea gravel. The tank must be rated for underground burial — standard above-ground tanks will collapse under soil pressure. Access is through a ground-level lid for inspection and cleaning. A submersible pump is required to deliver water from the tank to your irrigation system. While installation costs are higher than above-ground options, underground tanks offer a clean, unobtrusive solution that adds no visual clutter to your property.
Installation Guide
A 1,000-gallon tank requires more preparation than a simple rain barrel but is still within reach of experienced DIY homeowners. The most critical step is preparing a proper foundation. When full, this tank weighs approximately 8,340 pounds — that weight must be distributed evenly on a surface that will not shift or settle.
Pour a 4-inch concrete pad extending 6 inches beyond the tank footprint on all sides, or prepare a compacted gravel bed at least 6 inches deep. Ensure the pad is perfectly level using a builder's level. Connect downspouts to the tank inlet using schedule 40 PVC pipe, with a leaf screen or gutter guard at each collection point. Install a first-flush diverter to improve water quality by discarding the first gallon per 100 square feet of roof after each dry period.
Recommended Accessories
- First-flush diverter (1 gallon per 100 sq ft of roof)
- Calmed inlet to reduce sediment disturbance
- Tank-level gauge (float type or electronic)
- Submersible or external pump for pressurized delivery
- Overflow pipe routed to rain garden or storm drain
- Bottom drain valve for annual cleaning
Best Uses for the 1,000-Gallon Underground Tank
The 1,000-Gallon Underground Tank serves homeowners with dedicated vegetable gardens (500-2,000 sq ft), drip irrigation systems, lawn watering needs, and indoor non-potable applications like toilet flushing. At 1,000 gallons, it stores enough water to bridge typical dry periods of 1-3 weeks in most climates. This size is also popular for small livestock operations, greenhouse irrigation, and properties seeking to reduce their municipal water consumption by 30-50%.
States Where the 1,000-Gallon Underground Tank Is Recommended
Based on our calculations for a 1,500-square-foot asphalt shingle roof used for garden irrigation, the 1,000-Gallon Underground Tank is the recommended storage size in the following states:
- Arizona — 13.6" annual rainfall
- Colorado — 15.9" annual rainfall
- Montana — 15.3" annual rainfall
- Nevada — 9.5" annual rainfall
- New Mexico — 14.6" annual rainfall
- North Dakota — 17.8" annual rainfall
- Wyoming — 12.9" annual rainfall
Your actual recommended tank size depends on your specific roof area, material, intended uses, and household size. Use our calculator for a personalized recommendation.