Cisterns & Large-Scale Rainwater Storage — FarmPal
Beyond rain barrels: cisterns store 500-10,000+ gallons for serious water independence. Sized correctly, a cistern can carry a household through dry months, supply a barn, or back up the garden through a drought.
Cost Range
$0.50-$2.00 per gallon installed (poly tanks); $3-6/gal (concrete)
Water Yield
Annual capture = roof area (sq ft) × annual rainfall (inches) × 0.62 × 0.9 efficiency
Key Points
- 💧Sizing rule: aim for 30-60 days of typical household use (50-100 gal/person/day)
- 💧Above-ground poly tanks are cheapest; below-ground concrete lasts 50+ years
- 💧Dark green or black tanks block sunlight and prevent algae
- 💧Code-compliant overflow is mandatory — route to swale, rain garden, or storm drain
- 💧In freeze zones: bury below frost line, insulate, or use a heated tank jacket
Installation Steps
- 1Size the tank: monthly water need × 2 = comfortable buffer in your driest stretch
- 2Pick location: gravity feed if possible, downhill of catchment, level pad required
- 3Pour or compact a level base — 6" of compacted gravel for poly, reinforced slab for concrete
- 4Install pre-tank screening + first-flush diverter (see related guide)
- 5Plumb inlet near top with calmed-inflow elbow (reduces sediment stir-up)
- 6Add an overflow at the same elevation, sized to handle peak storm flow
- 7Install draw-off pipe 6" above tank floor (above sediment layer)
- 8Add tank vent with insect screen, sight gauge, and lockable lid
Practical Checklist
Tap items as you go — progress is saved on this device.
0 of 17 complete0%
Supplies
Safety Steps
Testing & Verification
Tips
- 💡Two smaller tanks beats one big tank — redundancy + serviceability
- 💡A floating intake pulls the cleanest water from just below the surface
- 💡Annual maintenance: drain, scrub, and shock-chlorinate (then flush) every spring
- 💡Pair with a 12V on-demand pump for off-grid pressurized supply (~$150)
- 💡Many states offer rainwater rebates — check your state extension office