# Sovereignty Module: Cast the Cistern

## Complete Ferrocement Water Tank Construction: From Wire to Water Storage

Ferrocement tanks provide affordable, durable water storage that can be built with basic materials. This campaign covers design, armature construction, plastering, curing, and waterproofing.

### Chapter 1: Design Principles

| Tank Shape | Capacity | Structural Efficiency | Difficulty | Best For |
|---|---|---|---|---|
| Cylindrical | 500-10,000+ gallons | Excellent (hoop stress) | Moderate | Most applications |
| Rectangular | 200-2,000 gallons | Moderate (needs reinforcement) | Moderate | Tight spaces |
| Dome/spherical | 500-5,000 gallons | Excellent | High | Underground |
| Jar (olla) shape | 100-1,000 gallons | Very good | Moderate | Above ground, traditional |

Sizing: 1) 1 cubic foot = 7.48 gallons. 2) Cylindrical tank: Volume = pi x radius squared x height. 3) Example: 4-foot radius x 4-foot height = 201 cubic feet = 1,503 gallons. 4) Wall thickness: 1-2 inches (ferrocement is thin-shell construction). 5) Foundation: flat, level, compacted surface or concrete pad. 6) Overflow: pipe at maximum water level. 7) Outlet: pipe near bottom (with valve). 8) Access: manhole or removable lid for cleaning. 9) Vent: screened opening prevents vacuum during draining.

### Chapter 2: Armature Construction

| Component | Material | Function | Specification |
|---|---|---|---|
| Skeleton | Rebar (3/8 inch) or welded wire mesh | Primary structure | Vertical and horizontal rings |
| Mesh layer 1 | Chicken wire (1 inch hex) | Mortar support | Wrapped around skeleton |
| Mesh layer 2 | Hardware cloth (1/2 inch) | Fine mortar support | Over chicken wire |
| Tie wire | Galvanized wire (18-20 gauge) | Connect all layers | Every 6-8 inches |

Cylindrical tank armature: 1) Set vertical rebar rods in foundation (every 8-12 inches around circumference). 2) Bend horizontal rebar rings to match tank diameter. 3) Tie horizontal rings to verticals at every intersection. 4) Wrap chicken wire around entire frame (inside and outside). 5) Overlap chicken wire by 2 inches at all seams. 6) Tie chicken wire to rebar at every 6 inches. 7) Optional: add hardware cloth layer for smoother finish. 8) Armature should be rigid (no flexing when pushed). 9) All wire ends must be tucked in (no protrusions). 10) Leave openings for inlet, outlet, overflow, and access.

### Chapter 3: Plastering

| Mortar Mix | Cement | Sand | Water | Strength | Use |
|---|---|---|---|---|---|
| Standard | 1 part | 2-3 parts | As needed | Good | General walls |
| Rich mix | 1 part | 1.5-2 parts | As needed | Very good | First coat, waterproofing |
| Waterproof mix | 1 part + waterproofer | 2 parts | As needed | Very good | Final interior coat |

Plastering process: 1) Mix mortar to thick, workable consistency (not runny). 2) Wet armature thoroughly before plastering. 3) Apply first coat from inside (push mortar through mesh). 4) Work from bottom up. 5) First coat: fill mesh completely (1/2 inch thick). 6) Let first coat set but not dry completely (24 hours). 7) Apply second coat from outside (covers all mesh). 8) Total wall thickness: 1-1.5 inches. 9) Smooth interior surface (water contact side). 10) Apply waterproof coat to interior (cement + waterproofing additive). 11) Keep moist during curing (cover with wet cloth or plastic). 12) Cure for minimum 7 days (28 days for full strength).

### Chapter 4: Waterproofing

| Method | Cost | Effectiveness | Durability | Food Safe |
|---|---|---|---|---|
| Cement + waterproofing additive | Low | Very good | Very good | Yes (most brands) |
| Bituminous coating | Low | Excellent | Good | No (exterior only) |
| Epoxy coating | Moderate | Excellent | Excellent | Yes (food-grade) |
| Lime plaster (interior) | Very low | Good | Good | Yes |
| Silicone sealer | Low | Good | Moderate | Varies |

### Chapter 5: Testing and Commissioning

| Test | Method | Pass Criteria | Action if Fail |
|---|---|---|---|
| Visual inspection | Examine all surfaces | No cracks, holes, or exposed wire | Patch with mortar |
| Fill test | Fill with water, mark level | No drop in 48 hours | Find and seal leak |
| Tap test | Tap walls with hammer | Solid sound (no hollow spots) | Replaster hollow areas |
| Pressure test | Fill to overflow | No bulging or cracking | Reinforce weak areas |

### Reference Card

1. Cylindrical is strongest (the cylinder distributes water pressure evenly as hoop stress; it is the most efficient shape for water tanks). 2. Multiple mesh layers are key (ferrocement strength comes from multiple thin layers of mesh embedded in mortar; more layers equals more strength). 3. Tie everything together (every intersection of rebar and mesh must be tied with wire; loose connections create weak points). 4. Plaster from inside first (pushing mortar through the mesh from inside ensures complete penetration and eliminates voids). 5. Cure for 28 days (cement reaches full strength at 28 days; keep the tank moist during curing by covering with wet cloth). 6. Waterproof the inside (the interior surface must be sealed to prevent water from seeping through; use cement with waterproofing additive). 7. Ferrocement is cheaper than any alternative (a DIY ferrocement tank costs a fraction of a commercial plastic or concrete tank of the same size). 8. One tank changes everything (reliable water storage transforms a homestead; build the largest tank you can afford and maintain).