A pool was always part of the homestead vision — not a chlorinated rectangle, but a swimming hole that looked like it had always been there. We excavated it over three weekends with a rented mini excavator and built the biological filtration system from scratch. Total cost: $8,412. No pool company, no chemicals, no fiberglass shell.
The Concept: Biological Filtration
A natural pool is two connected bodies of water: a swimming zone and a regeneration zone. The swimming zone is where you swim — clear water with no vegetation. The regeneration zone is a planted gravel bed where water circulates through aquatic plants that absorb nutrients and outcompete algae. The plants do the filtering work that chlorine does in a conventional pool.
You're not fighting nature — you're using it. A balanced planted aquatic ecosystem is self-maintaining. It doesn't need chemicals, shocking, or service visits.
Swim Zone: ~20'×30', 5' deep center
Regen Zone: ~8'×20', 24" planted gravel bed
Entry: Gradual sand beach, 0" to 4' depth
Chemicals used: Zero. Ever.
Excavation
We rented a 1.7-ton mini excavator for three weekends at $380/weekend. The sand beach entry required the most careful work — a gradual 10-degree slope from dry land down to swimming depth. We formed the beach transition with compacted sand over the clay base.
Liner and Waterproofing
45-mil EPDM pond liner — UV-stable, fish-safe, flexible enough to conform to the excavated shape. Before placing it, we laid 4 inches of sand over all surfaces to protect against sharp rocks. The liner transitions naturally into the sand beach at the entry end.
The Filtration System
The regeneration zone is 18 inches of washed pea gravel over a perforated drainage layer, planted with pickerelweed, blue flag iris, water horsetail, arrowhead, rushes, and sedges. A 2,000 GPH submersible pump circulates pool water up through the planted gravel bed and back over a stone weir into the swim zone. The entire volume turns over every 4–6 hours.
The Sand Beach
Four tons of fine masonry sand over the liner creates the beach zone. You walk in gradually, naturally — like a lake. No cold metal ladder, no sudden drop-off. It's been extremely stable and requires minimal topping up.
Full Cost Breakdown
| Item | Cost |
|---|---|
| Mini excavator rental (3 weekends) | $1,140 |
| 45-mil EPDM liner (40'×60') | $1,850 |
| Underlayment sand + beach sand | $600 |
| Pea gravel regen zone (8 tons) | $640 |
| PVC pipe, fittings, pump | $405 |
| Aquatic plants (initial stocking) | $380 |
| Natural stone edging and weir | $840 |
| Electrical (outdoor outlet + wiring) | $560 |
| Miscellaneous | $197 |
| Total | $8,412 |
Ongoing Maintenance
First season: 6-week plant establishment period with a brief algae bloom. We skimmed the surface and waited. Once plants established, algae cleared on its own and hasn't returned. Second year onward: pump runs 24/7 (~$15/month electricity), we trim aquatic plants in fall, and occasionally vacuum bottom debris. About 6 hours of total maintenance in year two.
The water is genuinely clear. You can see the bottom in the deep section. And it cost $0 in chemicals and $0 in pool service — ever.