Natural Swimming Pools โ€” FarmPal

A natural swimming pool (NSP) uses a regeneration zone of aquatic plants and gravel biofilters instead of chlorine to keep water swim-clean. Pioneered in Austria in the 1980s, NSPs are now permitted in most US states and deliver crystal-clear water, wildlife habitat, and zero chemical exposure.

Cost Range
$15,000-80,000 pro install; $3,000-12,000 DIY pond-liner build
Water Yield
Stores 10,000-40,000+ gallons usable in drought emergencies (with appropriate treatment)

Key Points

  • ๐Ÿ’งTwo zones: swim zone (deep, clean) + regeneration zone (shallow, planted) โ€” regen zone is 30-50% of total area
  • ๐Ÿ’งNo chlorine, no salt, no UV needed โ€” plants and microbes do the filtration
  • ๐Ÿ’งWater tests cleaner than most public pools when properly designed and stocked
  • ๐Ÿ’งStays usable year-round; freezes solid in cold climates without harming the system
  • ๐Ÿ’งDoubles as a wildlife pond, fire-suppression reservoir, and emergency water store

Installation Steps

  1. 1Site selection: full sun on swim zone, shade tolerated on regen zone, away from leaf-drop trees
  2. 2Excavate two connected basins: swim zone 6-8 ft deep, regen zone 12-18 in deep with shelves
  3. 3Install EPDM pond liner (45 mil) over geotextile underlayment โ€” avoid PVC (leaches plasticizers)
  4. 4Build a hidden separator wall between zones โ€” water flows over the top, returns through gravel
  5. 5Fill regen zone with washed pea gravel (3-8 mm) โ€” this is the biofilter substrate
  6. 6Plant regen zone heavily: water iris, pickerelweed, watercress, hornwort, anacharis โ€” 4-6 plants/sq ft
  7. 7Install a low-watt circulation pump (40-100W) to move water swim โ†’ regen โ†’ swim continuously
  8. 8Cycle the system 4-8 weeks before swimming to let biofilm and plants establish

Practical Checklist

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Supplies

Safety Steps

Testing & Verification

Tips

  • ๐Ÿ’กSkimmer + bottom drain in swim zone removes leaves and settled debris with minimal energy
  • ๐Ÿ’กA small UV clarifier (off-label) can polish water in the first season while biology establishes
  • ๐Ÿ’กAdd a few minnows or shubunkins to control mosquito larvae โ€” they coexist fine with swimmers
  • ๐Ÿ’กCover regen zone with a low fence or use as a visual feature โ€” keeps dogs and kids out of plants
  • ๐Ÿ’กAnnual maintenance: trim plants in fall, vacuum swim zone bottom in spring, refill from rain
  • ๐Ÿ’กBooks: "Natural Swimming Pools" by Michael Littlewood; BioNova and Total Habitat are leading US designers