Rainwater Cleaning & Filtration Stack — FarmPal

Make stored rainwater safe for laundry, dishes, showers, and (with the final stages) drinking. A proper filtration stack works in layers — each stage removes a specific class of contaminant, and skipping stages is the most common reason home systems fail water testing.

Cost Range
$200 (non-potable) to $1,200+ (full potable stack)
Water Yield
No yield change — improves quality of harvested water

Key Points

  • 💧Five-stage potable stack: sediment → carbon → 1-micron → UV → optional RO
  • 💧Non-potable (irrigation, toilets, laundry): sediment + carbon is enough
  • 💧UV sterilizes living organisms but does NOT remove chemicals or sediment
  • 💧Test annually: total coliform, E. coli, pH, turbidity, lead (if old roof flashing)
  • 💧Storage tanks need to be opaque and food-grade — sunlight breeds algae fast

Installation Steps

  1. 1Stage 1 Sediment: 20-micron pleated cartridge catches grit, leaves, insect parts
  2. 2Stage 2 Carbon block: 5-micron activated carbon removes chlorine, taste, VOCs, some pesticides
  3. 3Stage 3 Fine filter: 1-micron absolute removes cysts (cryptosporidium, giardia)
  4. 4Stage 4 UV sterilizer: 30+ mJ/cm² dose kills bacteria, viruses, protozoa
  5. 5Stage 5 (optional) RO membrane: removes heavy metals, nitrates, dissolved solids
  6. 6Install in this order — UV last so it treats already-clear water (UV needs <5 NTU turbidity)
  7. 7Add pressure gauges before and after sediment stage; replace cartridge when ΔP > 10 PSI
  8. 8Get a baseline lab water test before drinking; retest every 12 months

Practical Checklist

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Supplies

Safety Steps

Testing & Verification

Tips

  • 💡For drinking only: a Berkey-style gravity filter ($300) replaces stages 1-4 with no electricity
  • 💡UV bulbs lose 30% output annually — replace every 12 months even if still glowing
  • 💡Boiling is a free emergency backup for biological contamination (rolling boil 1+ minute)
  • 💡Slow sand filters ($150 DIY) are off-grid friendly and remove >99% of pathogens
  • 💡Never trust a single stage for potable water — defense in depth is the rule
  • 💡Chlorine bleach shock (1 tsp unscented bleach per 10 gal, 30 min) sanitizes a tank annually