Math first: at 2 GPA, a 300-acre day needs 600 gallons of finished mix. That's two 300-gallon nurse tanks — or one tank plus a confirmed refill source within a short drive.
Sourcing options, ranked by hassle
- Farm well/hydrant on site — fastest, but respect the air gap (see below) and ask permission explicitly.
- Rural water/bulk station — reliable, metered, may charge; know the hours before you plan around it.
- Co-op fill — convenient when buying chemical there anyway.
- Pond/stream — last resort: sediment clogs screens, and drawing from surface water raises legal and contamination questions. Filter aggressively if you must.
Never contaminate the source
Maintain an air gap — the fill hose stays above the tank's water line — or use a check valve. A submerged hose plus a pressure drop siphons pesticide back into a well, which is a catastrophic, expensive, and entirely preventable event. Mix well away from the wellhead (see mix/load safety).
Water quality quietly ruins applications
- Hardness: calcium/magnesium tie up glyphosate and some other herbicides — AMS or a water conditioner fixes it. Hard water without conditioner = weak weed control blamed on the wrong thing.
- pH: some products hydrolyze fast in alkaline water; check the label for pH guidance and buffer if needed.
- Sediment/algae: plugs screens and atomizers — filter at fill, not at the aircraft.
- Temperature: very cold water can affect mixing of some formulations; mix a little longer.
Test your regular source once. It's a cheap water test that explains a season of "why didn't that work?"
Nurse tank setup
- 300–500 gal poly tank, secured and baffled if possible
- 2" gas transfer pump + camlock fittings (speed = acres)
- Inline filter/screen before the drone tank
- Separate clean-water tank for rinsing and hand washing
- Air gap or anti-backflow device at every fill point
General practice; follow state rules on water withdrawal and backflow prevention. Setup context: field station.
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