Reservoir Size Calculator
Calculate hydroponic reservoir volume from plant count, system type, and refill interval. Size nutrient tanks for DWC, NFT, and drip systems.
Built for Hydroponics1 documented formula2 recommended next stepsPrivate in your browser
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Inputs that matter
Plant Count, Plant Size, System Type
Output to expect
Reservoir Size Calculator
How it works
1 documented formula across 1 calculation mode
- Keep 1 bounded input within the limits shown beside the fields.
- Confirm that every value uses the unit and time basis shown before comparing scenarios.
- Change one input at a time to see which assumption materially changes the result.
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Reference & details
How it works
Updated July 2026
How it works
Updated July 2026Per-Plant Volume
Deep water culture needs large per-plant volume. NFT and drip systems recirculate from a shared reservoir sized for total system demand.
DWC: 2–5 gal/plant | NFT: 0.1–0.3 gal/plant (flow) | Drip: 0.5–1 gal/plantDaily Consumption
Transpiration and evaporation deplete reservoirs daily. Size for 3–7 days between full changes or plan daily top-off volume.
Uptake ≈ 1–3% reservoir volume/day (mature plants)Minimum Volume
Add 20% safety margin for root zone expansion and evaporation. Larger reservoirs buffer pH/EC fluctuations.
Min volume = Plants × Per-plant volume × Safety factor (1.2)Updated: July 2026
Example Scenarios
4 large tomato plants at 5 gal each = 20 gal minimum. Use four 5-gallon buckets or single 25-gal tote with 20% margin.
200 lettuce heads on NFT channels with 50-gal reservoir — 0.25 gal/plant recirculated, changed weekly.
6 plants × 1 gal = 6 gal minimum reservoir. 10-gal tote provides buffer for 5-day change interval.
FAQ
Depends on system type. DWC: 2–5 gallons per plant. Recirculating NFT/drip: 0.5–2 gallons per plant minimum. Larger is more stable.
More volume buffers pH drift, EC changes, and temperature swings. Small reservoirs need daily monitoring; large systems tolerate minor imbalances.
Small systems: 1–2 weeks. Large commercial: 2–4 weeks. Change when EC drops significantly despite topping off, or pH becomes unstable.
Use food-grade plastic (HDPE, PP). Black or opaque blocks algae. Avoid metal containers — corrosion and ion leaching affect nutrients.
Commercial setups often maintain a separate top-off tank with pH-adjusted water auto-dosed to main reservoir. Size top-off for 1 week of evaporation/transpiration loss.
About Reservoir Size Calculator
Undersized reservoirs cause rapid pH and EC swings; oversized tanks waste space and nutrients. Enter number of plants, system type, and desired days between full changes to calculate minimum reservoir volume.