Tank Size by Application
Not sure where to start? Here's a quick overview of recommended tank sizes for the most common applications. Use the calculator above for a more precise recommendation based on your specific numbers.
Emergency / Backup Water Supply
FEMA recommends 1 gallon per person per day for drinking and sanitation. For a 30-day supply for a family of 4, that's 120 gallons minimum — making a 150- or 200-gallon tank a practical choice. For 90 days of supply, a 500-gallon tank covers a family of 4 comfortably. Add 20% buffer for cooking and hygiene needs beyond drinking.
Livestock Watering
Daily water consumption estimates by animal type:
| Animal | Gallons / Day | 10-Animal / Day | 7-Day Supply (10 animals) |
|---|---|---|---|
| Chickens (laying hens) | 0.07 gal (9 oz) | 0.7 gal | 5 gal |
| Goats / sheep | 1–3 gal | 10–30 gal | 70–210 gal |
| Pigs | 3–5 gal | 30–50 gal | 210–350 gal |
| Cattle (beef) | 30–50 gal | 300–500 gal | 2,100–3,500 gal |
| Horses | 10–12 gal | 100–120 gal | 700–840 gal |
Pressure Washing Buffer Tank
For a 4 GPM pressure washer connected to a hose bib (3 GPM): you're short 1 GPM. An 8-hour day at 50% trigger time means ~240 gallons consumed. A hose bib supplying 3 GPM × 8 hours = 1,440 gallons in — you have plenty. The buffer tank (50–100 gallons) just smooths out pressure drops and spikes. For fully independent operation (no hose bib), a 500-gallon tank is the standard for a full-day commercial rig.
Off-Grid Household Supply
Average US household uses 80–100 gallons per person per day (including laundry, showers, toilet, cooking). A family of 4 at 80 gallons/day needs 320 gallons/day. A 2,500-gallon tank provides about 8 days of full-household supply; a 5,000-gallon tank gives approximately 16 days. For true off-grid living with a well or rainwater collection, the tank buffers between collection events and daily use.