Short answerHold at least three days of peak demand for a direct-drive system, more for year-round livestock or cloudy climates. Each 2.31 ft of tank height above the outlet gives 1 psi of gravity pressure.
Key takeaways
- Store at least three days of peak demand for livestock.
- Every 2.31 ft of tank height gives 1 psi at the outlet.
- Lids, screened vents and an overflow led away from the pad prevent most tank trouble.
How many days
Store at least three days of peak demand for livestock, more where long cloudy spells are normal or the water is the animals' only source. For a garden under drip, one to two days is often enough because a missed day does less harm. The calculator assumes three days.
| Daily use | 3 days | 5 days |
|---|---|---|
| 100 gal | 300 gal | 500 gal |
| 400 gal (20 beef cows) | 1,200 gal | 2,000 gal |
| 1,000 gal (50 cows) | 3,000 gal | 5,000 gal |
Height is pressure
Each 2.31 ft of height above the outlet is 1 psi. A tank on a 10 ft stand gives about 4.3 psi at ground level; one 50 ft up a hill gives about 21.6 psi, enough for a house with patience and for most drip systems. The pump has to lift the water that extra height, which adds to its head, but it does that once and slowly; you then draw the pressure for free.
Tank details that cause trouble
- Put the inlet at the top and a float switch where it stops the pump before the overflow runs.
- Run the overflow well away from the tank base so it does not undermine the pad.
- Fit a lid and screened vents: open tanks breed mosquitoes and algae and collect drowned wildlife.
- Dark or opaque tanks limit algae. Bury or insulate in cold climates.
- For stock, a float valve in the trough fed from the tank keeps the trough small and fresh.
Put your own gallons, lift and pipe in and see every step of the working.