Field Guide · Water
One foot of height buys 0.433 PSI. Here is what that means for drip.
Every foot of height above the outlet gives you 0.433 PSI. A barrel sitting three feet off the ground produces about 1.3 PSI. Standard drip emitters want 10 to 25 PSI, so gravity alone will not run them.
This is the number that decides whether your barrel can feed drip line, and it is almost always left out of the guides.
| Height of water surface above the outlet | Pressure |
|---|---|
| 2 feet | 0.87 PSI |
| 3 feet | 1.30 PSI |
| 4 feet | 1.73 PSI |
| 6 feet | 2.60 PSI |
| 8 feet | 3.46 PSI |
| 10 feet | 4.33 PSI |
To reach 10 PSI you would need the water surface 23 feet above the outlet. That is a roof tank, not a barrel.
| Method | Needs | Works on gravity? |
|---|---|---|
| Soaker hose | 1 to 5 PSI | Yes, on a short run |
| Micro tubing with 0.5 to 2 GPH emitters | 2 to 5 PSI | Yes |
| Pressure compensating drip emitters | 10 to 25 PSI | No |
| Olla irrigation | None | Yes, it does not use pressure at all |
| Flooding a furrow | None | Yes |
A full 55 gallon barrel weighs around 460 pounds. Raising it high enough to matter means a structure that can carry that load, and you still only reach single digit PSI.
The practical answer is to match the delivery method to the pressure you have. Micro tubing and soaker hose work. Pressure compensating emitters need a pump or mains water.
Keep the run short and level, and run it downhill if the ground allows. Slope adds effective head. Keep the outlet clean and use a filter, because a partly blocked emitter drops flow fastest when pressure is low.
Rain Catchment Blueprint
Pressure is one number. The blueprint covers barrel sizing, siting, first flush, and the plumbing that gets water where you want it, all on gravity.
Read the rain catchment blueprint →Not for soaker hose, micro tubing or ollas. You do need one for pressure compensating drip emitters, which want 10 to 25 PSI and will only get about 1 to 3 PSI from gravity.
It depends on height, not volume. A barrel with three feet of water above the outlet gives about 1.3 PSI, whatever its size.
Yes, on a short run. Soaker hose needs 1 to 5 PSI, so keep the length modest and the barrel raised two to three feet.
As high as your structure safely allows, but do not expect much. Going from 3 to 6 feet takes you from 1.3 to 2.6 PSI. A full barrel weighs about 460 pounds, so the stand matters more than the extra foot.
Rain Catchment Blueprint
Pressure is one number. The blueprint covers barrel sizing, siting, first flush, and the plumbing that gets water where you want it, all on gravity.
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