BlueBarrel's founder demos her gravity-fed DIY drip irrigation system. Four rain barrels supply the water, and gravity does the work to hydrate her garden beds.
Can you Irrigate from Rain Barrels with Just Gravity?
Yes! A properly designed rain barrel system can water gardens, raised beds, and landscaping using gravity alone, without electricity or pumps.
The key is sufficient elevation, proper plumbing, and irrigation components designed for no-to-low pressure.
In this guide, we explain:
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How gravity irrigation works
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How much height you need
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What types of irrigation systems are compatible
- What parts you don't need
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When a pump is necessary
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Components for success with gravity-fed irrigation
If you're starting from scratch, consider a BlueBarrel Rainwater Catchment System®. This specialty rain barrel system is plumbed for optimal gravity-fed performance, including a fully bottom-draining design, high-flow valves and more.
That said, any rain barrel, cistern, or tank can be paired with our gravity-fed drip irrigation kits as long as you follow the basic principles covered in this article. Read on for a complete primer!
Your rain barrels are full. Now what?
Rainwater harvesters know how fast and easy it is to fill a rain barrel—or a series of them—from the roof. But once those barrels are full, how do you distribute this precious stored water through the garden? When you let gravity do the work, that part can be easy, too.
Drip irrigation is the most water-efficient way to irrigate. When you rely on gravity for distribution, it is also the most energy-efficient.
Even BlueBarrel's standard cinderblock foundation provides enough lift to distribute water over a flat site. The bottom-draining design allows all barrels to feed a single irrigation outlet. Additional irrigation valves can be added to extend the irrigation area in both directions.
How Gravity Irrigation From Rain Barrels Works
Gravity irrigation relies on one simple principle: water flows downward and outward until something stops it.
When rain barrels are positioned higher than the irrigation area, even by a millimeter, gravity creates enough force to move water through properly-sized tubing and into your garden. No electricity or pump required.
Unlike pressurized household systems, gravity-fed systems operate at very low pressure. The goal is not to spray water—it is simply to deliver a steady flow that can fill the mainline and supply emitters or soaker tubing.
This approach works best when:
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The irrigation area is at or below the water level in the barrels
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Distances are reasonable
- Tubing is sized appropriately
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Components are designed for no-to-low pressure
When designed correctly, gravity systems can provide reliable, automated watering for gardens, raised beds, and landscaping.
This graphic illustrates the principles of gravity-fed irrigation. The system on the left will work no matter how full the barrels are. The system on the right will work when the barrels are full, but as the water level drops toward the high-point in the line, flow will stop.
Do you need a slope like this to create gravity pressure? No! Water always seeks its level, so even on a flat site, water will distribute through a gravity-fed mainline as long as the line doesn't rise above the water level in the barrels.
Elevation: The Key to Performance
Drip irrigation doesn't actually require any pressure, it just requires water in the line.
Water will keep flowing downward and outward until it has nowhere else to go. As long as your drip line stays below the water level in your barrels, you can irrigate with gravity.
Height is the single most important factor in a gravity-fed system.
Every 1 foot of elevation produces 0.43 PSI of water pressure.
Systems elevated several feet above the garden perform best, but even minimal elevation can work for a smaller landscape area right near the rain barrel(s).
Some sloped sites provide a natural setup for this, with gardens situated downhill from the buildings collecting rain. On flat sites, barrels can be elevated on raised foundations.
A simple wooden foundation adds height for this painted BlueBarrel System on an otherwise flat site.
A metal frame elevates this wood-clad BlueBarrel System for additional gravity advantage.
Most setups fall into one of these categories:
0–1 ft elevation (flat sites, ground-level)
Can work for small, nearby irrigation zones.
2–5 ft elevation (moderately sloped sites, or elevated barrels)
Suitable for many typical home gardens and raised beds.
6–10+ ft elevation (hilly sites)
Provide the strongest flow and greatest flexibility in layout.
Remember: You do not need high pressure. Drip irrigation technically doesn’t require any pressure, it just requires water in the line. You only need enough force for water to flood the mainline and move through the system.
As long as gravity can get water into your irrigation line, you do not need pressurized water. Just make sure you:
- Use non-restrictive supply lines
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Use timers, filters, and emitters that are designed for gravity-feed (examples below)
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Follow max line length guidelines (also below)
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Don't ask water to flow uphill
This 6-barrel System irrigates a water-wise garden with gravity-fed drip irrigation. The gentle slope towards the sidewalk allows for great distribution through the drip line, and adjustable bubbler emitters allow the user to control how much water each plant gets. A native plant palette and mulch cover maximize the water-efficiency of this setup.
With a BlueBarrel System, you can run more than one drip line to reach more of your garden. In the photo above, for example, there is a drip irrigation connection on Barrel 1 and another on Barrel 6 to reach plants in opposite directions. Tee off the main lines to service the entire area in between using a grid or "fork" pattern. The gravity-fed irrigation kits available in our Online Store include fittings to create these basic layouts.
If you follow the principles of gravity, rain barrel irrigation systems are completely customizable to your garden.
Distance and Layout Considerations
Water can travel long distances through a properly sized mainline, as long as the line stays flat or downtrending.
Key design principles:
- Keep irrigation zones close to the barrels when possible, especially on flat sites
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Avoid unnecessary bends and restrictions
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Use larger-diameter mainline tubing to reduce friction
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Lay your line for level or downhill flow
Ground-level barrels on flat sites often perform best within about 20–50 feet, though longer runs are possible when tubing is sized appropriately, and when micro-topography doesn’t create too much “up and down.”
EXPERT TIP: We used to advise that gravity-fed irrigation systems on flat sites perform best within 25’ of the water source in all directions. But after years of observation, we learned that a 1/2" mainline is broad enough to carry the water much farther. Raised beds can be irrigated by gravity if the water level in your barrels remains above the entire feeder line. Ups and downs will begin to limit the distance you can distribute water. This is because you need extra head-pressure (water level) in your barrels to push the water over any rise.
Why Mainline Design Matters
The mainline is the backbone of the irrigation system. It distributes water from the barrels to the rest of the network.
A properly sized mainline (provided with our gravity-fed irrigation kits) can carry water across large areas because it offers minimal resistance. Problems usually arise not from distance alone, but from:
- Small-diameter tubing
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Long runs of restrictive emitter line
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Uphill sections
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Inline components that reduce flow
Parts included in BlueBarrel's Gravity-Fed Drip Irrigation Kit with Inline Emitters.
Water will continue moving until it encounters resistance. Good design minimizes those obstacles. As you plan your gravity-fed drip irrigation system, lay out your mainline to avoid uphill segments. The mainline can be laid out in a line, loop, grid, or forked pattern to bring flow to your entire garden. From the mainline, you will custom-place your pre-drilled emitter line, or individual bubbler emitters to deliver water to each plant (more detail on these components below).
Using Pre-Drilled Emitter Line
Emitter tubing (also called dripline) releases water at fixed intervals along its length. While convenient, it introduces resistance that limits how far water can travel in a gravity system.
For best performance:
- Follow maximum line lengths depending on emitter spacing
- Avoid compensating line
- Use the mainline to distribute water broadly, then branch into emitter sections
Max Line Lengths for Predrilled Emitterline
If using 1/4" predrilled emitterline, (like our Gravity-Fed Irrigation Kit with Inline Emitters, or the emitterline sold individually in our Online Store), mind maximum line-lengths to make sure plants at the end of the line get water.
Limit your line-lengths as follows:
- 6" emitter spacing: 16 feet per row
- 9" emitter spacing: 22 feet per row
- 12" emitter spacing: 28 feet per row
We also carry a Gravity-Fed Irrigation Kit with Bubbler Emitters. Bubbler emitters punch directly into the 1/2" irrigation mainline, and the ones we sell are individually adjustable for flow, so the distance restrictions are not as strict. (More on inline vs. bubbler emitters below under KEY COMPONENTS.)
EXPERT TIP: If you're on a flat site and using pre-drilled emitterline (recommended for veggie rows), plant the most water-loving plants closest to the water source, with more drought-tolerant plants farther away. Output will decrease farther down the line. (Watch our mid-season update video for more detail.) If you're using our custom-punch bubbler emitter kit (see below), you can twist each emitter to control the flow based on individual plant-needs. This is what we recommend for ornamental gardens.
Working With Slopes and Uneven Terrain
Gravity irrigation naturally favors downhill or level sites.
Uphill runs reduce flow and can stop it entirely if the water must climb above the water level in the barrels. However, small rises in the landscape are workable if the entire irrigation system remains below the water level.
Helpful guidelines:
- Keep the highest point of the irrigation line lower than the barrels
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Avoid routing tubing over ridges or raised obstacles if possible
On sloped properties, positioning barrels at the upper end of the garden can dramatically improve performance. For raised beds, consider drilling a hole to side-route the mainline directly at soil level.
Gravity-Friendly Components: 4 Steps to Success!
Most irrigation products are designed for household water pressure and may not perform well with gravity alone.
A gravity-fed system should use components that operate effectively at little or no pressure.
Here’s a barrel-to-garden supply list to get you started. All items available in our online store!
1. High-Flow Valves
While gravity will distribute water until it has nowhere else to go, you can minimize resistance by using full-port valves and fittings.
A standard 3/4" spigot has 3/4" threads on it, but the gate-valve or ball-valve inside standard offerings has a much narrower opening, often less than half an inch.
Use High-Flow Spigots and Drain Valves to head off your gravity-fed irrigation system with strong flow. These high-flow valves are included standard with our DIY RainKits®, and available for individual sale from our accessories menu.
Multiple drain valves can be used on larger systems to extend your irrigation area in all directions.
2. Streamlined Fine-Mesh Filters
A fine-mesh filter is essential for any drip irrigation system. You may be familiar with the large cartridge "Y filters" on standard drip manifolds. They are bulky and filter the water through an off-course loop, reducing the pressure more than you may want for your gravity-fed irrigation system.
For gravity-fed irrigation, we recommend a 100-micron Streamlined Drip Irrigation Filter. These are less expensive than Y filters, much smaller (a.k.a. better looking!), and they keep the water on a streamlined course to your drip-line.
3. Zero Pressure Automatic Timers
Automated timers offer the major convenience of a set-it-and-forget-it irrigation cycle. But there's a catch: standard irrigation timers require pressure to fully close. We've heard many stories from rainwater harvesters who set their timers and walked away, only to find their rain tanks empty and garden over-saturated the next morning.
Thankfully, there are timers made specifically for no- and low-pressure applications. BlueBarrel offers battery-operated no-pressure timers. The timer has two simple dials to set watering frequency and duration. (We used to carry a solar version, but over time these proved less reliable. We’ve tested many brands and now offer only the timer that we found works best.)
Watch our quick video tutorial on how to program and use this amazing no/low-pressure timer!
4. Non-Restricting Emitters & Soaker Hoses
Bubbler vs. Inline Emitters
BlueBarrel stocks two plug-and-play options for gravity-fed drip irrigation in our online store: one with inline emitters (for vegetables and row crops), and one with individually adjustable bubbler emitters (to control how much water each plant gets in an ornamental garden). Go to Tools & Accessories to see our full menu of supplies, and recommended uses for each kind of emitter kit. (The video below demonstrates how inline and bubbler emitters can be used together.)
Join Jesse in the garden again to see how inline and bubbler emitters can be combined for a customized gravity-fed drip irrigation setup.
Soaker Hoses
Soaker hoses have a porous surface that allows controlled amounts of water to seep out as water flows through. Weave a soaker hose through your garden and water will sink into the soil along the length of the hose.
Soaker hoses work wonderfully for shady perimeter gardens, hedge rows, or any layout where the hose can curve gently to serve every plant without a lot of exposure in between.
You can lay a soaker hose around tree trunks for the occasional deep watering that trees need. This perfectly targets the root-zone under the leaf line.
Click the image for a short video about irrigating with a no-pressure soaker hose. The next image shows this garden 5 weeks after planting!
A no-pressure soaker hose (specially for rain barrels) irrigates this new perimeter pollinator garden. See below for a video demoing how to set up a system like this.
What's special about a "rain barrel soaker hose?"
Like drip irrigation lines, most soaker hoses are designed to work optimally with standard water pressure. As rainwater harvesting grows in popularity, special soaker hoses have hit the market. BlueBarrel is proud to be one of the few vendors that offers No-Pressure Soaker Hoses specifically for rain barrels and rain tanks.
Rain barrel soaker hoses have a more porous wall so non-pressurized water can easily seep into your garden. Each hose is 50 feet long, and two hoses can be linked together for up to 100 linear feet of gravity-fed distribution.
EXPERT TIP: Rain barrel soaker hoses are prone to clogging for two reasons: (1) The pores are larger to compensate for non-pressurized water. This lets a little bit of sunlight in, which leads to algae growth. (2) One of the major benefits of irrigating with rainwater is that it isn't chlorinated. While your garden loves the organic matter in the water, hose pores can clog with prolonged exposure because there's no chlorine to combat the accumulation of algae and other particulates.
How to prevent clogs in a rain barrel soaker hose
For long-term use, soaker hoses perform best when kept fully shaded. Got a dense hedge-row? The soaker hose is perfect. Need a deep-watering aid for your trees? The soaker hose is your friend. When put away between uses, you won't have any problem.
If you do lay it out in the sun, you may notice the output declines over time. Flush out the pores with a blast of pressurized water and scrub the surface gently with a soft-bristled brush to restore the hose.
As with a standard drip system, always use a fine-mesh filter. Our Rain Barrel Soaker Hoses come with a 200-mesh filter—finer than the filters we sell for our Gravity Fed Drip Irrigation Kits—to help prevent clogs.
When Gravity Irrigation Systems do Best
Gravity irrigation shines in situations where simplicity, reliability, and water conservation are priorities.
Ideal applications include:
- Raised beds near the barrels
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Small to medium garden plots
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Drip irrigation zones*
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Off-grid watering
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Sites without convenient electrical access
Because there is no pump to fail and no electricity required, these systems can operate quietly and dependably for years.
*A gravity-fed drip line can be overlaid on to one or more "zones" of a pressurized drip manifold. Simply turn those zones off while you have rainwater, and back on when you run out!
When Gravity Alone May Not be Enough
While highly effective in many situations, gravity-fed systems have limitations.
You may need a pump if you want to:
- Run sprinklers
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Irrigate large landscapes
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Deliver water uphill
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Achieve high flow rates
In those cases, a hybrid approach—gravity storage with pumped distribution, or pumping to a relay tank that’s higher in the landscape—may be appropriate.
What Parts Don't I Need for Gravity Feed?
Typical pressurized drip systems require a few components that are not needed with gravity irrigation systems:
Pressure Reducers
Pressure reducers (a.k.a. pressure regulators) are a key component of pressurized drip irrigation systems. Municipal water is usually delivered at high pressure. When using city water, a pressure reducer brings PSI down to the 12-20 PSI range so you don't blow out your fittings.
With gravity-fed irrigation systems operating well below that pressure spec, you can completely forget about the pressure reducer.
Vacuum Breakers
Vacuum breakers (a.k.a. backflow preventers) prevent dirty water from being sucked back into the main in the event of a pressure reversal. When irrigating with city water, these are important for protecting the public drinking water supply.
When irrigating from rain barrels or tanks, you should not have a cross-connection with the municipal water system. There is no risk of your rain barrels sucking the water back in.
Watering Time
Following the basic principles from this article, you can successfully irrigate with very low pressure. On flat sites, you will get about 2 PSI from full rain barrels, approaching zero as the barrels empty.
While pressurized drip systems are spec’d for flow rates—usually noted as GPM (gallons per minute) or GPH (gallons per hour)—these ratings are based on consistent, standard water pressure. Your gravity-fed system runs on lower pressure, so you will likely need to leave the water on for longer to get the desired output.
Special irrigation timers are made for gravity-fed systems. See above for details.
Your drip line may have a 1 GPM (gallon per minute) rating, but a gravity fed line will take longer than a minute to emit one gallon. Experiment and observe to see how much water your plants really need.
EXPERT TIP: One benefit to slow water delivery is increased saturation efficiency. While you may think you’ll need to double your irrigation time, an extra 5-10 minutes may do the trick.
Still deciding whether gravity-feed will work in your situation? The answers below address the most common questions we answer about gravity-fed irrigation:
Frequently Asked Questions About Gravity Irrigation From Rain Barrels
How high do rain barrels need to be for gravity irrigation?
Most setups work best with barrels 2–10 feet above the irrigation area. More height means more pressure and better flow. That said, elevating barrels one foot or less can still work if the irrigation area is small and close to the barrels. You do not need pressure—you just need water to be able to flood the entire mainline.
Can rain barrels run sprinklers?
No. Sprinklers require much higher pressure than gravity can provide. Rain barrels pair best with drip irrigation or soaker hoses, which are much more efficient for your limited stored water anyway. A gravity-fed drip irrigation system offers a win-win.
Can you irrigate uphill from rain barrels?
No. Gravity systems work on level or down-sloping landscapes. Uphill watering requires a pump. Special consideration: If you have uphill segments in the irrigation line but the entire line remains lower than the rain barrels, a well-designed gravity-fed system can still function.
How far can gravity irrigation run from rain barrels?
Water can travel indefinitely through a properly sized mainline. Flow continues until it encounters resistance, such as an uphill section or restrictive tubing. While the mainline can cover a large layout, it is important to follow recommended lengths for pre-drilled emitter line. Ground-level rain barrels on flat sites often perform best within 20–50 feet, depending on micro-elevations and tubing size. Longer runs are possible if there are no small rises in the landscape.
Do I need special drip irrigation gear for gravity-fed systems?
Yes. Many drip components are designed for higher household pressure and will not work well with gravity alone. Gravity systems require no-to-low-pressure components that are compatible with gravity flow. See the article above for examples of gravity-friendly filters, timers, emitters, and more.
