Gravity Fed Systems: Raised Reservoir & Off-Grid SetupsUpdated 2 months ago
Who This Is For
Gravity fed Blumat systems are for anyone who doesn't have a hose bib nearby — or prefers a completely off-grid, no-electricity, no-pressure setup. Water pressure comes entirely from elevation: raise a bucket or reservoir above your plants, and gravity does the rest.
Common uses: backyard gardens without nearby water access, patios and balconies, rainwater collection systems, small outdoor container gardens, off-grid growing, and growers who want the simplest possible setup.
How Gravity Creates Pressure
Every 2 feet 4 inches of elevation = approximately 1 PSI.
Blumat sensors need at least 1 PSI to function. That means your reservoir water surface needs to be at least 3 feet above the sensors to operate reliably. For BluSoak 2.0 drip tape, aim for 3.5 feet minimum (1.5 PSI).
Even at 12 feet of elevation you stay safely within the Blumat operating range — no pressure reducer needed unless you're above 15 PSI (about 35 feet of head height).
What You Need
1. Reservoir
Any clean container works — a 5-gallon bucket is the classic choice. Install a bulkhead fitting through the side or bottom to connect your 8mm supply line. Size the reservoir for your duration between refills: most plants use ¼ to 1 liter per week depending on size and conditions.
2. Supply Line
8mm tubing runs from the bulkhead fitting to your growing area. For more than a few plants or longer runs, use a looping layout (two bulkhead fittings — one supply, one return) to increase flow and build redundancy.
3. Sensors
Standard 5" or 9" Tropf sensors. Gravity systems use the same sensors as pressurized — just set to the gold mark on preset sensors, or calibrated using the hanging drip method on standard sensors.
4. Distribution
At gravity pressures (1–5 PSI), your distribution options are:
- Basic drippers — work at any pressure above 1 PSI
- Drip rings — work at any pressure above 1 PSI
- BluSoak 2.0 — designed for gravity, works down to 1.5 PSI. Fold the end over to seal.
- BluSoak 1.0 — requires at least 2 PSI, so raise the reservoir to at least 4.5 feet
- BluSoak 3.0 — not suitable for gravity systems, requires 12–15 PSI
Air Purging — Critical for Gravity Systems
This is the most common gravity system problem. At low pressures, even a small air bubble in the supply line can completely stop water flow. Install a ball valve or flush valve at the far end of your supply line. If your reservoir runs dry:
- Refill the reservoir
- Open the flush valve at the end of the line
- Wait until water runs steadily with no sputtering
- Close the valve — system resumes normally
Looping Layout for Better Performance
A single-exit bucket limits total flow. For more than ~5 sensors on gravity, use the two-bulkhead loop method:
- Install two bulkhead fittings in your reservoir
- Run tubing out of the first, through your growing area, and back into the second
- Water flows in both directions — doubles flow capacity and adds redundancy
- If one side clogs, the other side still feeds all sensors
Gravity vs Pressurized — When to Switch
Gravity systems are excellent for small to medium setups. Consider switching to a pressurized system or pump kit if:
- You have more than 15–20 sensors and are seeing uneven watering at the far end
- You can't raise the reservoir high enough for adequate pressure
- You want to use BluSoak 3.0 or need higher-pressure distribution
- You're tired of refilling the reservoir and want automatic top-off
📖 Pressurized Systems: Backyard Gardens, Grow Tents & Indoor Grows