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Gravity Feed vs Pumped Fuel Transfer:
Pros, Cons and What to Check
Gravity is free and never breaks down. It also never stops pushing, and that is most of the difference.
- Overhead Tanks
- Pumps
- Flow
- Control
Gravity feed runs diesel from a raised tank through a valve and hose using the height of the fuel alone, so it needs no power and has few moving parts. Its flow depends on the height of the fuel above the outlet, so it is lower than most pumps and drops as the tank empties, which limits filtering, metering and automatic nozzles. The outlet is always under pressure, so a valve left open or a failed hose keeps draining the tank, and an overhead tank is harder to fill and check. Pumped transfer adds a power supply and a pump to maintain, but gives a steady flow, works from a tank at ground level, stops when the pump stops, and suits a filter, meter and automatic nozzle. Tank outlets, valves and bunding can also be subject to AS 1940 and state rules, so check those for your site.
Overhead diesel tanks on stands are still a common sight on farms and older work sites. They are simple: open the valve and fuel runs out. Many sites now pump from a ground-level tank instead, and the reasons are mostly about control.
This guide compares the two on the things that matter day to day: flow, filtering and metering, nozzles, spill risk, access and power. Tank selection and storage compliance sit with the tank supplier, so this article keeps to the transfer equipment.
0 V Power a gravity-fed outlet needs
3.2 m Maximum tank height FuelGear's bottom fill kit is built for
50 L/min Listed flow of the ULTRAFLO 12V refuelling pump kit
10 micron Element in the farm tank filter, listed for gravity and pumped use
How They Work
How each one moves the fuel
Height does the work
Gravity feed
The tank sits on a stand above the equipment. Fuel leaves through a valve at the bottom and flows down the hose. The higher the fuel sits above the outlet, the more pressure there is behind it.
The pump does the work
Pumped transfer
The tank sits at ground level. A 12V, 24V or 240V pump draws fuel from it and pushes it through the filter, meter, hose and nozzle. Flow starts and stops with the pump.
Or by hand
Hand pumps
For drums and small volumes, a hand or rotary pump moves fuel with no power and no raised tank. The drum pumps guide covers the options.
Side by Side
Gravity feed and pumped transfer compared
| Point |
Gravity feed |
Pumped |
| Power |
None needed |
12V or 24V battery, or 240V mains |
| Flow |
Set by fuel height. Slower, and falls as the tank empties |
Set by the pump. Steady from full to nearly empty |
| Filtering |
Possible, but a filter slows an already low flow |
The pump pushes through the filter |
| Metering |
Low or changing flow can fall below a meter's rated range |
Steady flow suits a meter |
| Auto nozzle |
May not have the flow to work reliably |
Standard fit |
| When it stops |
Only when the valve is closed |
When the pump is switched off |
| Tank access |
Raised tank. Filling and dipping can mean a ladder |
Ground-level tank, filled and checked from the ground |
| Maintenance |
Valve, hose, stand and fittings |
The same, plus the pump and its wiring |
Flow
Why gravity flow is slow, and gets slower
The only thing pushing fuel out of a gravity-fed tank is the weight of the fuel above the outlet. A full tank on a tall stand pushes harder than a nearly empty one. So flow is at its best when the tank is full and drops steadily as it empties.
Everything in the line takes some of that small pressure away. A long or narrow hose, a filter, a meter and the nozzle all add resistance. On a pumped setup, the pump makes up for it. On a gravity setup, nothing does, and the flow at the nozzle can end up well below what the hose size suggests.
Automatic nozzles need flow
An automatic nozzle uses the flow through it to sense when the tank is full and shut off. At low flow it may not trip reliably. If you do run an automatic nozzle on gravity, check its minimum flow against what the tank delivers when it is low. Automatic vs manual fuel nozzles explains how the shut-off works.
Control
The outlet that never switches off
On a gravity-fed tank, the valve and everything after it are under pressure for as long as there is fuel in the tank. That has practical consequences.
- A valve left open keeps running. There is no pump to switch off, so an unattended fill can drain the tank onto the ground.
- A failed hose keeps leaking. A split hose or loose fitting below the valve leaks until someone closes it.
- Access is harder to control. Anyone who can reach the valve can draw fuel. A pump can be isolated, locked out or run through a fuel management system.
A pumped setup stops when the pump stops. That does not remove the need for a sound hose and nozzle, but it limits how much fuel a mistake can cost.
Access
Filling and checking a raised tank
An overhead tank is fine to draw from but awkward to fill and dip. The fill point and the level are at the top, which can mean a ladder for the delivery driver and whoever checks the level.
FuelGear's diesel tank bottom fill kit brings the fill point and a sight tube down to ground level. It is listed for horizontal or tripod overhead tanks up to 3.2 m high, with fill terminals no more than 200 mm from the tank edge, and includes the sight tube, fittings, valves, camlocks, a galvanised pipe fill point and a stand-alone vent. It comes in 1 1/2 inch, 1 1/4 inch and 2 inch sizes.
Keeping Gravity
If you are keeping a gravity-fed tank
Plenty of overhead tanks have years left in them. These make one safer and cleaner to use.
- Fit a filter. The farm tank filter is listed for gravity, hand, air or electric pump use, with a 10 micron element, drain valve and replaceable bowl. Expect it to slow the flow.
- Use a manual nozzle you hold open. It closes the moment it is let go.
- Keep the valve closed between fills, and make that the habit for everyone who uses it.
- Use hose rated for diesel and replace it when it cracks or hardens. See fuel hoses: ratings, diameters and when to replace them.
- Let the tank breathe. A blocked vent slows the flow as the tank empties. A filtered breather keeps dust and moisture out.
- Check the stand. Rust, lean or soft footings under a full tank are a serious hazard.
Going Pumped
Moving to a pumped setup
A ground-level tank with a pump suits sites that want a steady flow, a filter and meter that work properly, an automatic nozzle and tighter control over who draws fuel.
- Pick the power. 12V or 24V where the tank is near a vehicle or battery, 240V where there is mains power. 12V vs 24V vs 240V diesel transfer pumps compares them.
- Size the flow. The diesel transfer pump buying guide matches the pump to the job.
- Add the rest of the line. A filter, a meter and an automatic nozzle complete it. How to set up a farm refuelling station works through it in order.
- Or start from a kit. The ULTRAFLO 12V refuelling pump kit comes with the pump, hose, automatic nozzle and a suction filter.
Rules
Check the rules for your site
How a diesel tank is stored, bunded and fitted with outlets and valves can be covered by AS 1940, state and territory dangerous goods and environment rules, and your own site or insurer's requirements. These differ by location and by the size of the tank. Before installing or changing a gravity-fed tank, check what applies with your state regulator or tank supplier.
Summary
Simple versus controlled
Gravity feed needs no power and has few parts, but its flow is low and falls as the tank empties, it limits filtering, metering and automatic nozzles, and the outlet stays under pressure until the valve is closed. Pumped transfer needs power and a pump to maintain, but gives a steady flow from a ground-level tank, suits a filter, meter and automatic nozzle, and stops when the pump stops. If you keep a gravity-fed tank, filter it, close the valve between fills, use a manual nozzle and bring filling and dipping down to the ground.
FAQ
Frequently asked questions
Is a gravity-fed diesel tank better than a pumped one?
Neither is better for every site. Gravity feed needs no power and has few parts. Pumped transfer gives a steady flow, suits a filter, meter and automatic nozzle, works from a ground-level tank and stops when the pump stops. Most sites that want control and metering choose a pump.
Why is my gravity-fed diesel tank flowing slowly?
Gravity flow depends on the height of the fuel above the outlet, so it falls as the tank empties. A blocked filter, a narrow or long hose, a partly closed valve or a blocked tank vent slow it further. Check the vent and the filter first.
Can I use an automatic nozzle on a gravity-fed tank?
An automatic nozzle relies on flow to trip its shut-off, so at low flow it may not work reliably. Check the nozzle's minimum flow against what the tank delivers when it is low. Many gravity setups use a manual nozzle instead.
Can you put a filter on a gravity-fed fuel tank?
Yes. FuelGear's farm tank filter is listed for gravity, hand, air and electric pump use. It will reduce the flow, because gravity has less pressure to push fuel through the element than a pump does.
How do I fill an overhead diesel tank from the ground?
A bottom fill kit runs a fill pipe and sight tube down the side of the tank, so it can be filled and its level checked from the ground. FuelGear's kit is listed for horizontal or tripod tanks up to 3.2 m high.
Are gravity-fed fuel tanks legal?
That depends on the tank, the site and where you are. Storage, bunding, outlets and valves can be covered by AS 1940 and state and territory rules. Check with your state regulator or tank supplier before installing or changing one.
Gravity or pumped, we'll fit it out
FuelGear stocks fuel transfer pumps and kits, filtration, tank fittings and bottom fill kits and nozzles. Tell us about the tank and how you use it, and we will put the setup together.