An airlift pump does two jobs with one air supply: it moves water and aerates it at the same time, with no submerged motor or impeller. In a RAS that makes it a clean, reliable way to circulate water between tanks, biofilters and sumps. The catch is sizing the blower — airlift air demand is set by submergence depth, lift height and the flow you want, and the blower must deliver that air at the pressure of the submergence. A single-stage YEBL-1 suits shallow lifts; deeper submergence moves you to a double-stage YEBL-DS.
How an airlift works
Air injected at the foot of a vertical pipe makes the air-water mixture inside lighter than the surrounding water, so the column rises and carries water up and out. Two geometry terms govern it:
- Submergence — how deep the air injection point sits below the water surface. This sets the pressure the blower must overcome.
- Lift — how far above the surface you raise the water. Higher lift needs more air at higher submergence to work well.
The beauty of the airlift is what it lacks: no moving parts in the water, nothing to seize, and the same air that lifts the water also oxygenates it.
What sets the air demand
Airlift efficiency depends on the submergence ratio — submergence divided by total lift. A higher submergence ratio (the injection point well below the surface relative to the lift) moves water with less air. Low submergence with high lift is air-hungry and inefficient.
| Design condition | Air demand | Blower pressure need |
|---|---|---|
| High submergence, low lift | Low air per m³ water | Set by submergence depth |
| Moderate submergence + lift | Moderate air | Higher |
| Low submergence, high lift | High air, inefficient | Highest — avoid |
Because deeper injection means higher back-pressure, a deep-sump airlift can demand the 300–500 mbar band that belongs to a double-stage YEBL-DS. Design for a healthy submergence ratio and you keep both air demand and energy sensible.
Sizing the blower — worked example
A RAS uses six airlifts to circulate water, each injecting air at ~1.8 m submergence and moving water up ~0.4 m, each needing ~25 m³/hr of air:
- Airflow: 6 × 25 = 150 m³/hr
- Pressure: ~1.8 m submergence + line losses ≈ 220–260 mbar
- Match: YEBL-1-270 (3 HP, 270 m³/hr, 250 mbar), with a standby.
If the same airlifts sat at 2.4 m submergence in a deep sump, pressure would climb past 300 mbar and the pick becomes a YEBL-DS-230 (4 HP, 230 m³/hr, 410 mbar).
| Airlift set | Submergence | Total air | Model | Family |
|---|---|---|---|---|
| 4 lifts | 1.5 m | ~80 m³/hr | YEBL-1-145 1 HP | single stage |
| 6 lifts | 1.8 m | ~150 m³/hr | YEBL-1-270 3 HP | single stage |
| 6 lifts | 2.4 m | ~150 m³/hr | YEBL-DS-230 4 HP | double stage |
Don't forget the tanks
In a real RAS the airlift air is only part of the total — you still add culture-tank oxygenation, biofilter fluidisation and degassing. Size the blower to the sum of every air user at the deepest pressure, exactly as in RAS aeration blower selection. The general pressure-and-airflow method is in sizing an air blower for biofloc tanks, and the DO strategy behind it in dissolved oxygen management with blowers.
Reliability
Airlifts are the water circulation in a RAS, so if the blower stops, water stops moving and DO falls. That doubles the case for a duty-standby pair on auto-changeover and backed power. The whole-system view is in the biofloc aeration pillar guide.
Why farms choose airlifts
Airlifts trade a little energy efficiency for a lot of reliability and gentleness, which is often the right trade in aquaculture:
- No moving parts in the water — nothing to seize, corrode or entangle, and no submerged motor to fail.
- Gentle on stock — they move water in a slow, low-shear flow that does not batter eggs, larvae or delicate fish.
- Dual purpose — the same air lifts the water and oxygenates it, so one blower does circulation and aeration together.
- Simple redundancy — because the only machine is the onshore blower, a standby blower backs up the entire water movement.
The efficiency cost is real — a centrifugal pump moves water with less energy per m³ — but for low-head recirculation the airlift's simplicity and gentleness usually win.
Design tips for efficient airlifts
- Maximise submergence relative to lift. A higher submergence ratio moves water with far less air — the single biggest efficiency lever.
- Keep the lift low. Airlifts shine at low head; asking one to lift high is air-hungry and wasteful.
- Size the riser diameter to the flow you want, and feed each airlift from a balanced header so all deliver evenly.
- Fit a footvalve or check so the loop does not drain back into the blower on shutdown.
Airlift vs pump: an honest comparison
It is worth being clear-eyed about the trade-off, because airlifts are not always the right answer.
| Factor | Airlift (blower-driven) | Centrifugal water pump |
|---|---|---|
| Energy per m³ of water | Higher | Lower |
| Head capability | Low head only | High head available |
| Aeration bonus | Yes — aerates as it lifts | No |
| Moving parts in water | None | Impeller, seal |
| Gentleness on stock | Very gentle, low shear | Higher shear |
| Reliability / redundancy | Onshore blower + standby | Pump + standby pump |
For low-head recirculation of sensitive stock, the airlift's gentleness, aeration bonus and lack of in-water machinery usually outweigh its lower energy efficiency. For high-head or long-distance water movement, a pump is the right tool and the blower is reserved for aeration and biofilter duty. Many well-designed RAS use both — airlifts for the gentle internal recirculation, a pump only where real head is needed.
Frequently asked questions
How much air does an airlift pump need?
It depends on submergence, lift and target flow, but a healthy submergence ratio keeps it modest — often ~20–30 m³/hr of air per airlift in a typical RAS. Design for high submergence and low lift.
What pressure blower do airlifts need?
Enough to overcome the injection submergence — roughly 100 mbar per metre plus line losses. Shallow lifts suit a single-stage YEBL-1; deep sumps need a double-stage YEBL-DS.
Can one blower run airlifts and aeration?
Yes — airlift air is just one more user in the RAS total, sized alongside tanks, biofilter and degasser as in RAS aeration blower selection.
See the aquaculture and biofloc application page for the range.
In summary
An airlift moves water and aerates it at once, with no submerged motor and no moving parts in the water — gentle on stock and simple to make redundant behind an onshore blower. Its air demand is governed by submergence and lift: design for a healthy submergence ratio (injection well below the surface relative to the lift) and the air demand and energy stay sensible; ask an airlift for high lift on low submergence and it becomes air-hungry and inefficient. Size the blower to overcome the injection depth — ~100 mbar/m plus losses — so shallow lifts suit a single-stage YEBL-1 and deep sumps a double-stage YEBL-DS. Remember the airlift air is only one user in the RAS total, added to tanks, biofilter and degasser. And because the airlift is your water circulation, a stopped blower stops both flow and oxygen — so a tested standby is essential.
Talk to an engineer
Send your airlift count, submergence and target flow and we will size the blower plus standby. WhatsApp +91 9311693322 or email sales@yashblowers.org — Faridabad, quoted within 24 hours.