Charles Austen L Series High-Head Pond Pumps
Powerful 12,000 to 25,000 l/h pumps for elevated returns, large waterfalls and aquaculture systems
The L Series is the high-head family for serious water movement. It starts at 12,000 l/h with a 5 m maximum head and rises to 25,000 l/h with 9.5 m. These figures suit high waterfalls, elevated filter rooms and aquaculture circulation where a low-head pump would lose most of its output.
The trade-off is power: published inputs range from 160 to 620 W. L Series makes sense when the system genuinely needs pressure, not simply because the pond is large.
A high-head pump deserves proper pressure-capable pipework, isolation and a performance-curve check at the designed duty.
Model Comparison
| Model | Maximum flow | Maximum head | Power |
|---|---|---|---|
| L12 | 12,000 l/h | 5.0 m | 160 W |
| L15 | 15,000 l/h | 5.4 m | 265 W |
| L18 | 18,000 l/h | 6.5 m | 325 W |
| L20 | 20,000 l/h | 6.7 m | 400 W |
| L23 | 23,000 l/h | 8.5 m | 520 W |
| L25 | 25,000 l/h | 9.5 m | 620 W |
Maximum figures compare the models. Real flow falls as lift, pipe friction and connected equipment add resistance.
Where high head is worth paying for
Use L Series when the return rises several metres, when a pressure-hungry nozzle is specified or when long pipework and equipment create significant resistance. It is excessive for a short low-level filter return.
Compare electricity at the real operating point over a full year, not only the purchase price.
Pipework and protection
Use pressure-rated pipe and fittings of adequate bore. Include unions, isolation and a non-return arrangement only where appropriate to the system design. Avoid a small hose tail that wastes the pump pressure as friction.
Large pumps can empty chambers or create strong suction; protect livestock and maintain the minimum operating water level.
Specify the duty point
Calculate static lift and estimated friction, then choose the model whose curve passes through the required flow. Maximum-flow and maximum-head endpoints are not a duty point.
Our advice: send us the drawing before ordering an L Series pump. At these power levels, a sizing mistake is expensive every day it runs.
Related Pump and Installation Categories
Charles Austen pump families · All pond pumps · Commercial pond and lake pumps · Pressure pipework
Frequently Asked Questions
Which L Series model has the highest head?
L25, at a published maximum head of 9.5 m.
Can I use L Series on a low-level filter return?
You can, but the power and pressure may be unnecessary; compare a lower-head efficient pump.
Are these for large waterfalls?
Yes, where the selected curve delivers the required width and depth at the full lift.
Why is the wattage high?
High pressure and high flow require more input power than a low-head circulation duty.
Can I use flexible pond hose?
For a high-head permanent installation, properly sized pressure-rated rigid pipe is usually preferable.
Can L Series serve aquaculture?
Yes, subject to correct duty, livestock protection and installation.
Is L25 twice as powerful as L12?
It has higher flow, head and power input; compare the actual curves rather than a simple ratio.
Do I need a non-return valve?
Only where the system design requires it; every valve adds resistance and must be accessible.
Does maximum flow tell me what reaches the outlet?
No. Maximum flow is measured at little or no head. Lift, pipe length, fittings and connected equipment reduce delivered flow.
Is maximum head the height for full flow?
No. It is the shut-off end of the curve, where useful flow approaches zero.
Should I use the largest practical pipe bore?
Yes. Generous, smooth pipework usually improves real flow and efficiency.
Can I throttle the pump with a valve?
Where permitted, a valve can trim flow, but heavy throttling wastes performance. Correct sizing or approved electronic control is preferable.
How often should the pump be cleaned?
Inspect and clean the intake and impeller whenever output falls and during routine pond maintenance.
Can you help me choose the model?
Yes. Send us the desired flow, vertical lift, pipe bore and length, fittings and connected filter or feature.
Why is my flow lower than the model name?
The model figure is a maximum comparison point, not the delivered flow through a real installation.
