Charles Austen QF Pressure Pond Filters
Compact pressurised UV filters in 10, 20 and 25 litre body sizes
The Charles Austen QF range gives you three sealed filter sizes: QF10, QF20 and QF25. They are intended for garden pond systems where the cleaned return needs to travel through hose to a waterfall or a point above the filter.
The number in the model name describes the filter-body size, not the pond volume and not the pump flow. QF10 is a 10 litre body with 7 W rated power, QF20 is 20 litres and 9 W, while QF25 is 25 litres and 11 W. The pump is selected separately to suit both the filter and the installed head.
A pressure filter is convenient, but no sealed canister is maintenance-free. Leave enough room for the lid, cleaning mechanism and hose connections, and never treat the largest marketing pond figure as suitable for a heavily stocked koi pond.
Compare the QF Filter Sizes
| Model | Filter body | Rated power | Best starting point |
|---|---|---|---|
| QF10 | 10 litres | 7 W | Small lightly stocked ponds |
| QF20 | 20 litres | 9 W | Medium garden ponds |
| QF25 | 25 litres | 11 W | Larger or more demanding duties |
Final sizing must use the current manufacturer pond-volume, fish-load and maximum-flow limits. A larger body normally offers more media and waste capacity, but it cannot compensate for an unsuitable pump or excessive stocking.
Match the Pump to the Filter
The pump must keep useful turnover without exceeding the QF unit’s permitted flow or pressure. Work from the pump performance curve at the real lift, then add pipe and fitting losses. A bypass or valve may help balance a system where the manufacturer permits it.
Use the largest practical hose bore and sweeping bends. Narrow corrugated hose can waste a surprising amount of pump output.
Cleaning and Seasonal Care
Backwashing or the built-in cleaning action removes loose waste, but the unit still needs periodic inspection. Check seals, UV sleeve, lamp, hose tails and biological media. Isolate both pump and UV before opening the lid.
Our advice: choose QF by actual workload, not by the number in its name. If you tell us the pond volume and fish, we can help with both filter and pump.
Related Categories and Spares
All pressure filters · Charles Austen G Series · Pond filter pumps · Pond pipework · UV bulbs
Frequently Asked Questions
What does QF10 mean?
It identifies the 10 litre filter-body model; it is not a 10,000 litre pond rating.
What are the three body sizes?
QF10 is 10 litres, QF20 is 20 litres and QF25 is 25 litres.
Which is the largest QF model?
QF25, with a 25 litre sealed body.
Is the pump included?
Treat pump selection as a separate compatibility check and confirm each product package before ordering.
Can a QF feed a waterfall?
A pressure filter can return water above its position, provided the chosen pump supplies enough real flow at the total head.
Can I exceed the maximum flow for better turnover?
No. Excess flow can reduce treatment time and exceed the unit’s limits.
Is a pressure filter good for koi?
Only when sized conservatively for the fish load. Many koi ponds need substantially more filtration.
Do QF filters need backwashing?
They require regular cleaning using the designed method, plus periodic inspection of the internal media and UV section.
Where should I put the filter?
On a stable, accessible base with space for hoses, cleaning and lid removal.
Can it be installed below water level?
Only in the orientations and level relationships permitted by the manufacturer instructions.
Why must I check the seals?
A pressure filter relies on sound O-rings and clamps to remain watertight.
Can I use narrow hose to make installation easier?
It may fit, but it increases friction and reduces delivered flow. Use the largest practical approved connection.
Does the filter make unsafe water safe automatically?
No. Test ammonia, nitrite, pH and other relevant parameters, especially while biological media matures.
How do I prepare it for winter?
Follow the manual, prevent trapped water from freezing and store vulnerable parts as instructed.
Can you size the pump and QF together?
Yes. Send pond volume, fish load, height difference, hose bore and run length.
