Pureflow Bio · 6 catalogue models
Gravity Feed Combi Drum Filters
Gravity-fed combi filtration with automatic drum screening and biological treatment chambers. Compare six GCRDF models from 10 to 100 m³/h catalogue maximum flow, with model-specific inlet, outlet and UV listings.
Download the series catalogue (PDF) ↗
Choose your Gravity Feed CRDF model
10 m³/h · 30 W × 2 UV
GCRDF-10
Gravity-fed combi filtration for koi ponds and small recirculating systems, with a 10 m³/h catalogue maximum-flow listing.
View GCRDF-10 details →
15 m³/h · 40 W × 2 UV
GCRDF-15
Gravity-fed combi filtration for koi ponds and small recirculating systems, with a 15 m³/h catalogue maximum-flow listing.
View GCRDF-15 details →25 m³/h · 60 W × 2 UV
GCRDF-25
Gravity-fed combi filtration for larger koi ponds and nursery filter circuits, with a 25 m³/h catalogue maximum-flow listing.
Shared Gravity series illustration.
View GCRDF-25 details →35 m³/h · 60 W × 3 UV
GCRDF-35
Gravity-fed combi filtration for larger koi ponds and nursery filter circuits, with a 35 m³/h catalogue maximum-flow listing.
Shared Gravity series illustration.
View GCRDF-35 details →50 m³/h · 60 W × 4 UV
GCRDF-50
Gravity-fed combi filtration for fish-farm and hatchery treatment circuits, with a 50 m³/h catalogue maximum-flow listing.
Shared Gravity series illustration.
View GCRDF-50 details →
100 m³/h · 80 W × 3 UV
GCRDF-100
Gravity-fed combi filtration for fish-farm and hatchery treatment circuits, with a 100 m³/h catalogue maximum-flow listing.
View GCRDF-100 details →Gravity Feed CRDF technical comparison
| Model | L × W × H (mm) | Listed water volume (m³) | Max. flow (m³/h) | Inlet (mm × qty) | Outlet (mm × qty) | UV lamp listing |
|---|---|---|---|---|---|---|
| GCRDF-10 | 1200 × 650 × 550 | 10 | 10 | 75 × 3 | 50 × 2 | 30 W × 2 |
| GCRDF-15 | 1200 × 900 × 750 | 15 | 15 | 90 × 3 | 75 × 2 | 40 W × 2 |
| GCRDF-25 | 1450 × 950 × 750 | 25 | 25 | 110 × 4 | 90 × 3 | 60 W × 2 |
| GCRDF-35 | 1600 × pending × 900 | 35 | 35 | 110 × 5 | 110 × 3 | 60 W × 3 |
| GCRDF-50 | 2050 × 1050 × 1000 | 50 | 50 | 110 × 6 | 110 × 3 | 60 W × 4 |
| GCRDF-100 | 2690 × 1450 × 1000 | 100 | 100 | 160 × 5 | 110 × 3 | 80 W × 3 |
GCRDF-35 width: pending confirmation. Dimensional verification is deferred; obtain the approved drawing before setting installation dimensions. The original catalogue entry is not an approved installation width.
Catalogue maximum flow and listed water volume are comparison values. Final selection also depends on solids and feed loading, biological media, aeration and available hydraulic head. UV listings show watts per lamp × quantity; they are not the total electrical load or a validated disinfection dose.
Plan the Gravity Feed CRDF installation
Water reaches the filter by gravity through the planned pond or system connections. Drum screening removes retained solids before the biological stage. Coordinate the filter operating level and the downstream return-pump arrangement so the hydraulic path works at both clean-screen and loaded-screen conditions.
Set the filter operating level against the pond water level and approved drawing. Review pipe friction, clean-to-dirty-side water-level difference, pump-stop behaviour and safe overflow provision. Leave access to the screen, wash pump, UV equipment and biological chambers.
Hydraulics
Check peak filter flow, operating water levels, pipe friction and pump-stop behaviour.
Biological treatment
Review the media, aeration and feed-load basis independently of the catalogue water-volume listing.
Utilities and service
Provide wash water, drainage, electrical isolation and space to maintain the drum, pumps and UV lamps.
Series construction and arrangement
Gravity Feed CRDF FAQs
What is a gravity-fed combi drum filter?
It is a combi filter installed at pond water level and fed by bottom drains and skimmers. Water flows into it by gravity, so waste arrives whole, and the pump sits after the filter, handling only clean water.
Which models are in the Gravity Feed range?
There are six: GCRDF-10, GCRDF-15, GCRDF-25, GCRDF-35, GCRDF-50 and GCRDF-100. The number is the maximum flow in m³/h.
Do I need a bottom drain for gravity feed?
Yes. Gravity feed works with one or more bottom drains, and usually a skimmer, piped to the filter. It's best planned when the pond is being built, because the filter has to sit with its water level matching the pond.
Why do koi keepers prefer gravity-fed filtration?
Waste goes straight from the pond floor to the screen without passing through a pump, so it isn't chopped into fine particles that cloud the water. The pump and UV only ever see filtered water, which means less wear and less cleaning.
Can a gravity system overflow if the drum stops?
If the screen blocks completely, water backs up into the filter chamber. That's why we recommend an overflow or bypass and a reliable power supply for the wash pump, and you should check it during routine visits.
Request a Gravity Feed CRDF quotation
Share your filter flow, application, daily feed and project location. Our team will review the equipment and installation requirements with you.