AFM Grade 1, Activated Filter Media, 25 kg
Glass that filters finer than sand and never needs replacing.
Activated filter media grade 1, 0.4 to 1 mm, 25 kg. Made from activated recycled glass, it filters to about 4 micron without a coagulant, resists the biofilm that turns a sand bed into a colony, and backwashes with a third less water. The top layer of an AFM vessel; grade 2 goes underneath.
Vessel, valve and media together: the complete kitsWhy glass beats sand
Sand filters grow biofilm. Within months the grains are coated, the bed channels, and bacteria colonise the filter that was meant to remove them. Activated filter media is made from recycled glass with a surface that resists biofilm and carries a slight charge, so it filters finer than sand (about 4 micron without a coagulant), never needs replacing, and backwashes with a third less water because it is lighter and rinses clean.
How much to buy
| Vessel | Grade 1 | Grade 2 underneath |
|---|---|---|
| 45 L vessel | 1 bag | 1 bag |
| 75 L vessel (ours) | 2 bags | 1 bag |
| 100 L vessel | 3 bags | 1 bag |
Grade 2 forms the coarse support layer around the bottom strainer; grade 1 does the filtering above it.
Backwashing
Weekly, or when the pressure across the vessel rises 0.5 bar, at about 40 metres an hour: 50 litres a minute in our 75 litre vessel. The bed should lift 20 to 40%, which is why the vessel is filled to 75 litres and not to the neck. Twelve to fifteen minutes, then a two-minute rinse.
Life
Ten years or more. It does not wear, dissolve or rot; the only reason to take it out is to move the vessel.
Before you buy.
Goes with it.
Whole shopAFM Grade 2, Activated Filter Media, 25 kg
The coarse layer under grade 1. Or the whole bed at high flow.
Riser and distributors included75 Litre FRP Vessel with Riser and Distributors
The tank a filter or softener is built in. With the parts everyone else sells separately.
Free courierRunxin F67C1 Automatic Filter Valve
Backwashes itself. Set the days, set the hour, forget it.