The layers that keep the bed where it belongs
Support Gravel
Rounded, washed silica gravel in graded layers that support the filter media above the underdrain and distribute backwash flow evenly across the bed.
- Manufactured to: EN 12904
- Manufactured to: AWWA B100
Overview
Support gravel does two jobs at once: it stops filter sand from migrating into the underdrain, and it spreads backwash water evenly so the bed fluidises uniformly instead of channelling. Both jobs depend on the layer gradations being correct relative to each other and to the media above.
We supply the full layer set — typically four gradations from 2–4 mm up to 16–32 mm — so the 1:4 size progression between adjacent layers is maintained. Each size is washed free of fines and supplied dry, with the sieve analysis for the specific lot.
Packing options
- Woven polypropylene bag25 kg / 50 kg
- Jumbo bag (FIBC)1,000 kg / 1,500 kg
- Bulk—
Available gradations
Support Gravel
| Size | Typical use |
|---|---|
| 2 – 4 mm | Top support layer, directly beneath the sand |
| 4 – 8 mm | Second transition layer |
| 8 – 16 mm | Third layer |
| 16 – 32 mm | Bottom layer, over the underdrain / nozzle plate |
- Size
- 2 – 4 mm
- Typical use
- Top support layer, directly beneath the sand
- Size
- 4 – 8 mm
- Typical use
- Second transition layer
- Size
- 8 – 16 mm
- Typical use
- Third layer
- Size
- 16 – 32 mm
- Typical use
- Bottom layer, over the underdrain / nozzle plate
Other cuts can be produced to specification — send us the effective size and uniformity coefficient you need.
Technical specification
| Property | Typical value | Test method |
|---|---|---|
| Silica content (SiO₂) | ≥ 96% | XRF |
| Acid solubility (HCl) | ≤ 2.0% | EN 12902 |
| Specific gravity | 2.60 – 2.68 g/cm³ | — |
| Grain shape | Rounded to sub-rounded | — |
| Fines content | ≤ 1% | — |
- Property
- Silica content (SiO₂)
- Typical value
- ≥ 96%
- Test method
- XRF
- Property
- Acid solubility (HCl)
- Typical value
- ≤ 2.0%
- Test method
- EN 12902
- Property
- Specific gravity
- Typical value
- 2.60 – 2.68 g/cm³
- Test method
- —
- Property
- Grain shape
- Typical value
- Rounded to sub-rounded
- Test method
- —
- Property
- Fines content
- Typical value
- ≤ 1%
- Test method
- —
Typical values. The certificate issued with your shipment reports the figures measured on that production lot.
Where it is used
Municipal Water Treatment
Rapid gravity and pressure filters producing potable water for towns and cities.
Desalination Plants
Pre-treatment filtration protecting SWRO membranes from suspended solids and biofouling.
Industrial Water
Process, cooling and boiler feed water filtration across manufacturing sites.
Wastewater Treatment
Tertiary filtration and effluent polishing ahead of discharge or reuse.
Water Wells & Gravel Packs
Graded gravel packs around well screens controlling sand ingress and yield.
Related products
Need this grade?
Send the gradation, the volume and the destination port. Our technical team responds within one working day with pricing, lead time and a specimen certificate of analysis.