Garnet Filter Media
Garnet is the heaviest layer in a multimedia filter. Its high specific gravity keeps it at the bottom of the bed after every backwash, where its fine, dense grains capture particles that pass through the sand and anthracite above. We supply graded almandine garnet for municipal, industrial and mining filters, delivered from Johannesburg nationwide and across SADC.
Typical garnet filter media specification
| Property | Typical value |
|---|---|
| Mineral | Almandine garnet (iron aluminium silicate) |
| Specific gravity | 3.9 – 4.1 |
| Hardness (Mohs) | 7 – 7.5 |
| Grain shape | Sub-angular |
| Colour | Reddish-pink to brown |
| Fine filtration grades | 30/40 mesh (0.42 – 0.60 mm), 20/40 mesh (0.42 – 0.84 mm) |
| Support grades | 12/20 mesh (0.84 – 1.70 mm), 8/12 mesh (1.70 – 2.36 mm) |
Values are typical. A certificate of analysis is available per batch, and other gradings can be supplied to your specification.
Where garnet sits in a multimedia filter
| Layer (top to bottom) | Media | Role |
|---|---|---|
| 1 | Hydro anthracite | Coarse, light top layer that holds most of the solids load |
| 2 | Filter silica sand | Intermediate filtration |
| 3 | Fine garnet (30/40 or 20/40) | Polishing layer that removes the finest particles |
| 4 | Coarse garnet (8/12 or 12/20) | Prevents fine media migrating into the gravel |
| 5 | Support gravel | Supports the bed above the underdrain |
Applications
- Municipal drinking water multimedia filters
- Industrial pressure filters and process water
- Solvent extraction (SX) electrolyte filters in copper and cobalt plants
- Pre-treatment ahead of reverse osmosis and membranes
- Cooling tower side-stream filtration
Packaging and delivery
Supplied in bags and 1-ton bulk bags. Stock is held in Johannesburg with delivery to Pretoria, Cape Town, Durban and all provinces, and export to Botswana, Namibia, Zambia, the DRC and Mozambique.
Frequently asked questions
What is garnet filter media?
It is graded, washed garnet sand used as the dense bottom layer of multimedia filters. Because it is roughly 1.5 times heavier than silica sand, it stays below the sand after backwashing and keeps the bed layered correctly.
How deep should the garnet layer be?
Multimedia designs commonly use a fine garnet layer of about 75 – 100 mm over a coarse garnet layer of about 75 mm. Your filter designer or OEM specification takes priority.
Can I use garnet blasting abrasive in a water filter?
No. Blasting garnet is graded for cutting and may not be washed or sized for filtration. Use filter-grade garnet with a tight size range.
Do you supply complete multimedia beds?
Yes. We can supply anthracite, sand, garnet and gravel together, sized to your filter diameter and bed depths. Send us the filter drawing or dimensions for a quote.