Although its potential for water treatment has been recognized since ancient times, anthracite coal was not used for this purpose until the beginning of the
20th century. Crushed Anthracite makes an excellent medium density filtration
media. Clack Anthracite is mined from the finest Pennsylvania coal. It is specifically selected for water treatment, and during its production goes through several sizing inspections. Representative samples
are randomly chosen for a complete laboratory quality control analysis for
effective size, uniformity coefficient,
specific gravity, acid solubility and
Because of its angular shape, some of the sediment penetrates deeper into the bed.
When compared to equivalent filter sands, this means longer filter runs and less head
loss. Backwash rates are also reduced. Because of its unique density, Clack
Anthracite can be used in multi-media filters. At 50 lbs/ft³, it will hydraulically
classify and remain above heavier media such as Filter Sand or Manganese
Greensand, providing a prefiltration layer.


• Higher service flows and longer filter runs than equivalent sand filters
• Close attention to gradation,
hardness and purity assures consistent and reliable performance
• Unique density allows Clack Anthracite to be combined with
other filtration media in multi-media filters
• Lower uniformity coefficient has less oversized and undersized particles resulting in a highly uniform bed
• Color: Black
• Bulk Density: 50 lbs./cu. ft.
• Hardness: 3.0-3.8 (Mohs scale)
• Effective Size:
#1 Anthracite: 0.6-0.8 mm
#1½ Anthracite: 0.85-0.95 mm
#2 Anthracite: 1.7-2.0 mm
• Uniformity Coefficient:
#1 Anthracite: <1.7
#1½ Anthracite: <1.7
#2 Anthracite: <1.6
• Mesh Size:
#1 Anthracite: 14×30
#1½ Anthracite: 10×20
#2 Anthracite: 4×12
• Acid Solubility: <1%
• Caustic Solubility: <1%
• Apparent Specific Gravity: 1.6 gm/cc • Meets AWWA Standard B100-01
• Bed depth: 24-36 in., 10-18 in multibed filters
• Freeboard: 50% of bed depth (min.)
• Service flow rate: 5 gpm/sq. ft.
or higher depending upon local conditions
• Backwash flow rate:
#1 Anthracite: 12-18 gpm/sq. ft.
#1½ Anthracite: 18-25 gpm/sq. ft.
#2 Anthracite: use air scour
• Backwash bed expansion: 20-40%  of bed depth