Calculator 1 of 4
Media Filter Sizing
Size gravity or pressure media filters based on design flow rate and hydraulic loading rate. Results feed directly into the Backwash calculator below.
| Media Type | Typical HLR | Max HLR |
|---|---|---|
| Pressure Sand | 3–6 GPM/ft² | 8 GPM/ft² |
| Dual Media (Anthracite/Sand) | 4–8 GPM/ft² | 12 GPM/ft² |
| Multi-Media (Anthracite/Sand/Garnet) | 4–8 GPM/ft² | 12 GPM/ft² |
| Greensand (Mn-treated) | 2–4 GPM/ft² | 5 GPM/ft² |
Inputs
Results
Total filter area
A_total = Q / HLR
Area per vessel
A_vessel = A_total / n_vessels
Theoretical vessel diameter
D_calc = √(4 × A_vessel / π) — rounded UP to nearest standard size (18", 24", 30", 36", 42", 48", 54", 60", 72", 84")
Actual area per vessel
A_actual = π/4 × (D/12)² where D is in inches
Actual HLR at design flow
HLR_actual = Q / (n_vessels × A_actual)
Media volume per vessel at 24" bed depth
V_media = A_actual × 2 ft
Calculator 2 of 4
Backwash Rate & Duration
Calculate backwash flow for target bed expansion, duration, and total water volume. Temperature correction for viscosity is applied automatically.
Inputs
Results
Standard BW rates at 30% expansion, 60°F
- Sand (0.5mm): 12 GPM/ft²
- Anthracite (1.0mm): 8 GPM/ft²
- Garnet (0.35mm): 15 GPM/ft²
- Mixed/Dual media: 10 GPM/ft²
Temperature viscosity correction
µ(T) = 2.414×10⁻⁵ × 10^(247.8/(T_K − 140)) cP, where T_K = (T_°F − 32)/1.8 + 273.15
CF_visc = (µ(T) / µ(60°F))^0.22
Expansion-adjusted BW rate
BW_rate = (BW_30pct / CF_visc) × (target_expansion / 30)
Expanded bed depth & freeboard
expanded_depth = settled_depth × (1 + target_expansion/100)
freeboard_min = (expanded_depth − settled_depth) + 6"
Flow and volume
BW_flow = BW_rate × (π/4) × (D_in/12)²
BW_volume = BW_flow × duration_min
Calculator 3 of 4
Cartridge Filter Sizing
Determine the number of cartridges and housings required for a given flow rate and cartridge type, with fouling margin built in.
Inputs
Results
Effective max flow per cartridge
Q_cart_eff = Q_cart_max × (loading% / 100)
Number of cartridges
n_carts = ⌈Q_design / Q_cart_eff⌉ (ceiling)
Number of housings
n_housings = ⌈n_carts / per_housing⌉ (ceiling)
Flow per cartridge at design
Q_per_cart = Q_design / n_carts
% of rated capacity
%_rated = (Q_per_cart / Q_cart_max) × 100
Calculator 4 of 4
Ultrafiltration (UF) Membrane Sizing
Size hollow-fiber UF membrane modules for a target net permeate flow. Net flux and backpulse efficiency are accounted for automatically.
| Application | Typical Net Flux |
|---|---|
| High-quality groundwater | 25–35 GFD |
| Low-turbidity surface water | 15–25 GFD |
| High-turbidity / pre-RO | 10–18 GFD |
| Wastewater tertiary | 8–15 GFD |
Inputs
Results
Gross flux (instantaneous filtration flux)
Flux_gross = Net_flux / (BP_efficiency / 100)
Total permeate flow in GPD
Q_p_GPD = Q_p_GPM × 1440
Required membrane area
A_total = Q_p_GPD / Net_flux_GFD (ft²)
A_m² = A_ft² / 10.764
Number of modules
n_modules = ⌈A_total / A_per_module⌉ (ceiling)
Actual net flux
Flux_actual = Q_p_GPD / (n_modules × A_per_module) GFD
Backpulse flow
Q_bp = Q_p_GPM × ((100 / BP_efficiency) − 1) GPM
System footprint estimate
Footprint ≈ n_modules × 4 ft² (rough rule for 8" modules)
Unit conversions
GFD → LMH: multiply by 1.699 | ft² → m²: divide by 10.764