Pool, Spa & Water Treatment Chemistry worked example
Filter Loading Rate with system flow through filter of 160 gpm: a worked example
What does the result look like when system flow through filter reaches 160 gpm? The full calculation is worked below with real intermediate numbers. Use it to check cartridge, sand, DE, or commercial filter sizing against design limits.
The inputs for this scenario
- System flow through filter: 160 gpm (raised for this scenario; the documented default is 65)
- Effective filter area: 300 ft2 (unchanged)
- Available filter area factor: 1 x (unchanged)
Working through the calculation
- Applying the documented formula (Filter loading rate = system flow / effective filter area / available area factor) to the inputs above produces each figure below.
- At this operating point the engine returns 0.53 gpm / ft2 for ratio, the number this scenario is built around.
- At this operating point the engine returns 0.53 value for raw ratio.
- At this operating point the engine returns 1 x for available area factor.
- At this operating point the engine returns 300 value for effective filter area.
How this compares with the baseline
- Against the tool's baseline example, where system flow through filter sits at 65 gpm and the headline result is 0.22 gpm / ft2, this scenario comes in 146% above the baseline at 0.53 gpm / ft2.
- A figure at this level is achievable when system flow through filter is genuinely sustained, not just peaked for a shift. Manufacturer-rated maximum loading rates vary widely by media type, so the computed number is only meaningful when compared against the specific filter's rating.
Results at a glance
- Ratio: 0.53 gpm / ft2 (headline result)
- Raw ratio: 0.53 value
- Available area factor: 1 x
- Effective filter area: 300 value
Run it with your numbers
- Every input above is editable in the live Filter Loading Rate calculator, which recalculates instantly and can be shared with the inputs intact.
Last reviewed 2026-05-12.