Differential pressure across a filter can be monitored by comparing gauges at its inlet and outlet while the system is operating. This calculator performs that gauge arithmetic only.
Water Purifying Filter Interactive Calculator
Enter simultaneous inlet and outlet gauge pressures plus a device-specific differential-pressure reference. Outputs are arithmetic comparisons—not a purity measurement, cartridge rating, service instruction or universal change-out rule.
Equation Used
- Inlet and outlet values are simultaneous gauge-pressure readings at the stated locations.
- Signed differential is inlet minus outlet.
- The positive-loss branch clamps only for threshold comparison; the signed result remains visible.
- The entered threshold is device-specific user input, not a default recommendation.
- Flow, clean-element baseline, fluid properties, gauge uncertainty, elevation, piping losses, media loading, contaminant removal, water quality, housing rating and service safety are omitted.
Two-Gauge Differential-Pressure Check
A 3M operating guide explains that filter differential pressure can be monitored as the difference between inlet and outlet gauge readings while running. Pentair product documentation shows that actual change-out differentials vary by product and process limits.
What This Calculator Represents
The tool subtracts two entered gauge readings, forms one ratio, and compares only a positive pressure-loss magnitude with an entered reference.
Signed Gauge-Difference Calculation
dP+=max(0,dP)
retained ratio=100Pout/Pin
reference use=100dP+/L
remaining reference=L−dP+
Worked Gauge Example
For 40 psi inlet, 35 psi outlet and an entered 15 psi reference, signed difference is 5 psi, outlet/inlet ratio is 87.5%, reference use is 33.3% and remaining entered reference is 10 psi.
Model Boundary and Safety
- Calculated: gauge difference, ratio and comparison with entered reference.
- Illustrated: generic inlet gauge, filter housing/media and outlet gauge.
- Not calculated: contaminant removal, water purity, flow-dependent baseline, rating, service interval or safe depressurization.
Use the exact system manual and fully isolate/depressurize equipment before service.
Frequently Asked Questions
Is the entered reference a universal replacement limit?
No.
Does pressure difference measure water purity?
No.
What does a negative result mean?
The entered outlet reading exceeds the inlet reading; check locations, timing and instruments.
Are flow and clean-filter baseline included?
No.
Does this rate the housing?
No.
Can it authorize filter service?
No.
References
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