Sump Backflow Calculator

Wet Pets Power Outage Backflow Calculator

Estimate whether your sump has enough empty space to catch display tank drain-down during a power outage.

All dimensions should be entered in inches unless otherwise noted. Volumes are displayed in U.S. gallons.

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Display Tank Drain-Down
Measure inside length for best accuracy.
Front-to-back inside width.
Estimated drop before siphon breaks or overflow stops draining.
Additional water from return lines, overflow boxes, UV units, reactors, etc.
Sump Freeboard
Inside sump length.
Inside sump width.
Distance from normal operating water level to the maximum safe fill level.
Recommended: 10–25% extra capacity.
Total Backflow Volume (gallons) 0.0 gallons
Sump Freeboard Capacity (gallons) 0.0 gallons
Required Capacity w/ Safety Margin (gallons) 0.0 gallons
Remaining Capacity Margin (gallons) 0.0 gallons
SAFE
Display Drain-Down Only (gallons) 0.0 gallons
Estimated Sump Water Rise (inches) 0.00 inches
Recommended Empty Height Required (inches) 0.00 inches

This calculator is an estimate. Always physically test a system by turning off the return pump while watching the sump water level. Keep return nozzles near the surface, use siphon breaks where appropriate, and do not rely only on check valves to prevent flooding.

Setting up a sump or reef system? Bring your tank and sump dimensions to Wet Pets Aquatics and we can help check your outage safety margin.