Back washing Valve commonly used on Carbon, Birm, and Calcite tanks.
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< Tank Diameter - How To Measure and Why >NOTE: 230 Volt / 50 Hz version does not ship until 2 weeks after paid order is received.
"Carbon Filter" assumes the media tank is using only Carbon with Gravel under bedding.
"Filter Backwash" assumes the media tank is using something "Heavier" than Carbon, such as BIRM, Calcite, Green Sand, Pyrolox, and Gravel under bedding.
And that is the reason for the higher Backwash Flow Rating per Tank Diameter.