Pentair Autofill, Gray | T40BG Natural Chemistry The part number 400-4000 describes

The part number 400-4000 describes a Union Fitting that connects two 1-1/2 in socket ends

This gasket is typically replaced during blower service or when air leaks are detected

Listed size is 2 inch for proper replacement matching

Households with young children or curious pets who want an extra safety layer when the pool is not in use

Pentair Autofill, Gray | T40BG Natural Chemistry The part number 400-4000 describesWhat This Part Is Used For The Pentair T40BG Autofill Gray maintains proper pool water level automatically. It compensates for evaporation through a mechanical float system. Why This Part Matters Consistent water level prevents suction issues and equipment strain. An autofill reduces manual filling and stabilizes operation. It supports reliable skimmer and pump performance. Key Features and Specifications Pentair manufacturer part number: T40BG