Piston Assy, 9500, Lower EPDM

This Fleck Piston Assembly is the 9500 Lower, EPDM version (FL60109-02), the lower-section piston for the high-capacity Fleck 9500 control valve fitted with EPDM-compound seals. The 9500 relies on coordinated upper and lower pistons to route flow through service and its multi-stage regeneration cycle, and this is the EPDM-sealed lower component built for broad compatibility.

About the EPDM configuration

• Lower piston assembly for the Fleck 9500 valve
• EPDM seal compound for broad chemical and temperature compatibility
• Routes flow through the lower section of the cycle
• Genuine Pentair Fleck replacement part, valve model 9500
• Core wear component for periodic valve service
• Works in coordination with the upper piston for proper cycling

EPDM is a versatile sealing elastomer known for good resistance to heat, ozone, weathering, and a wide range of water chemistries, which can make it a preferred choice in certain applications and water conditions where other compounds would degrade. Matching the correct seal compound to your system is important: using the elastomer suited to your water and temperature ensures long-lasting, leak-free performance and avoids premature seal breakdown.

As the lower piston and its EPDM seals wear over time, the valve may develop internal bypass leakage, weak regeneration, or untreated water passing to the service line. On the twin-piston 9500, the lower section works in concert with the upper, so wear here affects the coordination of the whole cycle, not just a single position. These symptoms usually appear gradually, with softness slowly declining or salt consumption creeping upward, so periodic inspection helps catch wear before it becomes a noticeable problem.

When replacing this piston, install a fresh, matching seal and spacer kit at the same time so the new piston seats against new seals rather than old, grooved ones, and apply a light film of silicone lubricant to ease assembly. Confirm the upper and lower pistons are correctly timed with their cams during reassembly. Always place the valve in bypass, relieve pressure, and disconnect power before opening the control head for service. Choosing the EPDM-sealed lower piston where your water chemistry or temperature calls for it, and renewing the seals on schedule, keeps the 9500 cycling cleanly and protects the soft-water supply throughout the building.