Fleck 26494-00 - Piston with No Bypass (NBP) 2850

The Fleck 26494-00 is a genuine no-bypass (NBP) piston assembly built for Fleck 2850 series control valves, the component that physically directs water flow through service and regeneration cycles inside your water softener or filter head. WrekinWater stocks this exact part for customers whose 2850 valve is sticking, leaking, or failing to regenerate cleanly, and who need a like-for-like replacement rather than a generic substitute that won't seal properly in an NBP configuration.

Technical specifications

Symptoms that mean you need this part

• Softener runs its regeneration cycle but water still feels hard afterwards
• Water leaking from the valve body or drain line during or between cycles
• A grinding, sticking or knocking noise as the valve indexes through its cycle
• The old piston shows visible scoring, pitting or flattened seal rings when removed

Why it fails / why it matters

The piston sits at the heart of the valve, sliding back and forth thousands of times a year to route water between the resin bed, drain and brine tank. Hard water carries fine grit, iron particles and mineral deposits that gradually abrade the piston surface and its rubber seals, while resin fines can score the bore it travels through. Once the seals lose their shape or the piston surface pits, water starts bypassing the seal stack internally, so the valve either leaks or stops directing water correctly during regeneration, even though the electronics and timer are working perfectly.

Why buy this from WrekinWater

WrekinWater has served more than 50,000 customers over 15 years from our base in Bettisfield, Shropshire, and we stock genuine Pentair Fleck parts alongside Autotrol, Clack, Kinetico and other major brands, so you get the correct fit first time rather than a compatible-but-not-quite part. As a family run company rated "Excellent" on Trustpilot, we're on hand if you need help confirming your valve type before you order.

How to fit it

1. Turn off the water supply to the softener and put the valve into bypass if fitted.
2. Relieve system pressure by opening a downstream tap or the softener's pressure relief button.
3. Remove the valve body screws or retaining clip to access the piston assembly.
4. Withdraw the old piston, comparing the seal and spacer stack against the new 26494-00 to confirm an exact match.
5. Fit the new piston into the valve body, ensuring seals are seated and not twisted, then reassemble the housing.
6. Restore the water supply, take the valve out of bypass and run a manual regeneration to check for leaks and correct cycling.