1 1

Fleck 28413-US - Piston - lower with No Bypass (NBP) 60104

Fleck 28413-US - Piston - lower with No Bypass (NBP) 60104

0401185607

Low stock

£149.00 inc. VAT
£124.17 ex. VAT
£149.00 inc. VAT
£124.17 ex. VAT
Shipping calculated at checkout.
Shipping is calculated at checkout
Please ensure you order the correct Water Softener/Filter/Valve parts and Media as returns are not available for these products, as per our Terms and conditions and refund/return policy.
If you would like delivery to Scottish Highlands or UK Offshore Areas.Please contact us for Accurate Shipping charges. Call Now
Order Before 2pm For Same Day Processing

Product Description

WrekinWater stocks the Fleck 28413-US Lower Piston, the no-bypass (NBP) version of the lower piston assembly (part 60104), a genuine Pentair Fleck replacement for softener valves fitted without an integrated bypass, for when hardness starts breaking through or water begins running to drain outside the regeneration cycle.

Technical specifications

Part Number 28413-US (60104)
Position Lower piston
Bypass Configuration No Bypass (NBP)
Assembly Type Complete piston with seals
Material Engineered polymer piston with NBR seals
Brand Pentair Fleck

Symptoms that mean you need this part

  • Water continuously flowing to drain even when the softener is not regenerating
  • Softened water quality dropping between service and regeneration cycles
  • Grooves, flat spots or hardened rubber visible when the old lower piston is inspected
  • Dripping or weeping around the lower valve body outside the normal regen schedule

Why it fails / why it matters

On an NBP valve, the lower piston does the same repeated back-and-forth job as its WBP counterpart but without a bypass assembly to fall back on if it fails, so any wear in the piston's seal surface shows up directly as leaking to drain or hardness slipping through. Thousands of cycles gradually wear a groove into the seal contact area, and once that happens the piston can no longer seal cleanly between valve positions.

Why buy this from WrekinWater

WrekinWater has supplied genuine Fleck spares to more than 50,000 customers over 15 years from our base in Bettisfield, Shropshire, and stocks Pentair Fleck alongside Autotrol, Clack, Kinetico and other major brands, so this NBP piston is matched to the correct valve configuration. We're UK Company No. 11000488, rated "Excellent" on Trustpilot.

How to fit it

  1. Isolate the softener at the inlet and relieve system pressure before starting
  2. Remove the valve cover and drive assembly to access the lower piston
  3. Withdraw the old piston and check the seal surface for grooves, flat spots or hardened rubber
  4. Clean the valve bore to remove any scale or debris before fitting the replacement
  5. Lubricate the new NBP piston assembly with a silicone-based lubricant approved for potable water and fit it in place
  6. Reassemble the drive assembly, restore the water supply, and run a manual regeneration to check for leaks and correct operation

Frequently asked questions

Check whether your existing softener has a separate bypass valve fitted at the inlet/outlet. If it does, the valve itself is likely NBP and relies on that external bypass; if the valve body has bypass built in, you need the WBP piston instead.

Yes, this is a genuine Fleck 28413-US assembly, also listed under part number 60104, supplied as a complete piston unit with seals.

Yes, this is a standard DIY-level part swap for anyone comfortable opening the valve body — no specialist tools are required.
Fleck 28413-US - Piston - lower with No Bypass (NBP) 60104

Fleck 28413-US - Piston - lower with No Bypass (NBP) 60104

£149.00 inc. VAT
£124.17 ex. VAT
£149.00 inc. VAT
£124.17 ex. VAT