Flojet 20041-000 Piston Kit, Nylon/Nylon
The Flojet 20041-000 is the genuine nylon piston kit for Flojet diaphragm pumps. The pistons are the rigid components clamped either side of the diaphragm that transfer the cam’s motion into it — they are what actually pushes and pulls the flexible membrane through its stroke.
Their job is more subtle than simply pushing. The pistons hold the centre of the diaphragm rigid while allowing the surrounding area to flex, which controls the shape the diaphragm takes on each stroke and therefore how much volume it displaces. They also clamp the diaphragm centre, and that clamp is what stops the membrane tearing away from its mounting under the repeated load. Pistons that have worn, cracked or lost their grip let the diaphragm flex where it should not, which is a reliable way to destroy an otherwise healthy diaphragm.
Nylon is specified because it is stiff, dimensionally stable, self-lubricating against adjacent plastic surfaces and immune to corrosion — all useful in a permanently damp assembly. Replace the pistons when they are cracked, visibly worn where they contact the diaphragm, or when the clamping faces are no longer flat. Fit them with a new diaphragm rather than onto a used one, and observe the orientation given in the instructions — pistons fitted the wrong way round change the stroke geometry.
Key Features
- Genuine Flojet (Xylem) service part — correct dimensions and clamping faces
- Nylon construction — stiff, dimensionally stable and corrosion-proof
- Holds the diaphragm centre rigid while letting the surrounding area flex correctly
- Correct clamping keeps the diaphragm from tearing away under repeated load
- Supplied as a kit so both pistons are renewed together
Applications
- Flojet diaphragm pump rebuild and overhaul
- Fitted alongside a diaphragm replacement
- Repairing a pump where cracked pistons have damaged the diaphragm
- Restoring correct stroke geometry and displacement
- Marine, RV, dockside and mobile water systems
Specifications
- Brand: Flojet (Xylem)
- Manufacturer Part Number: 20041-000
- Part Type: Piston kit
- Material: Nylon
- Function: Transfers cam motion into the diaphragm and clamps its centre
- Condition: New
Frequently Asked Questions
Q: Do the pistons need replacing every time the diaphragm is changed?
Not necessarily, but inspect them closely. Any crack, wear ridge or unevenness on a clamping face will shorten the life of the new diaphragm considerably.
Q: What does a cracked piston do to the pump?
It lets the diaphragm centre move and flex where it should be held rigid, which fatigues the membrane at exactly the point it is least able to take it.
Q: Does piston orientation matter?
Yes. The instructions specify which way they face, and reversing them changes the stroke geometry and how the diaphragm is clamped.
Q: Why nylon rather than metal?
Nylon will not corrode in a permanently wet assembly, is self-lubricating against adjacent plastic parts, and is light enough that it adds no meaningful inertia to a fast-reciprocating mechanism.
Not sure this is the right part? Send us a Picture of the pump plate on your pump and the CLR Marine team will confirm the correct part before you order.
CLRMarine
