Flojet 20028-003 Valve Chamber Sub-Assembly, Santoprene
The Flojet 20028-003 is the genuine valve chamber sub-assembly in Santoprene, carried under the factory designation "Valve Chamber S/A Sto 2BP". The valve chamber is the upper half of a diaphragm pump — the part containing the inlet and outlet check valves that turn the diaphragm’s back-and-forth motion into flow in one direction.
Those check valves are the most common cause of a diaphragm pump that has gone soft. Each is a flexible elastomer flap sealing against a machined seat, and the sealing gap is measured in thousandths of an inch. Over time the elastomer hardens, takes a set, or is cut by a piece of grit that got past the strainer, and once it no longer seats the pump pushes water backwards on part of every stroke. The symptoms are unmistakable once you know them: reduced flow, a pump that will not reach its cut-out pressure, cycling with no tap open, or one that will not prime.
Santoprene is a thermoplastic elastomer chosen for exactly this duty. It keeps its flexibility across a wide temperature range, resists the compression set that turns an old valve flap into a stiff disc, and stands up well to water, detergents and dilute chemistries. Supplied as a sub-assembly, the chamber arrives with its valves already fitted correctly — valve orientation is easy to get wrong, and a valve fitted backwards produces a pump that runs perfectly and moves nothing.
Key Features
- Genuine Flojet (Xylem) service part — supplied as a complete sub-assembly
- Santoprene valves for flexibility, set resistance and broad chemical tolerance
- Valves arrive correctly seated and oriented — no risk of fitting one backwards
- Restores flow, pressure and priming lost to worn or cut check valves
- Factory designation: Valve Chamber S/A Sto 2BP
Applications
- Flojet diaphragm pump rebuild and overhaul
- Restoring a pump that has lost flow or will not reach cut-out pressure
- Curing cycling with no outlet open
- Repairing valve damage after grit has passed the strainer
- Marine, RV, dockside and mobile water systems
Specifications
- Brand: Flojet (Xylem)
- Manufacturer Part Number: 20028-003
- Part Type: Valve chamber sub-assembly
- Valve Material: Santoprene
- Factory Designation: Valve Chamber S/A Sto 2BP
- Condition: New
Frequently Asked Questions
Q: How do I know it is the valves rather than the diaphragm?
A failed diaphragm usually stops the pump priming at all and may leak into the motor area. Worn valves typically leave the pump running normally but delivering less and struggling to reach cut-out.
Q: Why buy the chamber rather than loose valves?
Because orientation and seating are easy to get wrong and impossible to check once assembled. A sub-assembly removes both risks and takes far less time to fit.
Q: What is Santoprene and why is it used here?
It is a thermoplastic elastomer that combines rubber-like flexibility with good resistance to taking a permanent set, which is precisely what a valve flap cycling thousands of times a day needs.
Q: Should I fit a strainer at the same time?
If the old valves show cuts or embedded grit, yes. Renewing the valves without fixing what damaged them simply restarts the clock.
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.
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