The Fleck 18303 AS568-336 top of tank o-ring creates a leak-proof seal between your Fleck control valve and the tank opening. This precision-molded rubber seal is engineered to handle the pressure and chemical exposure of residential and commercial water softening systems.
SPECIFICATIONS
Technical Details
| Manufacturer | Fleck |
| Part Number | 18303 |
| O-Ring Standard | AS568-336 |
| Application | Top of tank seal |
| Material | Buna-N rubber |
| Component Type | Control valve seal |
| Suitable For | Water softener systems |
| Typical Lifespan | 5-7 years under normal conditions |
INSTALLATION & USE
Replacement Procedure
- Depressurize the system and disconnect the control valve from power, then remove the valve from the tank neck
- Clean the tank opening rim thoroughly and inspect for any cracks or damage that could compromise the new seal
- Position the new Fleck 18303 o-ring evenly in the groove at the top of the tank neck, ensuring no twists or folds
- Reinstall the control valve and hand-tighten according to manufacturer torque specifications to avoid over-compression
COMPATIBILITY
Valve Compatibility
This AS568-336 specification o-ring fits Fleck 5600, 5600SXT, 5810, 7000, and 9000 series control valves when mounted on standard tank neck openings. It is compatible with both downflow and upflow valve configurations used in water softening and filtration applications. Verify your tank neck diameter matches the 336 o-ring size before ordering.
🔧 Pro Tip: Lightly lubricate the o-ring with food-grade silicone grease before installation to extend seal life and make future removal easier. Avoid petroleum-based lubricants that can degrade the rubber over time.
