Hayward Locking Knob for Star-Clear Plus C900/C1200 — Hand-Tight Replacement Restores Seal

The Hayward Locking Knob is a direct replacement knob designed to securely fasten Star-Clear Plus cartridge filters (C900, C1200 and compatible models) for reliable, leak-resistant operation.

When a pool filter’s locking assembly becomes worn, stripped or lost, swapping in a compatible replacement knob restores proper clamping force and helps keep the filter cartridge sealed. This replacement part is made to fit Hayward Star-Clear Plus cartridge filters — including models C900 and C1200 — and the separation tank variant, providing a straightforward repair option that avoids costly full-head replacements. The unit weighs approximately 4.3 pounds and installs without specialized tools.

How does this knob restore filter performance?

Replacing a damaged or missing knob brings back the correct tension on the filter lid, which helps maintain a proper seal and reduces the chance of leaks or air entering the system. The knob is shaped to provide positive engagement with the locking post so the lid stays firmly seated during pump operation.

• Exact fit for Star-Clear Plus locking post geometry
• Restores even clamping pressure around the lid
• Helps prevent bypass and air infiltration into the cartridge
• Quick hand-tight installation — no adhesives required

Will this knob work with my Hayward cartridge filter?

This knob is intended specifically for Hayward Star-Clear Plus cartridge filters, including models C900 and C1200, and the compatible separation tank (CX900G-compatible applications). Confirm your filter model number before ordering to ensure compatibility. If your filter uses a different locking system or brand, this knob may not fit.

• Compatible with C900 and C1200 Star-Clear Plus models
• Fits the separation tank configuration used with similar Hayward systems
• Not universal — check model stamping on the filter housing
• Images and part numbers help verify compatibility

How easy is installation and what tools do I need?

Installation is designed to be user-friendly. In most cases the knob threads onto the existing locking post and secures by hand; no specialized tools are necessary. If the existing post is damaged, minimal cleaning or replacement of the post may be required for a secure fit.

• Hand-tighten knob for normal use
• No glue or sealant required for standard replacement
• May require light cleaning of threads prior to installation
• Refer to your filter manual for torque guidance if available

What should I expect for durability and maintenance?

The part is intended as a durable service replacement for routine pool maintenance. While not a wear item like a cartridge, it can deteriorate over many seasons from UV exposure, chemical contact or repeated over-tightening. Inspect the knob and locking post periodically and replace if you notice cracking, excessive play, or stripped threads.

• Durable under normal pool chemical conditions
• Resistant to routine wear but susceptible to UV aging over years
• Replace if threads are worn or knob cracks
• Light maintenance: rinse and inspect during seasonal cartridge checks

Who is this for? Pool owners, maintenance technicians and DIY-minded consumers who have a Hayward Star-Clear Plus cartridge filter (C900, C1200 or the compatible separation tank configuration) and need a reliable replacement for a worn or missing locking knob. It’s especially useful if you want a simple, low-cost repair that restores proper lid sealing without replacing the entire filter head.