Unicel 4CH-50 Replacement Spa Filter Cartridge – 50 Sq Ft (4″ OD x 14″ Length, 1-1/2″ MPT Threaded Bottom)
The Unicel 4CH-50 is a high-capacity 50 sq ft pleated spa filter cartridge designed for select hot tubs and spa filter canisters that use a threaded screw-in bottom connection. With its compact 4″ diameter body and taller pleat pack, it provides strong debris capture and longer run time between cleanings compared to smaller cartridges.
Key Features
- 50 sq ft filtration area for clearer water and steady circulation
- Bottom: 1-1/2″ male pipe thread (MPT) screw-in connection
- Top: open end for compatible standpipe/canister designs
- Durable pleated media and rigid core built for repeated cleaning cycles
- Ideal replacement when pleats are torn, flattened, or the cartridge stays restrictive after cleaning
Specifications
- Part Number: 4CH-50
- Filtration Area: 50 sq ft
- Outside Diameter: 4″
- Length: 14″
- Top End Cap: Open
- Top Inside Diameter: 2″ (open)
- Bottom End Cap: 1-1/2″ MPT thread
- Pleat Count: 220
- Media: 3 oz pleated media
Replaces / Cross References
- Pleatco: PWW50P3
- Filbur: FC-0172
- Darlly: 40505
- Baleen: AK-4003
- Other common references: 40025, 210-0100, 8CH-950 (verify by dimensions and thread style)
Compatibility Notes
- This cartridge uses a threaded bottom (1-1/2″ MPT). If your current filter has a different thread size (or a slip/non-threaded bottom), you need a different cartridge.
- Always confirm fit by matching the 4″ OD, 14″ length, and 1-1/2″ threaded bottom.
When to Replace
- Flow is weak or the spa struggles to maintain circulation even after cleaning
- Pleats are torn, frayed, flattened, or separating from the end caps
- The cartridge quickly plugs up again after rinsing
- End caps or the threaded connection are cracked/warped and won’t seal properly
Related Products
- Unicel 4CH-50 (Shop / Options)
- Spa Cartridge Filter Cleaner
- Cartridge Cleaning Wand
- Spa Water Test Strips
- Spa Fill / Hose Pre-Filters
- Silicone O-Ring Lubricant (Pool/Spa)
Maintenance Tips
- Rinse the cartridge regularly (often weekly with heavy use) to prevent restriction and keep flow strong.
- Deep clean every 3–6 weeks with a cartridge cleaner to remove oils; rinse thoroughly before reinstalling.
- If scale is present, degrease first, then treat for scale (never reverse the order), and rinse completely.
- Rotating between two cartridges (one in use, one drying after cleaning) can extend overall filter life and improve filtration performance.
