The Unicel 4CH-21 is a 4000 Series 19 sq. ft. replacement filter cartridge engineered for top-load spa and hot tub filtration systems with a 1-1/2″ MPT threaded suction connection. With 158 pleats of 3 oz. Reemay 2033 polyester media, this cartridge delivers consistent particle capture and reliable water clarity in compact spa filter housings. The molded cone handle on top simplifies removal at service time, while the 1-1/2″ male pipe thread bottom threads directly into the spa’s suction fitting no separate adapter required on most compatible systems.
Specifications
| Filter Area | 19 sq. ft. |
| Length | 8″ |
| Outer Diameter | 4 5/8″ |
| Top Inner Diameter | N/A |
| Bottom Inner Diameter | N/A |
| Material | 3 oz. Reemay 2033 |
| Pleat Count | 158 |
| Top Cap: molded cone handle | Bottom Cap: 1-1/2″ male thread/MPT |
Fits into:
| OEM Brand | Product Name | Part Number | Notes |
| Alcove | – | – | – |
| Atera Spas (Four Seasons Home Resort Products) | – | – | – |
| Dream Maker Spas | – | – | Remove pad adaptor (if present) from skimmer before threading MPT directly into suction fitting; 2000 to present w/LED lights |
| Pageant Spas | – | – | – |
| Saratoga Spas | – | 20245-238 | – |
| Unicel | 19 sq. ft. top load | – | Designed for systems using a 1-1/2″ MPT threaded connection. Also replaces open-bottom filters (approx. 1.9″ inner diameter) previously used with a separate removable threaded adapter in the spa’s suction fitting. |
| Vita Spas | – | PVT 25N | Remove pad adapter from the skimmer before threading Unicel MPT directly into the suction fitting. |
(This is not an exhaustive list.)
