vertical cylindrical pool filter cartridge with blue end caps and white pleated fabric wrapped label with cartoon character and product details
tall cylindrical pool filter cartridge with white pleated material and blue plastic top and bottom edges
cylindrical pool filter cartridge with white pleated material and blue plastic end cap labeled unicel and 4CH-21 on white background
cylindrical pool filter cartridge with pleated white filter material and bright blue plastic end cap with central hole

Unicel 4000 Series 19 sq. ft. Replacement Filter Cartridge | 4CH-21

Regular price$36.99
/
$9.99 flat shipping on orders under $100.
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SKU:
4CH-21
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About This Item

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
Top Cap
Bottom Cap: 1-1/2" male thread/MPT
Bottom Cap

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.)
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Unicel Filter Cartridges and DE Grids

About Unicel Filter Cartridges and DE Grids

The "Gold Standard" of Replacement Cartridges
For over 50 years, Unicel (Meissner Mfg.) has been the professional's choice for restoring pool water clarity. While generic "knock-off" filters often use cheap, fuzzy fabric that clogs quickly, Unicel uses genuine Reemay® Filtration Media. This patented synthetic fiber features a unique trilobal shape that traps significantly more dirt and oils without choking your pump's water flow. Based in California, Unicel doesn't just copy filter dimensions; they engineer them to strict Original Equipment Manufacturer (OEM) specifications. This ensures a "lock-tight" fit in your filter tank, preventing debris from bypassing the system and returning to your pool.

Why We Trust Unicel Filter Cartridges and DE Grids
Genuine Reemay® Media: Uses continuous trilobal fibers to capture microscopic debris without restricting water flow.

Precision "Exact Fit": Engineered to match your tank's original specifications for a 100% leak-free seal.

Made in the USA: Manufactured in California with heavy-duty urethane end caps that resist cracking under pressure.

Longer Lifespan: Sharp, rigid pleats resist collapsing during cleaning, meaning you buy fewer replacements over time.

More about Pool and Spa Filter Cartridges

Complete Your Pool Care Routine

Essential Pairing
Filter Cleaning Chemicals for All Types of Pool & Spa Filters

Using a specialized cleaner like FilterWash helps release deeply embedded oils and minerals that standard rinsing leaves behind.

Shop Filter Cleaning Chemicals for All Types of Pool & Spa Filters
Highly Recommended
Pool and Spa Plumbing Lubricants

Every time you open your filter tank, you must lubricate the O-ring to prevent dangerous leaks and ensure a watertight seal.

Shop Pool and Spa Plumbing Lubricants
Pro Tip: Don't Forget
Pool Test Kits and Water Analysis Tools

Balanced water pH prevents calcium scale from hardening your filter fabric and ruining your new cartridges.

Shop Pool Test Kits and Water Analysis Tools

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