Unicel C-7375 | 75 sq ft Caldera Spa Filter

By Unicel
SKU: C-7375
$73.99

Let's Ensure This Fits Your Model

Check out the Filter Guide to see if this filter fits your hot tub model.

If you have questions, call us at (208) 973-1384 or send us an email to hello@leisuretimeinc.com

If possible, please have your hot tub’s serial number ready when you contact our team.

Description

The Unicel C-7375 delivers 75 square feet of filtration across 216 pleats of Reemay® 2033 polyester media. Built to meet or exceed OEM specifications, it's the replacement cartridge for new-style Caldera® Spas, taking the place of Caldera parts 73531 and 1019301.

Filtration is the quiet backbone of clean spa water. Every soak leaves behind body oils, lotions, hair, and fine debris, and the cartridge is what removes all of it before it clouds the water, feeds bacteria, or coats your plumbing. When a filter is worn or clogged, the effects spread everywhere: dull water, higher chemical use, softer jets, and a pump and heater straining against restricted flow.

This is a substantial cartridge — 14-3/4 inches tall with 75 square feet of filtering surface — sized for the demands of a full-size Caldera spa. A semi-circular handle molded into the top makes lifting it out for cleaning effortless, while the 2-11/16 inch open bottom seats into the housing for a proper seal. Add Reemay's trilobal fibers, uniform pleat folds that keep flow strong and pressure loss low, and chemical-resistant end caps, and you get a cartridge built to perform through cleaning after cleaning. Made in the USA.

Pro Tip: This is the "new style" Caldera cartridge — verify yours before ordering. Caldera changed filter designs across model years, and this cartridge covers the newer configuration with a handle on top and a 2-11/16 inch open bottom. The fastest check is to pull your current filter and look at the ends: if it has a molded handle and an open bottom of that size, this is your replacement. If the numbers 73531 or 1019301 appear on it, you're in the right place.

Brand

UNICEL®

Key Features
  • 75 sq ft of filtration — full OEM-spec filtration area across 216 pleats
  • Direct Caldera replacement — takes the place of parts 73531 and 1019301
  • Semi-circular handle — makes removal and cleaning effortless
  • 2-11/16 in open bottom — the correct configuration for new-style Caldera housings
  • Reemay 2033 polyester media — balances dirt-holding capacity, cleanability, and chemical resistance
  • Made in the USA — built to meet or exceed OEM standards
How It Works

Water is drawn through the cartridge's pleated media as your spa circulates. Pleating creates the capacity: folding the fabric into 216 pleats packs 75 square feet of filtering surface into a cartridge 7 inches across and 14-3/4 inches tall. More surface means water passes through more slowly and thoroughly, capturing finer particles, and it means the filter holds far more debris before flow starts to drop off.

The media does the rest. Reemay fibers are trilobal — three-lobed in cross-section rather than round — which packs considerably more surface area into the same material, giving more places for dirt to be captured and a smooth surface that releases it readily when rinsed. Just as important is the fit: Unicel engineers its cartridges to the original manufacturer's exact dimensions, producing a tight seal in the filter housing. A loose cartridge lets water bypass the media entirely, sending debris straight back into your spa no matter how good the filter fabric is.

Pro Tip: A clean filter protects your equipment, not just your water. As the pleats load up with body oils, your pump has to work harder against the restriction, and reduced flow across the heater can trigger flow-related errors. Regular rinsing and periodic deep cleaning is the cheapest protection there is for the expensive parts of your spa.

Directions for Use

Installation

  1. Turn off power to the spa at the breaker before servicing the filter compartment.
  2. Open the filter lid and clear any debris from the compartment.
  3. Lift the old cartridge out by its handle, noting its orientation.
  4. Seat the new cartridge squarely in the filter well, fully seated so the open bottom engages the housing connection properly.
  5. If your spa uses more than one cartridge, replace them at the same time so they wear evenly and flow stays balanced.
  6. Close the lid, restore power, and run the circulation to confirm normal flow.

Routine Cleaning

  1. Every two to four weeks: lift the cartridge out by the handle and rinse gently with a garden hose, working between the pleats from top to bottom. A soft brush cleaning tool helps.
  2. Periodically: soak or treat the cartridge with a dedicated filter cleaner to dissolve the body oils and buildup a rinse can't remove, then rinse it off.
  3. Let it dry fully before returning it to service whenever possible.

When to Replace

  • The cycle between cleanings gets noticeably shorter
  • Low water flow or high differential pressure
  • The media has a tear
  • The center core collapses

Cartridge life depends on routine maintenance and your spa's water chemistry.

Pro Tip: Keep a spare cartridge in rotation. A proper chemical soak takes hours, and a cartridge this size cleans best when it can dry completely afterward — awkward when your spa needs it back right away. With a second cartridge you can drop in a clean one immediately and service the other on your own schedule, so your spa never runs on a dirty filter and both last longer.

Specifications
  • Brand: Unicel (Meissner Mfg. Co., Inc.)
  • Part Number: C-7375
  • Series: Unicel 7000 Series
  • Product Type: Replacement spa filter cartridge
  • Filtration Area: 75 sq ft
  • Pleat Count: 216
  • Media: Reemay 2033 spunbonded polyester, 3 oz basis weight
  • Outer Diameter: 7 in
  • Length: 14-3/4 in
  • Top: Semi-circular handle
  • Bottom: Open, 2-11/16 in inner diameter
  • End Caps: Durable plastic, chemical-resistant, exact OEM fit
  • Fits: Caldera Spas (Watkins Mfg.) — new style
  • Replaces OEM: Caldera Spas 73531, 1019301
  • Cross-References: Pleatco PCD75N, Filbur FC-3964, Baleen AK-60032, APCC7500, 17543
  • Cleaning: Rinse gently with a garden hose every two to four weeks; deep clean periodically with filter cleaner. Do not pressure wash.
  • Origin: Made in the USA
  • Shipping: Standard ground; not classified as a hazardous material

  • Outer Diameter: 7"
  • Length: 14-3/4"
  • Top End Cap: semi-circular handle
  • Bottom End Cap: 2-11/16" / open
  • Pleat Count: 216
  • Media: 3 oz.
  • Filtration Square Footage: 75 sq. ft
Compatibility

The C-7375 is built for new-style Caldera® Spas (Watkins Mfg.) systems. It serves as a direct replacement for these OEM cartridges:

  • Caldera Spas: 73531, 1019301

It's also cross-referenced as Pleatco PCD75N, Filbur FC-3964, Baleen AK-60032, APCC7500, and 17543.

Before ordering, verify the end configuration — semi-circular handle on top, 2-11/16 inch open bottom — along with the 7 inch diameter and 14-3/4 inch length, since Caldera has used more than one cartridge design across its model years. Also confirm how many cartridges your spa takes. The surest method is to pull your current cartridge and read the part number printed on it. For upkeep, pair it with a dedicated filter cleaner for periodic deep cleaning.

  • Utopia Geneva GEB 2000-2004
  • Utopia Hawaiian HAB 2001-2002
  • Utopia Niagara HIB 2000-2004
  • Utopia Provence 2018-2021
  • Utopia Tahitian 2000-2004
  • Paradise Geneva GEA 2002-2004
  • Paradise Hawaiian HAA 2000-2010
  • Paradise Makena MAA 2013-2023, 2025-Current
  • Paradise Moorea 2006-2010
  • Paradise Niagara NIA 2000-2002
  • Paradise Reunion 2019-Current
  • Paradise Salina 2011-Current
  • Paradise Seychelles 2019-Current
  • Paradise Tahitian 2002-2005
  • Highland Cascade 2002-2003
  • Highland Olympia 2000-2009
  • Highland Palomar 2004-2005
  • Highland Teton 2001
  • Aquatic Melodies Aspire 2004
  • Aquatic Melodies Elation 2003-2008
  • C-Series C30 C30 2006-2009
  • C-Series C30S C30S 2006-2009
  • C-Series C45 C45 2006-2009
  • C-Series C45S C45S 2006-2009

This is a replacement for the Caldera Utopia 73531 Filter Cartridge

Most products purchased from our online shop within the last 30 days are eligible for return. Please review our return policy to see the list of items that cannot be returned.

Some major items that are non-returnable:

  • Gift cards
  • Electronics
  • Pumps / Motors
  • Hot Tubs
  • Closeouts
  • Fireplaces
  • Electric Fireplaces
  • Massage Chairs
  • See return policy below for full list of non-returnables.

UNICEL® Brand FAQs

Who makes Unicel filters?

Unicel filters are made byMeissner Mfg. Co., Inc., a family business that began as a small contract sewing operation in thelate 1950sand moved into pool filtration through the 1970s. By the end of that decade the company was producing cartridge filters for the industry'soriginal equipment manufacturers, and in1985it introduced the Unicel brand as aftermarket replacements. It's still owned and operated by the Meissner family today.

Are Unicel filters as good as the original manufacturer's filter?

Unicel builds its cartridges tomeet or exceed original equipment specifications— and that's a meaningful distinction here, because the company produced cartridges for the industry's OEMs before it ever launched its own brand. Unicel cartridges usedurable, chemical-resistant end capswith an exact fit,high-capacity media,uniform pleatsfor optimal flow, and asolid corethat resists collapsing under pressure.

Where are Unicel filters made?

Unicel filters are manufactured inCalifornia, with components sourcedexclusively in the United States. The line comprisesnearly 500 products, covering replacement cartridges, D.E. grids, filter discs, and related parts.

How do I find the right Unicel filter for my spa?

Unicel cartridges areinterchangeable with all major filter brands, and each one cross-references to a list of original equipment part numbers. The most reliable method is topull your current cartridge and read the part number printed on it, then match it to the Unicel cross-reference. If the number has worn off,measure your old cartridge— diameter, length, and the size and style of the openings at each end — and match those instead. Also confirmhow many cartridgesyour spa uses.

How long does a Unicel filter last?

Cartridge life depends on how heavily the spa is used, yourwater chemistry, and how consistently you clean the filter. Many Unicel cartridges useReemay® polyester media, whosetrilobal fibersprovide considerably more surface area than standard rounded fibers — which increases dirt-holding capacity and extends the time between cleanings. With regular rinsing and periodic deep cleaning, a well-maintained cartridge commonly serves a year or more.

When should I replace my filter instead of cleaning it?

Replace the cartridge when thecycle between cleanings becomes noticeably shorter, when you seelow water flowor high differential pressure, when the media has atear, or if thecenter core collapses. Pleats that stay permanently flattened or discolored after a proper cleaning are another sign the cartridge has reached the end of its service life.

About UNICEL®

Unicel is the nation's leading manufacturer of replacement filter cartridges for pools and spas — and the story behind it is a genuinely American one. In the late 1950s, Richard T. Meissner started a small part-time contract sewing operation. Through the 1970s, Meissner Mfg. Co., Inc. moved into swimming pool filter bags, then D.E. grid element covering, and by the end of that decade the company was producing cartridge filters for the industry's original equipment manufacturers.

That's the detail that matters most: Unicel was building the filters that went into new spas long before it sold a replacement. In 1985, the company introduced the UNICEL brand so dealers and technicians could source elements built to O.E.M. specifications from a single place — even for equipment brands they didn't carry. Today the line spans nearly 500 products, all manufactured in California with components sourced exclusively in the USA.

By staying focused on one thing — filtration — Unicel has built deep expertise in a critical corner of the industry, from media development to cartridge design. Every cartridge is built with chemical-resistant end caps for an exact fit, high-capacity filter media, uniform pleats for optimal flow, and a solid core that holds its shape under pressure. Meissner Mfg. Co., Inc. remains owned and operated by the Meissner family, still recognized for quality and service. American-made products, world-class service.