RDC 25 - Replacement Cartridge Filter - 340mm x 126mm

Premium Quality. Trusted Brands. No Gimmicks. 

Heater & Spa Parts only supplies premium-grade cartridge filters. Unless otherwise stated, our filters are Magnum® or Darlly® branded, made using USA-made Reemay®, Darlly®, Pleatco® filter media or equivalent. These two companies are among the biggest OEM suppliers to major spa and pool manufacturers, including Astralpool and many others.

Because we buy in container-load volumes, we can offer premium filters at sharper pricing and pass that value on to you.

Our filters are trusted across the industry, including by brands such as Astralpool, Balboa, Davey, Emaux, Halo Spas, Hurlcon, Madimack, Oasis Spas, Sapphire Spas, Spa World, Vortex®, SpaNet, Waterco, Zodiac, and more.

FYI, Most major manufacturers do not make cartridge elements themselves. They are supplied by OEM specialists like Magnum and Darlly, using Reemay or Darlly material, which are the same brands we supply.

These are not the cheap, unknown generics commonly sold on eBay, Wish, Temu, Amazon, and others. They are the same type of filters used by top manufacturers. 

NSF® certified materials

All our filters are made from NSF® certified materials, meeting international standards for safety, strength, and filtration performance. Brands like Darlly®, Magnum®, Pleatco®, and Reemay® are globally recognised for consistent quality.

Why we mostly use Darlly® and Magnum®

Darlly® and Magnum® filters (with Reemay® or equivalent media) are chosen for real-world reliability:

• Stronger, continuous fibres for minimal shedding
• Greater durability compared to low-grade alternatives
• Longer service life and fewer replacements
• Cleaner, healthier water

Low-quality filters can shed fibres that clog or damage equipment. Ours are engineered to reduce shedding and keep your system running clean and efficient.

Filter cleaning guide

Clean your filter when:

• Spas: water flow or jet pressure drops
• Pools: filter pressure is about 35-45 kPa above normal

How to clean:

1. Remove the cartridge as per your manufacturer’s instructions.
2. Soak in a proper filter cleaning solution (for example Zodiac Filter Soak or Filter Klenz).
3. Rinse thoroughly with a garden hose. A pleat-cleaning nozzle helps.
4. Reinstall carefully and check seals are seated correctly.

Maximise filter life:

• Maintain balanced water chemistry.
• Clean regularly based on usage.
• Do not scrub with hard brushes or use high-pressure hoses.
• Avoid flocculants and avoid overusing clarifiers.
• Rotate multiple cartridges where possible to extend lifespan.

When to replace your filter

We recommend replacing cartridge filters every 12 to 24 months, depending on usage and conditions. Keeping a spare on hand allows easy rotation and uninterrupted filtration.

Warranty information

All standard filters are covered by a 12-month replacement warranty (excluding disposable and inflatable-spa types). This covers defects in materials or workmanship, not damage caused by improper use or poor water chemistry. See examples and warranty terms on our warranty page.

Summary: why choose our filters

• NSF® certified materials for proven safety and performance
• Trusted by major brands across the industry
• Mostly Magnum® or Darlly® branded filters, using Reemay® media or equivalent
• No gimmicks, just reliable, proven filtration
• Premium quality at sharp pricing through container-volume purchasing

Your spa or pool deserves more than a “just good enough” filter. Choose proven quality, backed by trusted names and genuine product knowledge.