Unicel Replacement Filter Cartridge 75 sf Rainbow RTL-75 | C-4975
Unicel
SKU: C-4975
Unicel C-4975 – 75 sq ft Replacement Cartridge
Product Overview
The Unicel C-4975 is a high-quality replacement cartridge filter designed for spa and pool systems. With approximately 75 square feet of pleated polyester media, it offers excellent debris capture and flow performance for compatible filter tanks.
Key Features
- 75 sq ft of filtration area to handle heavier loads and extend cleaning intervals.
- Durable polyester media combined with a reinforced core and end caps for repeated use and rinsing.
- Precision dimensions: Outside diameter ~4-15/16", length ~20-1/8", and inner diameter ~2-1/8" (open both ends).
- Direct replacement for a variety of cartridge filter models from several manufacturers.
Technical Specifications
- Part Number: C-4975
- Square Feet: ~75 sq ft
- Outside Diameter: ~4-15/16” (~125.4 mm)
- Length: ~20-1/8” (~511 mm)
- Inner Diameter (both ends): ~2-1/8” (~54 mm), open end style
- Pleat Count: ~210 pleats
Applications & Compatibility
This cartridge is suitable for use in many spa and pool systems where the original cartridge specified a 4-15/16" diameter and 20-1/8” length with open ends. Its large filtration area and reliable construction make it a good choice for replacing worn cartridges in commercial or high-usage residential systems.
Installation Instructions
- Turn off the pump and relieve pressure from the filter system before opening the tank.
- Remove the old cartridge, clean the filter tank interior and inspect for signs of wear or damage.
- Insert the new C-4975 cartridge, ensuring it is correctly seated and the open ends are properly aligned with the filter tank ports.
- Reassemble the filter tank, restore power and pump operation, then monitor pressure and flow to confirm proper installation.
Troubleshooting & Tips
- High pressure on start-up: Verify that the cartridge pleats are fully expanded and not compressed or bent.
- Reduced flow: Check for debris build-up in pleats; rinse cartridge thoroughly or consider replacement if media is damaged.
- Leaks or bypass in tank: Ensure the cartridge only fits one orientation (open ends match tank ports) and that the tank lid or closure is sealed correctly.
Maintenance Tip
For best results, rinse the cartridge monthly (or more often in heavy use or high debris systems) and schedule replacement every 12-18 months or when the pleats show a permanent discoloration or damage. Keeping the cartridge clean and replacing at the appropriate interval helps maintain water clarity, system efficiency, and prolongs pump and heater life.
Questions about returns? View our return policy.
Hours Of Operation:
Monday - Friday: 7:00 am to 5:00 pm Phoenix Time
Saturday: 8:00 am to 2:00 pm
Sunday: Closed
- We do not ship on Saturday or Sunday.
- Orders totaling more than $300 will require signature confirmation upon delivery.
- We process and prepare orders for shipment within 1 business day. Please note that many other pool supply retailers require 3–5 days of handling time before shipping.
- Orders placed after 1:00 pm Phoenix Time may not be eligible for same-day shipment.
- Expedited shipping options are available at checkout.
Return Policy:
- Products that are received damaged will receive a refund in store credit.
- Most products are eligible for return within 30 days of receipt, except where noted below.
- To initiate a return, please complete an RMA form prior to sending your item back.
- Original shipping costs are non-refundable and will be deducted from the return credit.
- Items returned missing accessories or original packaging, or that are not in the same condition as received, may be subject to a restocking fee of up to 100% depending on the condition of the item upon return.
- Some returns will be charged an automatic 15% restocking fee.
- We are unable to issue refunds for items that have been damaged or rendered inoperable due to installer error.
- Please complete the return form to receive your RMA number and return shipping label.
- Chemical products are not eligible for return under any circumstances.
- The Pentair Colorsync 618031 is not eligible for return.
- Pool cleaners are not eligible for return.
- Opened seals and o-rings are not eligible for return.
- Capacitors are not eligible for return.
- Plastic popup tools are not eligible for return.
- Automation components and circuit boards are not eligible for return.
- If a light is returned due to a reported malfunction and is found to be fully operational upon testing, return shipping costs and a restocking fee will be deducted from the refund.
- Orders refused at the time of delivery will be subject to the original shipping costs being deducted from the refund.
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