CPI - 3" Hub Adaptor with O Ring - 3.75" Hole Size - Part # 300

This 3" hub adaptor with O-ring is perfect for secure tank fittings, providing a reliable seal for a 3 3/4" hole size. Designed for durability and easy installation, it’s an essential part for your RV plumbing needs.
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The CPI 3" Hub Adaptor with O Ring (Part # 300) is the professional-grade solution for creating secure, leak-free connections on RV holding tanks and fresh water systems. Designed for 3.75" hole sizes, this hub adaptor features an integrated O-ring seal that ensures reliable performance in demanding mobile environments where vibration and temperature changes are constant challenges.

Features & Specifications

• Precision Fit: Engineered for 3.75" (3 3/4") hole size with exact tolerances for proper sealing
• Integrated O-Ring Seal: Pre-installed O-ring provides superior leak protection compared to gasket-only designs
• OEM Grade Construction: Manufactured by CPI (Elkhart Plastics) to original equipment specifications
• Durable Materials: High-impact plastic construction resists cracking, UV damage, and chemical exposure
• Lightweight Design: Only 0.8 lbs for easy handling during installation
• Universal Compatibility: Works with standard 3" plumbing connections on RV tanks
• Part Number 300 (500288): Direct OEM replacement for factory-installed fittings

Why Choose the CPI 3" Hub Adaptor with O Ring?

When you're replacing or upgrading RV tank fittings, the quality of your hub adaptor directly impacts system reliability. The CPI 3" Hub Adaptor with O Ring eliminates common failure points found in inferior fittings. The integrated O-ring design creates a compression seal that maintains integrity even as your RV travels over rough roads. Unlike cheaper alternatives that rely solely on threaded connections, this hub adaptor's O-ring provides a secondary seal that prevents leaks before they start. CPI's reputation for manufacturing OEM-grade RV components means you're installing the same quality fitting that RV manufacturers trust in new production.

Compare 3" RV Tank Fittings

Choosing the right tank fitting depends on your hole size, installation method, and sealing requirements. Here's how the CPI Hub Adaptor compares to other popular 3" fittings:

Pro Tip: Always measure your existing hole size before ordering. The 3.75" hole size is standard for many RV tanks, but verify your specific application to ensure proper fit.

Technical Specifications

• Part Number: 300 (also known as 500288)
• Manufacturer: CPI (Elkhart Plastics)
• Connection Size: 3" hub diameter
• Required Hole Size: 3.75" (3 3/4")
• Overall Dimensions: 3" diameter hub
• Weight: 0.8 lbs
• Material: High-impact plastic with integrated O-ring seal
• Color: Standard tank fitting color
• Application: RV holding tanks, fresh water tanks, gray water systems
• Installation: Requires 3.75" hole saw for new installations
• Compatibility: Standard 3" plumbing connections

What's Included

• 1x CPI 3" Hub Adaptor (Part # 300)
• 1x Pre-installed O-Ring seal
• Manufacturer's quality guarantee
• OEM-grade construction for reliable performance

Compatible Models & Alternatives

This hub adaptor works with any RV tank requiring a 3.75" hole fitting. If you need a different hole size, consider the CPI 3" Flex Black Rubber Tank Fitting (Part # 93) for 3.875" holes, or browse our complete RV Tank Fittings Collection for other sizes and styles.

Need to replace just the O-ring? We also carry the O-Ring ONLY for 3" Hub Adaptor (Part # 300-O'RING) for maintenance and repairs.

Frequently Asked Questions

How do I install the CPI 3" Hub Adaptor?

Installation requires a 3.75" hole in your tank wall. Insert the hub adaptor from the inside of the tank, ensuring the O-ring is properly seated. Secure from the outside using the appropriate threaded connection or clamp. Always test for leaks before putting the tank into service.

Is this compatible with my RV's holding tank?

This hub adaptor fits any RV tank with a 3.75" hole size and 3" plumbing connections. It's a universal OEM-grade fitting used by many RV manufacturers. Measure your existing hole or check your tank specifications to confirm compatibility.

What's the difference between this and the rubber flex fitting?

The hub adaptor (Part # 300) uses a rigid plastic construction with an integrated O-ring seal, ideal for standard installations. The flex rubber fitting (Part # 93) offers more flexibility and vibration dampening but requires a slightly larger 3.875" hole. Choose based on your specific installation requirements.

Can I replace just the O-ring if it wears out?

Yes, replacement O-rings are available separately as Part # 300-O'RING. Regular O-ring replacement during routine maintenance can extend the life of your hub adaptor and prevent leaks.

What tools do I need for installation?

For new installations, you'll need a 3.75" hole saw. For replacements, basic hand tools to remove the old fitting and install the new one. Always follow proper safety procedures when working with tank systems.

Is this fitting suitable for fresh water tanks?

Yes, the CPI 3" Hub Adaptor is suitable for fresh water, gray water, and black water holding tanks. The materials are safe for potable water applications and resistant to the chemicals used in RV sanitation systems.

Why Buy from Elkhart RV Parts?

Elkhart RV Parts is your trusted source for authentic OEM-grade RV components. We stock only verified genuine parts from authorized manufacturers like CPI (Elkhart Plastics). Every hub adaptor we sell meets or exceeds original equipment specifications. Our team understands RV systems and can help you find the right parts for your specific application. We offer fast shipping, secure packaging, and a satisfaction guarantee on all products.