Aquarium Pump Adapter (1.25”) + Venturi Option

While building out a custom sump, I ran into a common issue—most return pumps claim to support larger fittings, but the included adapters bottleneck the outlet.

My system was already plumbed for a 1.25” return line, so instead of reducing flow at the pump, I designed this female threaded adapter to maintain full diameter from the source.

During that process, I also created a second version with a built-in air intake (venturi) for use in a DIY protein skimmer.

Both versions are included.

Included Models

• Standard Adapter – 1.25” female threaded outlet
• Venturi Adapter – Same fitting with integrated air intake port

Key Features

Full-Flow Design

Maintains a true 1.25” outlet to avoid restricting return flow at the pump.

Broad Compatibility (Tested)

Designed around a common thread size found on multiple pumps.

Tested to fit:

• Jerepond pump (shown)
• XpertMatic pump (shown)
• Additional pump with matching threads

May fit other pumps using similar outlet threading, but not guaranteed.

Integrated Venturi Option

The venturi version includes a side port designed for:

• 3/8” ID vinyl tubing

Perfect for:

• DIY protein skimmers
• Air injection setups
• Experimental filtration builds

Clean, Functional Geometry

• Smooth internal transitions to reduce turbulence
• Thick walls for durability
• Easy to print and install

Print Recommendations

• Material: PETG recommended
• Preferred: ABS or Polycarbonate for long-term use
• Walls: 4+
• Infill: 25–40%
• Supports: Not required

Fit Notes

• Designed for pumps with standard threaded outlets
• Thread fit is snug by design—may require minor tuning depending on printer/material
• If needed, scale slightly or chase threads for a perfect fit

Use Cases

• Maintain full flow in return lines
• Replace undersized OEM fittings
• DIY sump builds
• Protein skimmer venturi intake

Important Notes

• Not all pump threads are standardized—verify fit before permanent use
• Do not overtighten (printed threads can strip)
• Always leak test before installing in a running system

System Integration

This model is part of a larger custom sump build, including:

• Media cup system
• Media cup tray
• Tank modifications

Check my profile for the full setup if you're building something similar.

License

• Personal use only
• Do not sell prints
• Do not repost files to other platforms

Final Thought

This started as a simple fix to avoid bottlenecking my return line, but turned into a versatile adapter that works across multiple pumps and even supports venturi-based setups. If you’re tired of undersized fittings, this should help.