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  • Writer's pictureDanny Klos

Refrigeration Suction Line Piping Practices and the Proper Use of P-Traps for Refrigerant Oil Return

Updated: 6 days ago

When it comes to ensuring the efficiency and longevity of commercial refrigeration systems, proper piping stands as a cornerstone of operational excellence. At Tri-Point Refrigeration, where your cool is our commitment, we understand the intricacies involved in setting up these systems for optimal performance. This guide delves into the critical aspects of properly piping a commercial refrigeration system, with a special focus on the pivotal role of P-traps.

Tri-Point Refrigeration Owner Danny Klos in image talking about refrigeration p-traps

Watch our video on YouTube from Danny Klos, Owner of Tri-Point Refrigeration talking about refrigeration p-traps.

Understanding Refrigeration Piping

The primary function of refrigeration piping is to facilitate the flow of refrigerant between the system's components, such as the compressor, evaporator, condenser, and expansion device. This circulation is vital for the refrigeration cycle, enabling the absorption and rejection of heat, which, in turn, cools your commercial spaces or refrigeration walk-in coolers and freezers.

Key Considerations for Proper Piping

  • Pipe Sizing: Correct sizing is essential to minimize pressure losses and ensure adequate oil return to the compressor. Undersized pipes can lead to increased pressure drops, reducing system efficiency and capacity. Oversized pipes, while less common, can cause velocity to drop too low for effective oil return, potentially damaging the compressor.

  • Pipe Layout: The layout should minimize bends and fittings to reduce pressure drops. When bends are necessary, ensure they are as gradual as possible. Also, consider the thermal expansion and contraction of pipes, providing enough flexibility to accommodate these changes without causing stress or leaks.

  • Insulation: Proper insulation is crucial for minimizing energy loss, especially in suction lines that carry cool refrigerant gas. Quality insulation reduces condensation and heat gain, improving overall system efficiency.

The Role of P-Traps

P-traps play a crucial role in refrigeration piping, especially in systems with long suction lines or lines that must navigate through different elevations. Here are the key benefits and considerations for using P-traps in your system:

  • Preventing Oil Trapping: In refrigeration systems, oil naturally circulates with the refrigerant. However, in certain piping configurations, oil can accumulate in low points, reducing system efficiency and potentially causing compressor failure. P-traps help maintain oil velocity, ensuring it continues to move back towards the compressor.

  • Facilitating Proper Refrigerant Flow: Properly placed P-traps aid in maintaining the correct flow of refrigerant, especially in vertical suction lines where the risk of oil accumulation is higher.

  • Installation Considerations: P-traps should be installed at the base of each vertical riser to ensure adequate oil return. The size and placement of P-traps must be carefully calculated based on system size, pipe diameter, and the vertical distance the refrigerant must travel.

Best Practices for P-Trap Installation

  • Regular Spacing: In systems with long vertical risers, install P-traps at regular intervals (typically every 15 to 20 feet) to ensure consistent oil return.

  • Proper Sizing: The P-trap size should match the suction line size to maintain proper refrigerant velocity.

  • Strategic Placement: Besides vertical risers, consider P-traps at the evaporator outlet and before the suction line enters the compressor room, especially if there's a significant elevation change.


Proper piping and the strategic use of P-traps are essential for the efficiency, reliability, and longevity of commercial refrigeration systems. By adhering to these principles, you ensure your system operates at peak performance, maintaining the cool that's our commitment to you at Tri-Point Refrigeration. Always consult with a refrigeration professional to tailor these guidelines to your specific system requirements, ensuring your commercial refrigeration system runs smoothly for years to come.

For a direct line to any of our teammates ready on the line to help you, call us today!

Tri-Point Refrigeration, Inc.

Austin, Texas - (512) 651-4565

118 Iron Road Suite 100

Hutto, Texas 78634

Lubbock, Texas - (806) 686-0050

13805 Avenue P Unit B

Lubbock, Texas 79423

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