How to Vacuum a Mini-Split System: A Comprehensive Guide

Vacuuming a mini-split system is a crucial step in the installation process, ensuring the removal of air and moisture from the system to optimize its performance and longevity. This comprehensive guide will walk you through the step-by-step process of properly vacuuming a mini-split system, providing you with the technical expertise and hands-on approach required for a successful DIY project.

Preparing for Vacuuming

Before you begin the vacuuming process, it’s essential to ensure that the mini-split system is properly pressure-tested to check for any potential leaks. This can be done by connecting a valve core removal tool to the system and removing the valve core to inspect for any signs of leakage.

Pressure Testing the System

  1. Attach the valve core removal tool to the mini-split system’s service ports.
  2. Remove the valve cores to allow the system to be pressurized.
  3. Use a refrigerant recovery machine or a nitrogen tank to pressurize the system to the manufacturer’s recommended pressure.
  4. Carefully inspect the system for any signs of leaks, such as hissing sounds or bubbles forming around the connections.
  5. If any leaks are detected, address them before proceeding with the vacuuming process.

Connecting the Vacuum Pump and Micron Gauge

how to vacuum mini splitImage source: Flickr

To effectively vacuum the mini-split system, you’ll need the following tools:

  • Vacuum pump
  • Hoses
  • Micron gauge
  • Valve core removal tool

Connecting the Vacuum Pump

  1. Attach the vacuum pump to the mini-split system’s service ports using the appropriate hoses.
  2. Ensure that the hoses are securely connected and that there are no kinks or obstructions that could impede the vacuum flow.
  3. Connect the micron gauge to the system, either directly or through a manifold, to monitor the vacuum level during the process.

Selecting the Correct Hoses and Fittings

  1. Use high-quality, flexible hoses designed for HVAC applications to ensure a tight seal and prevent any leaks.
  2. Ensure that the hose fittings are compatible with the mini-split system’s service ports and the vacuum pump’s connections.
  3. Consider using a manifold with multiple ports to connect the vacuum pump, micron gauge, and any other necessary equipment.

Performing the Vacuum Process

With the system properly prepared and the equipment connected, you can now begin the vacuuming process.

Turning on the Vacuum Pump

  1. Start the vacuum pump and allow it to run for a sufficient amount of time to remove air and moisture from the system.
  2. Monitor the micron gauge closely to ensure that the vacuum level is decreasing steadily.
  3. Aim to achieve a vacuum level of 500 microns or less for a brand-new mini-split installation.

Monitoring the Micron Gauge

  1. Closely observe the micron gauge readings throughout the vacuuming process.
  2. Ensure that the vacuum level continues to decrease and does not start to rise, which could indicate a leak in the system.
  3. If the vacuum level starts to rise, turn off the vacuum pump and inspect the system for any potential leaks.

Performing a Standing Vacuum Test

  1. Once the desired vacuum level is reached, turn off the vacuum pump and monitor the micron gauge readings for a set amount of time (typically 30 minutes to an hour).
  2. The vacuum level should remain stable, indicating that the system is properly sealed and ready for the next step in the installation process.
  3. If the vacuum level starts to rise, there may be a leak in the system that needs to be addressed before proceeding.


Properly vacuuming a mini-split system is a critical step in ensuring its optimal performance and longevity. By following the detailed steps outlined in this guide, you can confidently tackle this DIY project and ensure that your mini-split system is ready for a successful installation and operation.

Remember to always refer to the manufacturer’s instructions and safety guidelines, and don’t hesitate to seek professional assistance if you encounter any issues or have concerns during the vacuuming process.


  1. Vacuum Pump and Micron Gauge Demonstration
  2. Standing Vacuum Test on Mini-Split
  3. Proper Vacuum Pump and Micron Gauge Usage
  4. Vacuum Pump and Micron Gauge Troubleshooting
  5. Mini-Split Install with Vacuum Pulled to Only 20 Microns