Using the Vacuum Test Plug

By Rusty


The Vacuum Test Plug allows you to vacuum test enclosures through the standard vent, ensuring a watertight seal. It fits to a 1/4″ hose and works great with most hand-operated vacuum pumps for in-the-field testing!

Parts and Tools

You Will Need

Attaching the Vacuum Plug to the Pump

1. Attach clear vacuum hose to the pump (refer to instructions for your pump).

step 1 -test

2. Install O-rings on the vacuum plug, lubricating lightly with silicone grease before installation.


3. Insert the barbed end of the vacuum plug into the vacuum hose.


Testing the Test Setup

Before testing the enclosure, it’s a good idea to test the pump, hose, and vacuum plug alone to make sure that there are no leaks in the pump, the vacuum gauge, or the hose connections. The vacuum plug comes with a rubber stopper that makes this easy! The following describes how to test these parts (i.e. “testing the test setup”).

1. Insert the rubber plug into the hole on the vacuum plug to seal it up.


2. Turn the knob on the side of the vacuum pump so it is in the “VACUUM” setting.


3. Pump the hand pump to approximately 15 inHg, and monitor for about 10-15 minutes, making sure that the pressure does not decrease by more than 0.5 inHg.

step 3 – test

If successful, this test setup is ready to use. If not, check the following:

  • Proper hose connections on the pump and on the vacuum plug.
  • The vacuum pump and vacuum gauge. You can test the pump by removing the hose and using the rubber stopper to plug the hole.

Testing the Enclosure

1. Remove the sealing plug from the vent on the watertight enclosure.


2. Insert the vacuum plug attachment.


3. Pump the hand pump, removing air and decreasing the pressure inside the enclosure to approximately about 15 inHg. This will take quite a few pumps – roughly 38 pumps for an empty 2″ enclosure, 85 pumps for an empty 3″ enclosure, and 152 pumps for an empty 4″ enclosure (using a Mityvac hand pump).

step 3 – test

4. Monitor the gauge for about 10-15 minutes and make sure the vacuum pressure does not decrease by more than 0.5 inHg.


If successful, remove the test plug, and replace with the original vent plug. If you find a leak, check the following:

  • Hair, dust, or other obstructions of the O-ring seals
  • Loose cable penetrators
  • Scratches on the inside of the tube



Rusty is the founder and CEO of Blue Robotics. His background is in engineering but he likes to be involved in everything at Blue Robotics!