How to Check for Leaks in a Vacuum System

What You'll Need
Small spray bottle

Finding a leak in a vacuum system can be a little like finding the proverbial needle in the proverbial haystack. However, there are certain things you can do to make finding leaks in a vacuum system much easier. These certain things can be divided into 3 basic categories.

Step 1 - Look for Obvious Breaks

Your eyes are one of the world’s best diagnostic tools available to you. You just have to know what to look for. If you think there is a leak in a vacuum system with flexible lines, flex the line in every direction possible and look for cracks or holes in the lines. It’s important to remember that there may be more than one point on the vacuum line that is leaking, so it’s important to remember to check the whole length of the vacuum line, from source to terminus.

Also, thoroughly inspect connection points for proper fit. Make sure there aren’t any dents in metal fittings. If there should be gaskets at the connections, check to make sure they are in serviceable condition. Make sure all connections are properly connected and secured. This last point means to look at the connection and then also physically check the connection by either wiggling it to see if it is lose, or pulling the connection and firmly reconnecting it.

Step 2 - Listen for Leaking Air

Any leak in a vacuum system is going to produce a tell tale hissing sound. How loud that hissing is depends on the size of the leak and the vacuum pressure generated by the vacuum pump system. Turn off as many generators of ambient noise as you can and turn on the vacuum system. Walk from the vacuum source to the terminus, or end of the vacuum line. As you walk the vacuum hose or line, move it around to attempt to stimulate the point of leak to make more noise, making it easier to hear.

One tip for this step would be to plug off the end of the vacuum line at the end farthest from the source. Plugging the line will exert more vacuum on the leak, causing it to be louder. If this doesn’t help, then get yourself a small spray bottle and fill it with water. With the vacuum system exerting vacuum in the lines, spray the line and listen for a gurgling sound in addition to the hiss of the vacuum leak.

Step 3 - Feel for the Leak

For this step, you need to lightly grasp the vacuum system line with the system energized and exerting vacuum within the lines. Slowly run your hand from the source to the end of the vacuum system line. Moistening your hand will help find the leak using this method due to the evaporative cooling effect of air moving across a wet body part.