Air Compressor Leaking Air? Here’s 5 Causes, With Fixes

If you use an air compressor at home—or work, for that matter—you know that leaks are very common. But why is your air compressor leaking air and what can you do to fix it?

If that’s your question, you’ve come to the right place. This article will help you understand the multiple reasons and provide you with the steps to correct the problem. So keep reading!

An air compressor that lacks the air necessary to do its job is useless—but that doesn’t mean it’s time to kick it to the curb.

The following should help you determine where your leak originates and, in many cases, provide you with a simple fix. 

Most Common Reasons for Air Compressor Leaks 

1. Leaky Tank

Water accumulates when compressed air sits in the tank, and if not properly drained will lead to corrosion and rust. Pinholes will eventually develop and cause both water and air to leak.

If the pinholes aren’t dealt with, they will simply get biggerand your tank will no longer be able to hold air. So it’s important to diagnose and fix them as soon as possible. If not, very soon you’ll need to buy a new compressor.

Solution. First of all, a word of warning. If your tank is badly rusted or damaged it should not be patched or welded. Anything more than pinholes fixes or sealing weak seams increases the risk of explosion.

You’ll need the following items to fix your tank:

  • Angle grinder
  • Brazing rod and torch
  • PTFE tape
  • Protective gloves and glasses
  • Wrench

After finding the leak, turning off the power, releasing all the air, and waiting for it to drain, follow these steps.

Step 1.
Using the angle grinder grind the area around the leak until it’s smooth and the surface is flush.
Step 2.
Using the brazing torch and rod, start to rebuild the area around the leak, letting the metal from the rod melt, set, and seal the leak. Wait until it’s completely cool before turning the air compressor back on.

2. Leaking Unloader Valve

The unloader valve is attached to the compressor with a pressure switch. When the pressure reaches its required setting the valve closes and seals the air back inside.

Unloader valves age with wear and tear, and the rings on the valve loosen. When this happens, the air is no longer sealed inside.

Air compressor Unloader Valve
If air continuously leaks out of the unloader valve when the air compressor is running, then the unloader valve itself is the one that has failed.

Solution. On a reciprocating air compressor, the unloader valve is typically inside of or attached to the compressor pressure switch. If you have an external unloader, you’ll be able to feel the air leaking out around the valve.

To fix it, follow these steps:

Step 1.
Unplug the compressor.
Step 2.
Drain any remaining air from the tank.
Step 3.
Remove all lines that are connected to the tank’s check valve.
Step 4.
Remove the tank check valve and inspect it. Clean or replace as necessary.
Step 5.
Test your compressor. If the check valve is properly working, when the compressor unloads, air should stop leaking out from under the unloader valve.

3. Damaged Pressure Switch Diaphragm

If you’ve fixed or determined that your unloader valve isn’t the cause of your leak, then it could be because of your pressure switch. The pressure switch has a diaphragm inside that over time will either crack or develop rusty holes.

Solution: Disassemble your pressure switch and replace the diaphragm.

Check out the video below for a visual.

4. Faulty Check Valve

The check valve on your air compressor prevents air from the back flowing into your tank. However, if the valve is damaged your tank will leak air from around it.

Solution. Here’s a step-by-step on how to fix a faulty or damaged check valve.

Step 1.
Power off your compressor and drain the air.
Step 2.
Unscrew the pressure switch fitting and disconnect the pressure switch tube from the check valve.
Step 3.
Disconnect the outlet tube fitting and tube from the check valve.
Step 4.
Unscrew and remove the check valve from the tank.
Step 5.
Install a new check valve into the tank, making sure to fully tighten and align the fitting to the pressure switch tube.
Step 6.
Reinstall the outlet tube on the check valve.
Step 7.
Power on your air compressor and test.

You can follow a step-by-step video tutorial in the following:

5. Leaking Tubes or Hoses

One of the most delicate components of your air compressor is the tube or hose. But in this case, the only time your compressor leaks from tubes or hoses is when it’s running. If the compressor is turned off there’s no air running through the hose.

Solution. If you find a leak in the hose, cut out the section with the leak and then re-couple the two segments. You can find hose repair kits on Amazon or Home Depot and the like.

How to Detect a Leak in Your Air Compressor

In many cases, you’ll be able to locate the leak simply by where the sound of hissing air is coming from.

However, you can also use soap or detergent. Putting soap around the valves and on the hoses and then starting your compressor will cause bubbles to form wherever there is a leak.

Hand Using Air Compressor
Some air leaks cannot be easily heard by human ears, so it would be also helpful to have an ultrasonic acoustic leak detector on hand.


For the most part, detecting and fixing a leak in your air compressor is fairly cheap and simple.

However, if you have a tank that is significantly rusted or otherwise damaged you should not try to fix it by welding it, as it can explode the next time you use it. If this is your situation, your alternative is to buy a new compressor.

Hopefully, you’ve been able to find an answer to your problem here. Why not check out our related posts below to see if there’s something else we can help you with?