Don’t Let Your Air Compressor Get Wet or Rained On: Here’s Why

Everyone knows that leaving tools out in the rain is a sure-fire way to ruin them – and air compressors are no exception. Though they may seem like heavy-duty pieces of equipment, if there’s one thing that can ruin an air compressor in a hurry, it’s moisture. In this article, I’ll tell you everything you need to know about why you shouldn’t let your air compressor get wet.

What Can Happen If Your Air Compressor Gets Wet?

If an air compressor gets wet (whether from rain, flooding, spills, etc.), it can affect performance, accelerate wear, or cause the unit to stop working entirely. Excess moisture can damage or degrade mechanical components, both internal and external. It may also create electrical/fire hazards.

To understand how destructive water can be for an air compressor, let’s look at the different ways moisture can affect its components and ability to function.

Corrosion & Rust

Since air compressors are constructed mostly with metal components, they are susceptible to corrosion and rusting. This is why the air tank needs to be drained of condensate after each use – corrosion can degrade the tank and potentially result in an explosion. The tank exterior may not be in as much danger – unless its paint coating is damaged – but other external components are at risk. 

Small metal components such as tank drain plugs, air relief valves, and hose connectors are typically made of brass, which does not rust. However, brass can still corrode when exposed to moisture. This corrosion can cause air leaks or seize valves, which can wear down the motor or cause dangerous over-pressurization, respectively.

If even a small amount of water makes it inside the pump (likely through the air intake vent), it can also corrode the air chamber, discharge valve, unloader valve, and pistons (or rotary screws, depending on the type of compressor you have).

Electrical Issues

Likewise, if water comes in contact with electrical components such as contact terminals or motor windings, it can corrode them and cause electrical malfunctions. 

But aside from corrosion, the air compressor’s electrical components can suffer more immediate (and dangerous) effects when exposed to moisture.

Water can cause short-circuits within the pump motor, frying the electrical components or potentially causing an electrical fire. And since water is conductive, a wet air compressor can even cause electric shock in some cases. For these reasons, it’s vital not to attempt operation while the compressor is wet.

Pump Issues

If liquid gets into the pump as described above, it can also cause serious issues if the unit is turned on. Unlike air, liquid cannot be compressed. So when the pistons work to compress the air in the air chamber, any liquid in the cylinder will prevent the piston from completing its full stroke, simultaneously putting an extra load on the motor. 

This can cause immediate damage to the cylinder head, piston, connecting rod, crankshaft, and inlet and outlet valves, as the air chamber becomes over-pressurized. It may also cause the motor to overheat or burn out. 

And if any water in the air chamber seeps down into the cylinder, it can interfere with proper lubrication and increase wear and tear on mechanical components.

Water In the Air Hose

Another possible consequence of letting your compressor get wet is getting water in the air hose. This is mainly a concern if your air hose is coiled up on the ground or the tool attachment is submerged. If you attempt to use the compressor while there’s water in the hose, that water will come out with your compressed air. 

This may not be a huge issue if you’re using a pneumatic wrench (though it may corrode the wrench itself – not to mention scare the daylights out of you when it spurts out), but if you’re filling a tire or applying paint, the last thing you want is water in the line.

What To Do If Your Air Compressor Gets Wet

Not that you know what water can do to your air compressor, it’s easy to see why it’s so important to keep it dry. But if you’re reading this because your compressor already got wet, you’re probably wondering if it’s too late to save it. Well, not necessarily.

If Slightly Wet

If your compressor only got a little wet – something was spilled on it, water from a leaky roof dripped on it, it got rained on briefly before you ran out and rescued it, etc. – you probably don’t have too much to worry about. 

First, make sure it’s unplugged. Then, you’ll want to dry it off the best you can with a dry cloth to get any excess water. Next, it’s a good idea to check if water got into the internal components. Take out the intake air filter and see if there’s any moisture on it or in the filter housing. If so, let it dry, leaving the filter housing disassembled.

You’ll also want to examine electrical components for moisture. Your user manual should contain instructions for how to access these. Leave the cover/access panel off and let the compressor dry out for at least a day or two in a climate-controlled environment. You can use a small fan to help speed up the process (as long as the space isn’t too dusty) – but avoid using anything that produces heat, such as a blow dryer.

Once a day or two has passed and everything appears dry, put the filter back in and turn your compressor on, monitoring it closely for sparks, unusual sounds, and performance problems. If you observe any of these, immediately shut it off from the breaker box and disconnect it from power. 

If Very Wet

If your compressor was left out in the rain for longer than a few minutes or it was even partially submerged after a flood or other mishap, that’s a different story. With so much moisture, water has likely entered the pump or soaked electrical components.

In this case, your best bet is probably to replace the air compressor. You may be able to take it to a professional repair shop, but if water has flooded the cylinder or gotten into the motor, it’s unlikely that the unit will work again. And even if it does, the internal damage can lead to a premature breakdown or even an electrical fire.

Can Air Compressors Be Kept Outside?

In general, air compressors shouldn’t be kept outside. Doing so leaves them more exposed to ambient moisture, rain, and other weather conditions that can cause wear and tear. However, if certain measures are taken to protect it from the elements, it is possible to keep your air compressor outside.

There are a few key conditions you’ll want to meet if you want to keep your air compressor outside without dramatically shortening its lifespan.

Shelter

First and foremost, you’ll want to keep your compressor housed in some sort of structure to protect it from rain, snow, and debris. It should have adequate space and ventilation to allow the compressor to keep cool.

Solid Foundation

You’ll want your compressor to be sitting on a concrete slab or other solid, level surface to prevent tipping, sinking, or exposure to moisture from the ground. It should be an area that won’t flood during a storm.

Clean Air

You’ll also want to keep the area around the compressor clean to avoid the intake of excessive dirt and dust. It’s also best to keep a close eye on the air filters and clean the compressor regularly. 

Electrical Safety

Air compressors and extension cords don’t get along very well, so you’ll want to plug the compressor directly into a GFCI-protected outlet – preferably on its own dedicated breaker.

Winterization

Extreme cold can cause a range of problems for an air compressor (particularly if moisture is involved), so you’ll want to protect it from freezing temperatures as best you can. Your user manual or manufacturer may have instructions and products to help you winterize your compressor.

But for a more involved discussion on winterization and putting an air compressor outdoors, check out this article.

In Conclusion

As you can see, it’s best not to allow your air compressor to get wet. Even excess humidity in the air can destroy it from the inside out – if you don’t empty the tank regularly, that is. The good news is, you can typically save it without costly repairs if it was only exposed to a little bit of moisture. Of course, if you have any doubts, you’re better off hiring a pro to look at your compressor and assess the damage.

Justin

Justin is a full-time blogger with a passion for anything DIY. When he's not hanging out with his wife and son, you can find him putting the finishing touches on yet another home project he's taken on. He's also the creator of AllAboutAirCompressors.com.