Can You Leave an Air Compressor Full?

Air compressors are complex beasts, but we rely on them for a lot. It’s all the more reason why it pays to look after them as carefully as possible! If you’re like us here at Renovation Dojo, you’ll have read the instruction manual from front to back before you power on – hopefully! 

Yes, it’s technically safe to leave an air compressor full, but it’s not always the recommended action. Doing so could harm the lifespan of your compressor, as well as any tools you use with it.

Compressors arrive in different shapes, sizes and strengths, so the rules may change from unit to unit. When in doubt, consult your manufacturer. However, if you’re going to power down your air compressor for a long period, it’s best to drain it first. Let’s take a look at why.


Why should I drain my air compressor?

It’s just good practice! When you drain your air compressor regularly, you:

  • Ensure it is always working at its best.
  • Protect tools and equipment that uses the compressor.
  • Prevent corrosion from building up inside the tank.

It’s all about moisture. Air compressors swallow ambient air, which is full of moisture in varying amounts. The system pushes out vapor, which causes droplets of water to pool at the bottom of the tank. If you use your air compressor a lot, your tank is going to fill up fairly quickly.

The more water and moisture that’s in your tank, the less reliable your compressor will be with sensitive materials. As you can imagine, if you’re working with metal or wood, that will lead to all kinds of unwanted results!

Not only that, but corrosion is a major problem for many air compressor tanks. Even the best air compressors can suffer over time. By removing moisture (i.e., water) from your tank regularly, you’re keeping it running at its best.

Keep in mind, too, that moisture will also affect any accessories or connections in your tank along the way. Look after your valves, switches, and outlets!

How often should I empty my air compressor?

How often you should ideally empty your air compressor largely depends on how often you use it or how intensively. You also need to consider the storage temperature too – anything that’s likely to breed moisture will cause serious problems if left alone for too long.

Our advice is to try and empty your compressor after each use, particularly if you use it for extended periods of time. Otherwise, twice or three times per week is a healthy schedule. To ensure your air compressor is always working at its best, you shouldn’t leave it full for more than a few days at a time.

If your manufacturer suggests a specific maintenance schedule, it is always good to follow their lead. They will, ultimately, know best about your specific compressor – and that should take away a lot of the guesswork!

Most experts agree that the longest amount of time you should leave a compressor full of water is around a week. Left for any longer, and you are at serious risk of building up rust in the tank.

Not only that, but if you continue to use a full compressor tank with various tools and motors, you’re at risk of pushing moisture into those systems, too. Rust and corrosion aren’t contagious, but moisture spreads easily – and causes similar problems wherever it travels to.

How to drain your air compressor

New to air compression? Here’s how to drain your air compressor in a few simple steps.

Always power down

This may go without saying, but always ensure your air compressor is switched off before you try draining it. For added safety, we recommend removing the unit from your power outlet completely.

What’s more, we recommend turning down any regulator settings on the base unit to ‘0’. 

Protect yourself

While you’re only releasing moisture and condensation from your tank, there’s still a chance that dirt and debris may start spraying out! So, be sure to strap on a pair of safety goggles and a pair of heavy-duty gloves before you start.

Fully disconnect

Not only should you remove your compressor from the outlet, but you should also disconnect the air supply too. Again, it is better to be safe than sorry and ensure you only work with the basic unit.

Carefully depressurize the tank

You should ideally locate the safety valve in your compressor’s manual and find the ring pull. Most compressors come with this attachment, so it should be easy for you to pull and release.

Remove the safety valve with a gentle pull. You’ll likely find that the air you release will disperse with some force! All the more reason to wear goggles and to take things slowly.

Keep an eye on the tank’s pressure while releasing air, and reattach the safety valve once below a safe level. That’s normally 10 PSI for most compressors.

Drain the moisture

Again, refer to your manual to find the drain valve – but this should be easy to spot, as they are generally turn-release handles. If you’re using an older model, you might need a wrench.

Turn the drain valve gently at 90 degrees until the moisture completely drains from the tank. Then, be sure to reseal the valve tightly – if you don’t, your compressor won’t work as you expect it to.

Business as usual

You’re done! Now reattach your supply, re-establish the pressure, plug in and power on. It’s good to go.

Should I buy an automatic drain valve?

Automatic drain valves are very popular for the obvious reason that they don’t need much attention! These tend to start draining as soon as moisture reaches a specific level. They sometimes arrive built into compressors or are available as add-ons for various models.

It’s not essential to fit an automatic drain valve unless you find draining a chore time and again. However, if you’re working to a regular schedule, you’ll likely save money by sticking to manual draining.


Can you leave an air compressor full? You can, but if you value the lifespan of your unit, you’ll make sure to drain it regularly!

Of course, different manufacturers, models, and usages will change the answer from case to case. So, follow your manufacturer’s advice – but always be sure to empty a couple of times per week for the best results.