Leaving an air compressor full of compressed air, or knowing whether you can or not is a regularly asked question within the air compressor community. This article will provide you with all the relevant information on leaving pressurized air within an air compressor system.

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Can You Leave an Air Compressor Full?

In other words, can you leave an air compressor system pressurized? Yeah, you can, but I will not recommend it. It is perfectly safe to leave an air compressor full of pressurized air as long as the air compressor system itself has been properly maintained. It would be necessary to regularly drain the tank of moisture that will naturally accumulate, otherwise, you run the risk of the insides corroding and the compressor tank no longer being “safe”.

During the regular duty cycles (use) of an air compressor, a fully pressurized air compressor is standard. But, in the case that the air compressor is not in use for an extended period of time then the air compressor should be drained and shut off. Condensation build-up and water corrosion is the most common reason for an air compressor tank failing, so why would you not opt to eliminate this risk?

Why is it Necessary to Drain the Air Compressor?

Air carries natural water vapor particles within itself, and so when air is compressed and the air is heated significantly, these water vapor particles condensate and create moisture. Over a certain length of time, the condensation accumulates and water eventually builds up at the bottom of the tank.

If this moisture is not captured by a filter, water separator, or drained from the system, it can not only damage the air compressor tank but also the piping system, and even damage your air tools. So, how often should you drain the air compressor? Many people recommend draining the air compressor after each use but this can depend on how frequently you use it.

Others recommend draining the air compressor once a week if you use it daily, as you’ll be using the air the next day so draining it may not be as essential. This can also save you the power to restore a full tank. If you don’t use the compressor as regularly then you should drain it after each use. Stored air will increase the chance of rust and as a result, it will cause your compressor to deteriorate and become less safe to use a lot faster.

Most manufacturers will provide a recommended maintenance routine in their user manuals, and within there should be a guideline on how frequently you should drain your air tank, typically advised as a daily activity. If your compressor pump only cycles a few times a day, you should still aim to drain your compressor’s tank every other day or several times a week. This will help to prolong the operating life of the compressor and protect your pneumatic tools.

Visit our How Often To Drain Air Compressor Tank guide for more information!

Reader Comments & Responses

Should you leave air in an idle compressor?

by Pierre
(North Bay Ont Ca)

Air left in compressor for two months while idle. Problem?

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Pierre, the ideal scenario is to open the tank drain to bleed off all air, and all the water that has accumulated in the tank during use, so that the tank is dry while in storage.

Else, your tank will eventually rust.

Does that bother you? Is the fact that your tank might get a rust hole in it faster if you don’t drain it than if you do important?

Only you can decide.

Me, I try to drain my tank regularly, and only leave air in it, if I’m using it the next day.

Compressor Air Tanks Www.about-Air-Compressors.com
Compressor Air Tanks www.about Air Compressors.com

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Leaving tank pressurized
by: Doug

So If at the end of the day compressor has been off for hours I would assume that the air temp had fallen to room temp. Can You simply open drain for 10-20 seconds to push out moisture and close up to save the compressed air for another day?

Is that OK to leave it pressurized and will not rust or is it best to drain tank completely to remove all compressed air even if it has cooled off and the water vapor has condensed to liquid?

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Ultimately, the compressor tank will rust through regardless.

By draining regularly, you defer the date you have to replace the tank or compressor.

Electric auto drains do what you suggest by cycling open periodically for a fixed period.

So yes, if you open the drain until water and mist stop flowing out, and if you still have air in the tank, close the drain to save the air.

That’s what I do.


If you have any questions about leaving an air compressor full, please leave a comment below, with a photo if applicable, so that someone can help!