Air Compressor Drain Valve Open or Closed

Air compressor drain valve open or closed

When it comes to operating an air compressor, there is no one-size-fits-all answer to the question of whether or not to keep the air compressor drain valve open or closed. Some air compressor manuals recommend leaving the drain valve open at all times, while others recommend closing it when the unit is not in use. According to the Central Pneumatic brand manual from Harbor Freight, it is recommended to leave the drain open during prolonged storage in order to prevent corrosion and rust. This article will discuss whether you should keep the drain valve open or close when the compressor is not in use.

What is the solution?

I’ve investigated this matter over several days and have come across a considerable debate on the subject. Some suggest leaving the drain valve open, while others argue for closing it. Based on my research, I recommend keeping the valve closed. However, it’s crucial to ensure that the air tank is sufficiently dry before doing so.

A recommended practice is to leave the drain valve open for at least one day to allow moisture inside to dry when storing the compressor for an extended period, such as one month or longer. Afterward, you can safely close the valve to prevent any foreign objects from entering through it.

I’ve explored various online discussions about this issue, and some individuals recommend leaving the drain valve open. Let’s understand how metal starts to corrode. Rust, also known as iron oxide, develops when iron or steel comes into contact with oxygen. This corrosion process happens as metal atoms lose electrons to oxygen atoms, resulting in the formation of an oxide layer on the metal’s surface. When oxygen in the air combines with metal, it creates iron oxide.

Therefore, if the air compressor tank remains open for an extended period, there’s a significant risk of internal rusting. Keeping the drain valve open exposes it to air, potentially accelerating the rusting process.

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The controversy I have collected

Air compressor drain valve open or closed controversy

Importance of water drainage

If you have an air compressor, you know that it’s important to drain the water from the tank on a regular basis. It is one of the important part of air compressor maintenance. Otherwise, the water will rust the tank and cause other problems. However, if you simply close the drain valve after draining the water, you’re not giving the water on the surface of the tank a chance to dry.

As a result, it will eventually build up and start to cause problems. To prevent this, make sure to open the drain valve and let the air circulate for a few minutes before closing it again. This will allow any residual water to evaporate, preventing it from causing damage to your air compressor.

Draining water from an air tank is very easy

If you have an air compressor, it’s important to drain the water from it after each use. Water can build up in the compressor over time and cause rust and other damage. Simply open the valve and let the water run out. In order to open the drain valve, simply turn it counterclockwise until it’s completely open. Once you’re finished using the compressor, remember to close the valve by turning it clockwise.

The best way to drain water is to tilt the compressor (if the compressor is small enough to tilt) so that all the water comes out. This may take a few tilts, but it will ensure that all the water is removed. By following these simple steps, you can help keep your air compressor in good working condition.

For hassle free drainage, you may install an electric automatic drain valve

Installing an automatic drain valve is an easy way to make sure that your tank is kept free of water. These valves open and close at set intervals, allowing the water to drain out while keeping the air in. As a result, you’ll never have to worry about your tank becoming full of water again.

Water drainage frequency

While the frequency with which you need to drain your air compressor will vary depending on factors such as the ambient temperature and humidity levels, as a general rule, it is a good idea to drain the unit after every use.

If you notice that your air compressor is struggling to reach its target pressure, or if the air coming out of the unit seems wet, then it is likely time to drain the unit. Industrial air compressors deposits more water compared to small home use air compressors. To do so, simply turn off the power and release any pressure that has built up inside the unit. Then, open the drain valve and allow all the water to run out. If the compressor is for nail guns, drain it as frequently as possible because water may cause problem to the guns if they are subject to water.

If your air compressor is equipped with an automatic drain valve, then you can simply set it to drain on a regular basis. By following these simple tips, you can help keep your air compressor in good working condition.


My suggestion is to keep the drain valve closed. You may have a different opinion on whether to leave the air compressor drain valve open or closed. Please contact us through our web page if you have any further suggestions to share.

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