Why and How To Drain Air Compressor?

How and why should you drain water from compressed air tanks? As we all know, the air contains a lot of moisture and impurities. During the compression process, some water vapor may condense in various parts of the air compressor.

This situation is particularly serious in the air compressor tank. If the condensed water is not handled in time, it will cause rust and corrosion inside the air compressor, reduce the energy efficiency of the air compressor, and reduce the quality of compressed air. Therefore, it is very important to regularly drain the exhaust gas and condensed water in the air compressor. So how to drain air compressor? Let Kotech introduce it to you.

Why should you drain water from compressed air tanks?

why should you drain water from compressed air tanks

Causes of water in air compressor

There is water in the air, which is the so-called “humidity” of the air. After the air is compressed, it will become supersaturated, and the water in the air will precipitate and exist in liquid form. The moisture content in the compressed air is related to the humidity of the air. For example, if the environment in the machine room is too humid or due to seasonal reasons, the water content in the air will exceed.

Liquid water is produced during the compression process. When the air compressor is running, the internal temperature is high, and the water molecules in the compressed air form water vapor. This is a natural and inevitable byproduct of the air molecules being squeezed together. Water can gather in almost any part of the compressor system, including pipes and pneumatic tools themselves, but the most common area for moisture accumulation is the air receiver (air tank).

As the air tank not only provides buffering and storage for compressed air, but also plays a role in cooling compressed air. The water vapor in the compressed air liquefies and falls into the air tank after the temperature drops. Over time, a large amount of condensed water will accumulate in the air tank.

Lack of corresponding specialized compressed air drying equipment, no corresponding dryer is installed or it does not work properly after installation (the drying equipment fails and is not discovered and handled in time).

The air compressor’s own drainage measures fail. Sometimes the air compressor’s own automatic drain is blocked or the air tank’s automatic drain is blocked, which can also cause a large amount of water to accumulate in the air compressor. (Generally, the air compressor’s own drainage can only guarantee the basic drainage function)

The hazards of water in air compressor

If the water in the air compressor accumulates to a certain height, it will not only affect the gas storage capacity of the air tank, but also affect the quality of the compressed air. If it is in a relatively humid area or weather, there may be a large amount of water in the air compressor tanks for a long time. If the minimum pressure valve of the air compressor happens to fail at this time, the water in the air tank may also flow back into the air compressor cylinder along the air inlet.

In the long run, it will cause the air compressor to rust and corrode, the air compressor energy efficiency will decrease, the compressed air quality will decrease, and more severe problems such as air compressor overload tripping. Know more about air compressor overload tripping.

In colder areas or weather, the condensed water in the air compressor may freeze, which may cause pipe blockage or break, etc., resulting in serious safety risks.

In addition, in most applications that require the use of compressed air, water is considered a contaminant that affects the products you make with compressed air. In food, beverage, medicine, or precision work such as dentistry or painting, delivering water to products and materials may cause very serious problems.

In these industrial fields, water, like impurities such as oil and dust, are intolerable. So this is why you should drain water from compressed air tanks regularly.

how to drain air compressor

How to drain air compressor?

There are several ways about how to drain air compressor:

Shutdown drainage

Manual drainage is the most basic method of draining water from an air compressor, and it is also a commonly used method. The specific steps are as follows:

  1. First turn off the power of the air compressor, remove the air pressure accumulated in the pipeline, and then tighten the bleed valve.
  1. Find the drainage device or drain port at the bottom of the air compressor, which is usually a screw or a valve, and rotate the drainage device or open the valve to drain the accumulated water into the installed wastewater pipe.
  1. The drainage time should not be too long. Generally, the drainage time is about 10-15 seconds. When the discharged water slows down or stops, remember to close the drain valve.
  1. Close the drain device or valve, open the bleed valve, and the daily maintenance is done.

how often should you drain air tanks

Online drainage

During the operation of the air compressor, the water in the air compressor can also be drained. The advantage of draining accumulated water during operation is that the water in the drainage chamber can be cleaned in time to reduce the formation of accumulated water and the production will not be paused.

Why and How To Drain Air Compressor

However, in this way, personal protection should be taken to avoid safety accidents such as electric shock; when discharging water, the temperature should be appropriate to prevent scalding

Automatic drainage device

The air compressor also has an automatic drainage method, which can be selected according to actual conditions. Automatic drainage mainly uses sensors to detect the water level in the air compressor drainage valve port. When the water level exceeds the set value, the automatic drainage valve will open to drain water and impurities.

The main advantage of the automatic drainer is that it can intelligently sense the amount of water and automatically drain it. This method does not require manual intervention, saving labor costs. At the same time, it can increase the frequency of drainage and don’t need to worry about forget to drain the compressed air tanks.

However, the equipment and maintenance costs of automatic drainage are higher than manual drainage, and more maintenance and inspection are required to prevent the air compressor or the automatic drainage device from being blocked or unexpected conditions occur, and the device cannot drain air compressor timely.Heatless Purge Desiccant Compress Air Dryer

Install an air dryer

The main function of an air compressor dryer is to remove moisture, water vapor and impurities generated by the compressor, so that drier and purer air can be obtained. Dryers generally have two working principles. Know more about the air dryer in air compressor.

Physical drying: Physical drying is achieved by cooling water vapor to condense into water mist. This way usually uses a refrigeration dryer or an adsorption dryer.

Chemical drying: Chemical drying is achieved by using special adsorbents to absorb water vapor. It is mainly suitable for high temperature and high humidity environments.

Install after-cooler

Another option is an after-cooler, which can cool the air from 200-350°F to a usable temperature of about 15-20°F above ambient and removes most of the moisture created during the cooling process. For most applications, an air after-cooler will remove enough moisture to safely operate air tools or process product. Some filters also help remove moisture and can be installed before the air is compressed to achieve this goal.


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How often should you drain air tanks?

The accumulated water in the air compressor will affect the stability of the equipment, and reasonable drainage can ensure the operating efficiency and life of the equipment. Therefore, most air compressor manufacturers recommend draining at least once a day. It is recommended to drain the water from compressed air tanks after the end of the day’s use. If it is a continuously working air compressor, it can be drained every 12 hours.

Especially in an environment with high temperature and humidity, the accumulated water in the air compressor is more likely to form and needs to be drained more frequently. In short, try not to delay the time if you can drain it once. If the equipment is out of use for a long time, it is also necessary to remove the water to avoid long-term scale accumulation and further affect the operation of the equipment.

How to drain air compressor depends on the air compressor manufacturer and air compressor model, manual drainage or automatic drainage can be used, but during the drainage process, attention should be paid to safety measures to avoid unnecessary damage to maintenance personnel.

For example, manual drainage requires tightening the device or turning off the power supply of the air compressor to prevent the discharged water temperature from being too high, causing burns or electric shocks. When using automatic drainage, you need to pay attention to regular inspections of whether the sensor equipment is working properly and whether there is any blockage to prevent drainage failure with no one knows it.

Prevent trouble before it happens

Did you know? The “environment” of the air compressor room is also critical! Whether it is an oil free screw compressor or an oil injected screw compressor, whether it is an air-cooled air compressor or a water-cooled air compressor, the ventilation problem of the air compressor room must be solved.

According to statistics: more than 50% of the failures of air compressors are caused by ventilation and drainage. Solving the ventilation and drainage problems of the air compressor room will help reduce the problem of compressed air carrying a large amount of water from the source.

In addition, a large amount of heat will be emitted during the compression of air. If this heat cannot be discharged in time, the air compressor room will cause the room temperature of the air compressor room to gradually increase, so that the temperature of the air intake port of the compressor accessories will become higher and higher.

Such a vicious cycle will cause the exhaust temperature of the compressor accessories to be high and alarm, and at the same time, the compressed air production will be reduced because of the low density of high-temperature air.

Drain the air compressor room

Drain the air compressor room

  • Check whether the air compressor room is prone to water accumulation. Conduct a detailed survey of the foundation, geological structure, flood control facilities, emergency facilities, etc. in the surrounding areas of the air compressor room, find hidden dangers and weak links, and formulate a drainage and flood control plan for the air compressor station.
  • Check whether there is water leakage inside the air compressor room. It is easy to leak and seep water during the rainy season, which may cause short circuits. In severe cases, it may even cause accidents such as electric leakage and injury. The staff should strengthen patrols, enhance their sense of responsibility, and prevent accidents before they happen.
  • Check the working status of the air compressor post-processing. Check the post-processing facilities such as cold dryers, airtanks, and precision filters. Especially on rainy days, the air contains a lot of moisture, so make sure that the post-processing system is in working condition.

Ventilation of the air compressor room

  1. Keep the air compressor room clean and dry, and exposure and high temperature are strictly prohibited. 2. The airtank must be placed in a well-ventilated place, and welding or hot processing operations shall not be performed within a radius of 15m. 3. Before opening the air supply valve, the air pipeline should be kept unobstructed to deliver air. No one can work or stand in front of the air outlet.
  1. The air compressor room should be selected in a cool, clean, and well-ventilated place as much as possible, with an ambient temperature below 40℃ and a suitable temperature of 20-30 degrees, and ventilation should be maintained.
  1. If the ambient temperature is too high (greater than 40℃), it is recommended to take cooling measures (such as avoiding direct sunlight, opening doors and windows, etc.) to avoid unnecessary high-temperature shutdown; if the ambient temperature is low (less than 0℃), the condensation point temperature of the lubricating oil must be controlled above the ambient temperature. Not only the low temperature in summer, but also the low temperature in winter should be considered.
  1. The air inlet should avoid the sun in the west, which will cause the ambient temperature to rise and high-temperature alarm. If the factory environment is poor and dusty, a ventilation duct should be installed to lead the air inlet to a place where the air is relatively clean. The installation of the duct must be easy to disassemble and assemble for maintenance. The installation size refers to the external size of the air compressor.
  1. The cross-sectional area of the compressor exhaust hood cannot be reduced, reduced, or too many bends or too long; resulting in poor exhaust and back pressure, causing the unit to shut down at high temperature.
  1. There must be enough space around the air compressor for other components to enter and exit, and there must be at least 1500mm between the air compressor and the wall. There is a lifting device. The air compressor is more than 1500mm away from the top space.
  1. In order to be trouble-free, the compressor intake process must eliminate all particulate and air contamination. Dirt, dust and corrosive gases can cause premature wear of the air compressor. They also react negatively with the compressor coolant, thereby damaging the oil system and reducing the cleanliness of the exhaust gas.
  1. The air inlet must be set on the outer wall of the air compressor room to avoid negative pressure in the room.
  1. For areas with high dust content,pre-filters installationshould be taken into consideration.


Compressed air is the fourth largest power source in industry and is widely used in machinery, electronics, metallurgy, petrochemical, rubber, chemical fiber textile, medicine, food and other industries.

Air compressors that are not regularly maintained and exhausted and drained may cause unnecessary damage to various pneumatic machinery, instruments and pipelines, and cause shutdowns, as the compressed air they produce may contain water, oil, and dust.

It may also directly affect product quality and reduce the company’s market competitiveness. Therefore, it is critical to perform maintenance and maintenance operations regularly such as exhaust and drain your air compressor.

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