Why Must Air Tanks Be Drained?

If you have or have been around people who use vehicles with air brakes, it is common knowledge that air tanks need drainage. But nobody actually answers the question – why must air tanks be drained.

The air tanks must be drained because the compressed air inside has some amounts of compressor oil and water. These two substances can build up over time and damage the brakes. It is especially true when the temperature drops to the freezing point in cold weather.

Avoiding this task can even lead to dire consequences like a brake failure. If you use air brake systems, take great care of when and how often you drain the tank. Below, we have discussed this topic in detail to help you understand it better. Let’s dive in.

When Should You Drain Your Air Tanks? 

two air tanks of a truck

You should drain your air tanks when you’re done driving at the end of the day. This is suggested because air contains a significant amount of water. So even if there is not a lot of compressor oil, the moisture will still be present and cause problems in your air brakes. 

People who weren’t aware of this before should check the condition of their air brakes immediately. If they notice the slightest rust or wear in the structure, it’s time to drain the air inside. You may even want to replace the unit in case the damage is severe.

How Often Should You Drain Your Air Compressor?

As mentioned, you should drain the air compressor or tanks daily. When you’re done driving for the day, let the tank drain to avoid complications in the future. However, there are exceptions if your air brake system has an air dryer. 

It is because the dryer eliminates all the moisture content in the tank. You may not need to drain the tank for days, weeks, and even months. That said, we still recommend daily tank drainage as the dryer can’t help remove the oil. 

How to Drain Your Air Compressor

You can drain the air compressor using the manual method. However, if you have an automatic setup, there’s no need to do anything. The system will remove the excess moisture along with the rust particles on its own. 

The Manual Method

  • Switch off the air compressor unit. 
  • Release all the air pressure that is below 10psi. You can do so by pulling the ring present on the safety valve. 
  • Find the main valve at the rear of the air tank and open it. 
  • Tilt the tank to remove all the moisture or fluid. 
  • Close the valve and fix the tank back in its original position. 

Why Must Air Tanks Be Drained?

Not draining the air tanks can cause brake failure and tank corrosion. Both the consequences are harmful and inflict serious damage. Let’s discuss how below.

Brake Failure

Contrary to the name, the air compressor tanks do not just include a combination of gasses. The tank consists of some water and compressor oil as well. These two substances freeze into the valves during low temperatures.

The blockage in the air tank leads to brake system failure. A vehicle with no brake controls accounts for 5% of crashes in the US annually. That’s about 300,000-car crashes.

Fortunately, there are a few ways that you can use to identify an upcoming brake failure. These include strange noises, a spongy feel in the brake pedals, and the car pulling to one side whenever you apply brakes. Another prominent sign of brake failure is an unusually low position of the pedal. 

In addition to draining your air tanks, you’ll also want to know how to winterize your air compressor.

Tank Corrosion 

We’ve previously mentioned that the air present inside the tank contains moisture or water vapors. It means the compression of air in the tank also results in the formation of water droplets. They settle down at the tank bottom. 

Over time, the water increases in quantity. Since the air tank is a metallic structure, the rusting process becomes triggered. The metal corrodes until it is no longer functional. 

You cannot continue using a rusted air tank. The wear and corrosion can lead to air leakage. Replace the unit immediately if you notice any rusted metal.

Can Air Tanks Explode? 

Yes, air tanks can explode. However, these cases are quite rare. The leading cause behind an air tank explosion is excessive corrosion. 

The water condensate buildup in the tank can damage the metal. As a result, the contents leak into the brake system and cause an explosion. Another cause is the clogging of the tank valves due to frozen compressor oil and water. 

These substances freeze in the cold weather, which blocks important passages in the tank. As the brake system continues to function, the pressure develops inside that causes the metal to expand and explode. These incidents can be deadly. 

How Long Do Air Tanks Last? 

An air compressor tank is a robust structure made from metals. These include steel, stainless steel, and even carbon steel in premium options. They last around 10 to 15-years when well maintained.

In terms of maintenance, the air tank requires nothing more than regular drainage. But avoiding it can still lead to brake failure and corrosion. Since the unit is expensive, you’ll want to avoid frequent replacements.

What Is the Supply Pressure Gauge Used For? 

gauge attached to the yellow tank

A supply pressure gauge is a measurement device connected to the air tank or tanks. It shows the amount of pressure (a force acting on per unit of surface area) inside. The unit used to express it is psi or kiloPascals. 

It’s important to keep an eye on the air pressure levels in the tank. Since the brake system operates entirely on air, the slightest fluctuations in pressure can affect the performance. The lowering of it can lead to sudden brake failure and even accidents. 

The normal range for any single vehicle with air brakes is 100 to 120psi. You can also express it as 690 to 828kPa. Any value out of this range will get considered an abnormal condition. 

What Happens if the Air Tank Pressure Gets Too Low or High? 

Typically, an abnormal condition in the tank pressure will trigger an automatic response from either the safety valve or the low air-pressure warning device. It depends on whether the pressure is low or high.

Safety Valve (High Air Pressure) 

The governor is another component in an air brake that monitors the pressure. It will signal the compressor to cut off the pressure when it’s too high and vice versa. However, at times, its failure brings the safety valve into play. 

The safety valves are passageways connected to the tank. Their purpose is to direct the excessive air outside. It usually begins operating when the air pressure crosses 150psi or 1035kPa. 

Warning Device (Low Air Pressure)

Every vehicle with an air brake system has a low air-pressure warning device. It is present on the instrument panel and provides a visual warning. It will either flashlight or buzz loudly to inform you about low-pressure levels. 

Sometimes, the warning device may also ring an alarm or bell. The exact warning method depends on your vehicle. Nonetheless, these devices get stimulated when the pressure drops below 55psi or 60psi (380kPa to 414kPa).

Unlike a safety valve, the warning device will not regulate the lower pressure levels. It’s best to bring the car to an immediate safe stop. Otherwise, you may encounter an accident or injury.

What Are the Maximum Leakage Rates? 

The maximum leakage rate is less than 4psi in 1-minute for a single-vehicle. Meanwhile, the rate is less than 8psi in 1-minute for a combination vehicle. In case you’re wondering, here are the differences between both the vehicles:

  • A single-vehicle is any vehicle that is small, light, and does not have additional pieces trailing behind. Almost anyone can drive it easily. 
  • A combination vehicle refers to a tractor unit with one or more trailers attached behind. It is heavier, longer, and demands more driving expertise. You will usually find it on highways, in industrial areas, and the countryside. 

How to Check Maximum Air Leakage Rate

Checking the air leakage rate is a fairly simple process. First, make sure that the air system is in the normal operating range or you can say fully charged. Drive the car for some time to ensure that. 

Next, turn the engine off and release your grip on the parking brake. Record the time taken for the air pressure to drop using the gauge. In case the value is above the maximum leakage rate, contact a professional immediately to fix the issue.

Final Thoughts 

All in all, draining your air tank is a very important task. You should do it every day to avoid brake failure or tank corrosion.

Regular draining also helps maintain the air tank. A well-maintained air tank can last a long time, sometimes up to 10 to 15-years. So, if you want to keep your air tank in working condition and stay safe, make sure to drain it daily.