Condensate Drain Traps

Why are condensate drain traps important? The purpose of the condensate drain traps is to remove condensate from the compressed air stream.

Definition of condensate: The liquid formed from water vapor in the air and lubricant aerosol carried over from lubricated compressors, and which results from a drop in temperature and/or an increase in pressure.

When the compressed air exists the airend the temperature will be between 190F to 210F depending on the condition of the lubricant. The hotter the compressed air the more the moisture will stay in vapor form. From there the compressed air will then enter the aftercooler to be cooled down. By cooling, the vapor will turn into liquid and be able to be removed from the compressed air. It will exit the after cooler at a reduced temperature which is based on the size of the after cooler, condition of the after cooler and ambient conditions. The goal is to deliver 100F or less compressed air to the dryer. That being said, for every 20F the temperature of the compressed air is reduced the amount of moisture in the air is reduced by 50%. The condensate trap after the aftercooler will remove over 75% of the total amount of moisture in the air stream. The most important drain in your compressed air system.

In factories, compressed air must be kept free of moisture at all times throughout the manufacturing process. With moisture downstream various equipment will not perform efficiently and eventually breakdown. When a drain fails to eject the condensate collected, oil and/or water will collect, affecting filter efficiency which causes carry over into the system and allowing freeze-up in the winter. On multiple stage compressors moisture carry over from the intercooler may allow liquid into the next stage causing premature wear and possibly a catastrophic failure. On your refrigerated dryer the temperature indicator may still read 38F, but if your drain has failed, you’ll have plenty of water downstream. Slugs of water due to drain failure can cause major problems in a desiccant dryers as well. Drains stuck in the open position can be a major source of wasted energy caused by compressed air escaping through the drain port. All the above being said, there is a large amount of moisture in compressed air and it can cause major damage to your plant. Condensate drains are possibly the least glamorous and most ignored component of a compressed air system but nevertheless, a most important part. No matter how much you spend on that fancy new compressed air system, not spending a little effort with your drain choice could cause you endless headaches and increased operating costs for years to come.

Types of drains

Manual Ball Valve Drains

In some plants I have seen ball valves used. I have seen them cracked open, which bleeds dollars to atmosphere. A cracked open ball valve converts to approximately 20cfm. Based on $.07 KWh, this will approximately cost a facility over $2,000 a year. I have seen them used on tanks where it is left up to an individual to manually open once or twice a day. If any human error is made gallons of condensate can be pushed down stream causing havoc on all downstream equipment.

Pros: Lowest upfront cost
Cons: Most costly long-term cost

Timer Drain

These drains come with two settings, (how often) and (how long) to drain. Maintenance consists of pressing the “test” button to check its operation. Cleaning the inlet strainer is a must. A slightly different type of timer drain installed in larger systems is a motorized ball valve with timer. Timer operated drains should be considered a quick fix only. There are some issues which include not opening long enough to eject all the condensate or staying open too long wasting compressed air. The oil particles contained in the condensate can undergo change partly because of high velocities and direction changes, forming stable emulsions and causing problems with proper condensate separation and ejection. Because of this it is recommended to drain less more often. For a timer drain to be used efficiently, the drain times need to be adjusted to match the seasons, but just like the manual drain, we cannot rely on our operators taking care of this chore reliably and additionally we still have daily ambient conditions to contend with.

Energy wise this is cheaper than a cracked open ball valve. Example, a timer drain with 100psi at the inlet will move approximately 64.8 cfm. If this drain were open for 10 seconds and off for 3 minutes the average would be 3.6 cfm. Using $.07 per KWh, the approximate annual energy cost would be $448.00 per year.

Pros: Easy to install, cheap to purchase
Cons: It’s an engineered leak during non-peak high condensate time frames. Typically, the drain port is an 1/4”opening and can easily clog up without a strainer. Constant need to check on to assure proper operation.

Zero Air Loss Drain
IAC utilizes two types of zero air loss drains. Either of these drains will not have the annual cost associated with lost compressed air which is a cost avenue with the above drains. There are two technologies utilized. One is electrically powered and the is pneumatically operated.



The electronic zero loss drain IAC offers is manufactured by Beko. It utilizes a capacitance device to control the level of the condensate. There are two capacitive level sensors. One triggers the drain port to open and the other sensor will close the drain port. The location of the sensors is above the drain port which will allow no compressed air to escape. Over time to assure proper sensing it is recommended to replace the sensors once a year. This is a simple and important procedure.

Pros: Zero air loss, not overly expensive
Cons: Sensors need to be replaced annually, requires electrical power

Pneumatic Zero Air Loss Drain


The pneumatic zero air loss drain that IAC offers in manufactured by Drain-All. This drain uses magnets in its technology. There is a polymer float magnet that rises and lowers with the condensate level in the reservoir. There is inner magnet that seats up to an orifice that regulates control air that actuates a valve stem that opens and closes the drain port. The floating magnet uses the opposite magnetic pole to force the inner magnet to seat up against the orifice. As condensate raises the floating magnet to its highest position which is above the inner magnet in turn forces the inner magnet to unseat the orifice and allows control air to actuate the drain. Once the floating magnet lowers it will force the inner magnet to seat again. There are different models that are constructed to handle different issues. There are Drain-All models for high temperatures, pressures, old and rusty systems, etc.

Pros: Bullet proof, no electrical power required, standard ½” drain port, very low maintenance needed
Cons: Highest upfront investment