Air Compressor Oil Water Separators

What is an Oil / Water Separator?

Oil / Water Separators (also known as simply a water separator, water trap or a condensate separator) are mechanical separators that are typically installed behind the air compressor tanks. They have the appearance of an in-line air filter and such an internal separator separates water from oil by spiraling the air using centrifugal force, which pushes the oil out. An internal oil-water separator will be found within your air compressor. This oil is used to lubricate the rotary screw and other internal components. You’ll also want to utilize an external oil-water separator in addition to this internal component.

I won’t go into depth on the compression process and how compressing air generates water, except to say that the more air you compress, the more water you’ll have in your compressor tank or in your air network.

Water may have a variety of negative consequences on the air compressor and the equipment linked to it; air tools are particularly vulnerable to moisture and dust-laden unfiltered air. Your air compressor’s water separator or filter-drier is responsible for removing all liquid water, steam, solid particles, oil, and oil vapors. As a result, the water separator improves the efficiency of your pneumatic equipment while also ensuring job precision.

For a lot more detail on air compressor oil, see our full guide What Is Air Compressor Oil?

How Does an Oil Water Separator Work?

An air compressor oil-water separator is straightforward, requiring only a single manifold connection between it and condensate sources. Water is often collected in the following components as a result of air compression activities:

  • Receiver tanks
  • Air filters
  • Air drying systems
  • Condensation traps

The filtering process can begin when the water has been directed from various sources to the separator.

The water tray is automatically divided if there is no air pressure in the system, while the drainage column rises when the air pressure is turned on. Because water vapor in compressed air can condense anywhere along its flow route during the compression process, a compressed air filter should be put in front of any air-carrying equipment or pneumatic tool to remove any water that condenses in the lines between the source and the pneumatic tool. Automatic drains empty the filter tray on a regular basis. Otherwise, to prevent water and crude oil from being forced back into the airflow, the trays must be manually emptied on a regular basis.

When air is pulled into your air compressor, it compresses at a pressure twelve times that of normal atmospheric pressure. However, this filter isn’t always adequate to cure all of your water concerns while utilizing your compressed air equipment. When you pushed the trigger on your air hose, you must have seen water come from the pressure hose. You must monitor water levels on a frequent basis to keep an eye on them, which necessitates easy access to your gadget.

The compressed air is passed via a tiny hole and utilised in a number of ways when the air in the chamber reaches the top limit. Furthermore, such a powerful tool may assist preserve the compressor’s interior parts from rusting and its performance up to date. It features a single cylindrical body with a nut on top to connect to the air compressor and an aperture at the bottom to drain the accumulated water. It does not come with regulators or meters.

air oil separator

Oil Water Separator Tips

  • It’s not a good idea to use an air compressor without a water oil separator due to the damage the water can cause.
  • After 1,000 hours of use, you should replace the air compressor moisture separator if you want your compressor to function at its optimum.
  • These water separators may remove 40-60% of the water from compressed air depending on the temperature of the compressed air.
  • The load capacity of the filter is determined by its operating pressure. In comparison to a 100 PSI product, an air line water separator with a maximum working pressure of 150 PSI has a higher pressure capability. Clean and dry air is provided to your tools instead of unfiltered air since it eliminates all forms of impurities from compressed air.
  • Air compressors come in a variety of shapes and sizes, so you’ll need to buy a separate air filter and water separator for each one. You should read your instruction manual thoroughly to choose the best air compressor water separator for your particular compressor.

Components of an Oil Water Separator

The following are the key components of an industrial oil-water separation unit:

  • Connection channel
  • Cyclonic depressurization chamber
  • Filter cartridges
  • Exit drain unit
  • Activated carbon system

Here’s a great video I found on YouTube about Oil / Water Separators on air compressors. Credit DIY ALAM.


How to Install Oil Water Separator on Air Compressor

*WARNING* Before you begin, make sure the main power switch is turned off.

Once that’s done, you can begin the installation process:

  1. First wrap some teflon thread tape around the quick connections so that the coupler and the 90-degree elbow  are air tight.
  2. Then, in the 90-degree elbows inlet hole, screw out the coupler (male plug connection) and connect it using your fingers. Then tighten it even further using a wrench.
  3. After that, fasten the separators‘ inlet hole to the outlet hole of the 90-degree elbows. Don’t forget to use Teflon tape again here to seal it. If tightening with your hands is difficult, a wrench may be used.
  4. Using the same procedure, insert another 90-degree elbow into the outflow hole of the separator. Seal again with teflon tape.
  5. Then, remove the air compressor’s hose tube and connect the oil water separator to it. Once again, use a wrench to tighten it properly.
  6. Finally, connect the oil/water separator to the air receiver tanks’ input connection, which you disconnected the hose from before.

That’s it – you’re ready to use your new oil water separator 🙂

How to Build a Homemade Air Compressor Water Separator

So, how to make a DIY water trap for an air compressor at home. Your first line of defense against moisture in your air compressor is to properly use the filters that come with your equipment. Combining two or more of these methods is an even safer way to keep your compressed air system dry. And you’ll need to install your homemade air water separator directly between the hose line connection and your pressure tank.

Equipment & Parts List

Here is a list of everything you’ll need to have at hand before beginning and their quantity in brackets (if applicable):

  • Teflon tape
  • Soldering flux
  • Solder
  • Propane torch
  • 3/4″ Brass street elbow with male & female ends (1)
  • 3/4″ 90 degree Copper Elbow (10)
  • 3/4″ Copper pipe in 2″ lengths (9)
  • 3/4″ Copper pipes (Type L) cut in 72″ height (6)
  • 1/2″ Threaded ball valves with female ends both sides (3)
  • 3/4″ Threaded brass ball valve with female ends both sides (1)
  • 3/4″ 1/2″ male adapters (3)
  • 3/4″ Copper Tee (3)
  • 2 1/2″ to 3/4″ Brass nipple (1)
  • 3/4″ Threaded male adapter (1)
  • 3/4″ Brass compression fitting for regulator (1)
  • 3/4″ Rapid air NPT filter regulator (1)
  • 3/4″ Threaded brass ball valve with female ends both sides (1)
  • 3/4″ Compressed air hose (1)

DIY Water Trap for Air Compressor – Step-by-Step Guide

Let’s get started on making a homemade air compressor water separator now that you have everything you need!

  1. To begin, link three x 2′′ copper pipes together on each side using a 90-degree copper elbow. To prevent the pipe from being oxidized when heated, add a small amount of soldering flux inside the copper elbow and on the exterior of the pipe before connecting them together.
  2. Fix a copper tee on each of the remaining 3 x 2′′ copper pipes, then add the remaining copper elbows to the ends of each copper pipe. Make sure you reapply soldering flux.
  3. Take the junction with the copper tee and link each pipe with the remaining 3 x 2′′ copper pipes. The copper tee should be linked to the second 2′′ copper pipe.
  4. Connect the junction with the copper tee to two type L copper pipes using five copper pipes. One of your joints should only be connected to a single long pipe, so make sure that the side with the copper elbow is connected.
  5. Attach the other couplings to the opposite side of the type L copper pipes, ensuring that the air movement through the chambers is uninterrupted. A single pipe will connect one of the junctions.
  6. To guarantee that the pipes do not leak, use the propane torch and solder to solder the connections. To do so, heat the pipes at the joints and then melt the solder on top when they’re hot enough or the side flame becomes green.
  7. To eliminate leaks, connect the three male adapters (3/4′′ – 1/2′′) to each of the outlets at the bottom.
  8. Using teflon tape, secure the threaded 1/2′′ ball valves underneath the male adapters.
  9. Cut the remaining 72′′ copper pipe in half and secure one half on either side of the setup.
  10. The brass street elbow on one side connects to your regulator, while the pressurized air line from your air compressor connects to the other side.

You should now have a homemade water trap for your air compressor!

As mentioned above, you can get a lot more information on air compressor oil from our full guide What Is Air Compressor Oil?

Other interesting articles in the oil series are:



Jeff Stelling

Jeff Stelling is an air compressor obsessive who has been working with compressors for over 25 years, since he was an apprentice engineer in the mid 90’s. He designed to offer technical guidance and buying advice for compressors.