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Best Air Compressor Water Separators & Moisture Filters 2023

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Water separators are very useful components that are designed to remove contaminants from the compressed air as it leaves the air compressor before it arrives at your tools.

It’s a very odd thought to think about protecting your tools from the very thing that brings power and life to them, but the nature of air compressors makes them the biggest threat to tools well being and longevity.

If you use compressed air, even if only to inflate your tires, you should have a water separator installed on your compressed air system. Most people don’t realize how destructive water can be to tools and even to tires. Water can cause rust or deterioration tools and tires, shortening their life.

This article will provide you with a greater understanding of water separators, and provide some of the best providers/products.

Table of Contents

What is an Air Compressor Water Separator?

Air compressor water separators are designed to remove contaminants from the compressed air as they leave the air compressors on their path to your tools. The contaminants can include the following:

  • Liquid water
  • Water vapor
  • Solid particles
  • Oil
  • Oil vapor

Compressing air creates a problem with water as all air contains water vapor. When you compress air, the water vapor is forced out, and it must collect somewhere within your air compressor. The logical place for it is in the air tank, hence why air compressor manufacturers put drain valves at the bottom of the air tank.

During operations, the pressure in your air tank varies up and down as it streams air down the connection to your tools. This air picks up water vapor and ends up taking it to your tools too. Water in the cylinders of these air tools can cause some serious damage, even when being careful.

It is therefore imperative to think about protecting your tools by removing the water or other contaminants from the compressed air before it reaches your tools.

This is why you need an air compressor water separator. They will protect your tools from rusting as well as keeping the performance up to scratch.

How do Water Separators Work?

A water separator is simply a small addition that is attached to your air compressor to remove all liquid water, water vapor, solid particles, oil, and oil vapor from reaching your tools. As it removed all of these contaminants from the compressed air, it allows for clean and dry air to be delivered to your tools. Resulting in efficient and optimum performance.

There tend to be two different methods by which compressed water separators remove contaminants from the compressed air in your system… both are very effective at providing you with a clean compressed air supply.

Centrifugal Separators

Centrifugal separators are designed with a rotary or spinning motion. This motion compresses the air as it passes through their separators, causing the contaminants to speed up.

As the particles, oil, or water speed up, they’re forced to the outer edge and collect on the inside of the separator housing. Here, they move to the bottom of the housing and can then be drained.

This draining of the centrifugal air separator can be done manually and also even automatically if an automatic drain system is installed into the separator.

Coalescing Separators

Coalescing separators utilize a filter element. This filter element traps the varying contaminants in your compressed air supply as they move through the filter.

Compressed air is forced through a filter medium from the inside of the air filter to the outside. The compressed air then exits the separator at the outside. It is recommended that these air filter elements be replaced regularly.

The Best Water Separators & Filters For Your Air Compressor – Our Picks

LE LEMATEC Air Compressor Filter Oil Water Separator

If you’re looking for something to cover your occasional use of your compressed air system, then it is recommended to buy an air separator that is the most cost-efficient.

If you only use one tool and do so occasionally, or you’re looking to put air into your car tires, then an inline water separator is probably your best choice.

This Le Lematec inline separator is convenient to use and provides a great solution to providing clean air into your air tools at a reduced cost. This separator can be mounted to your tool or the end of your air hose and boasts some great features for its price:

  • All brass fittings and metal housing
  • Comes with a money-back guarantee (not all do)
  • The convenient push-button drain system
  • Replaceable filter element
  • Shock-proof and very durable
  • Traps water, oil, and dirt particles


  • Cheap enough to mount one on each of your air tools
  • Simple, very easy to use, and install
  • Small size, making it handy in spaces with limited room
  • The push-button drain system is clever


  • Airflow can be restricted which will cause operation problems
  • Due to its small size, it fills up with water or other contaminates very quickly

THB 1/2″ Heavy Duty Particulate Filter and Moisture Trap

It can be a very difficult challenge to find an automatic draining system on a water separator for a reasonable price. The majority of low or mid-range compressed air water separators suitable for home or hobby use are simply too expensive.

That’s where the THB 1/2″ heavy-duty particulate filter and moisture trap comes into play. This may just suit all your needs. It is a very well-built and durable water separator that comes with an automatic draining system at a very reasonable price. Its features include:

  • Heavy-duty construction for long life and great durability
  • Internal float drain
  • Maximum out the pressure of 215psi
  • Maximum input pressure of 250psi
  • Sight glass on the bowl
  • 140cfm flow rate
  • 1/2″ female NPT fittings


  • An automatic draining system is great
  • Easy installation
  • Very well constructed
  • Works very efficiently


  • The float value sometimes sticks and doesn’t drain

Neiko 30252A Water and Oil Separator for Air Line

The Neiko 3025A water and oil separator is suitable for using inline and is very easy to install and use. It includes a 1/4″ NPT fitting that tightly fits into couplers without any leakage.

A simple product like this can extend your tool life by preventing the air tools from breaking down and protecting the inevitable water and other particles from entering.

It boasts a simple valve press that allows you to release and eject waste in a flash with minimal cleaning.

Some of its features include:

  • Universal 1/4″ NPT inlet and outlet design
  • Maximum operating air pressure is 90 PSI
  • Stops water vapor and particle from entering pneumatic tools
  • Rust-proof aluminium housing and brass fittings


  • Lightweight
  • Easy to use
  • Reliable filtering
  • Secure fit


  • No flow indication
  • Difficult to dry out

Air Compressor Water Separator Buyer’s Guide

When plumbing an air compressor, probably the most important consideration is the drain type. A drain is a very essential part of a water separator. It works by removing the excess water and helps you to keep your pneumatic tools working efficiently for a longer duration.

There are 3 different types of drains available on the market currently.

  • Manual: drains require you to check their moisture level and drain it by yourself when required
  • Semi-automatic: drains excrete when there’s no pressure and close while the airflow is passing by
  • Automatic: drains usually drain themselves when the water level on the bowl is ½ way full. At this point, the float gets displaced and lets some moisture out of its system

The bowl is one of the main components of the filter component and must be able to withstand lots of pressure. It is therefore very important that you get a bowl that is of good quality and can last for a long duration.

All loads of your air compressor fall onto your water separator. Even the best water separator for air compressors will be useless if it cannot cope up with the air compressor load, making this an important consideration.

A final consideration is material, if the material is made of glass, then you can check the moisture content inside it through the glass display and know when it’s the right time to drain the water completely.

FAQs (Frequently Asked Questions)

Where does the Water in My Compressor Tank Come From?

As the air compressor pump compresses the air, it heats up. As the compressed air is used, it cools and any water vapor that was in the tank is heated and condenses on the inside of your air tank, collecting at the bottom.
This collection of water will eventually corrode the tank and be carried down the air hose into your tools, causing them to rust and potentially have serious issues.

Where to Install Water Separator on Air Compressor?

Air compressor water separators are usually installed in-line after the air has been compressed and left the air receiver tank on its way to your pneumatic device.

If you have a regulator to reduce the pressure at a specific drop towards the end of your line. The water separator will come after the regulator as the regulator cannot be harmed by moisture.

Another reason being due to the pressure drop across the regulator, more air will be cooled and thus the water separator will be able to capture a greater amount of water and provide your pneumatic tool with a greater quality of air!

Do I need to Change the Filter?

Yes, it is important to change the filter after a certain period. This is hard to give an exact time period as it primarily depends on your usage and the humidity of the space.
If you witness any leakage or distortion of any sort, this is also an inclination to change the filter.

Keeping Things Dry

At the end of the day, the most important factor to consider is protecting your investments in the tools and other uses of your compressed air. The goal is to stop the water, oil, or particles from migrating down the system and into your tools.

No matter where you are or what you are using your air compressor floor, from domestic uses to factory uses, it is in your best interest to have a water separator installed on your compressed air system.
Hopefully, this page has provided you with answers to most of your questions surrounding air separators, and you can now make a confident decision on installing one.

Further water prevention methods

Another method to help prevent water from passing through the system is to drain the compressor tank, view this page for a detailed hot to process.

Further Reading

How to clean the insides of air compressor tanks

Best Quiet Air Compressors

If you have any questions regarding water separators, please leave a comment below, with a photo if applicable, so that someone can help you!

By Bill Wade

About Air Compressors has been helping folks with their Air Compressor Problems since 2002 online. We're a community of DIY and Compressed Air professionals who are keen to support everyone across the globe with their air compressor issues and troubleshooting. Whether you're trying to identify an old air compressor, or troubleshoot an error code on a sophisticated new industrial air compressor - the community at About-Air-Compressors.com is here to help you

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