The Best Water Separator for Air Compressor

If you have air tools then getting water inside of them can be a nightmare. This can often happen when condensation forms in your tank and feeds through the line.

Water can cause malfunctions, rust and poor results. The solution is to get the best water separator for air compressor.

What makes the best water separator?

We looked closely at the overall build quality, the drainage system, size, types of filters and other key factors such as operating pressure and load capacity. If that sounds a little confusing then we’ll go through everything in our buying guide.

To find the best water separator for air compressor we’ve found the top 4 models out there today and completed an in-depth review on each of them. We’ve also got that buying guide along with some FAQs to give you all the info you need.

Let’s get started!

Our Pick

Campbell Hausfeld water separator

Campbell Hausfeld NPT 3/8” Air Filter

It’s able to give you this high-quality filtration while still providing a 57 SCFM flow capacity at a PSI of 90. Whether you’re using an impact wrench, grinder, air hammer or anything else, this separator will allow you to use it with confidence.

This Campbell Hausfeld model is our top pick for many different reasons. It’s excellent at being able to protect equipment and prevent contaminants from entering your line. Along with water, it will prevent any ingress of oil, dirt, or dust.

That’s all aided by the 5-micron filter that is included within the separator. That will prevent any fine particles from getting through but there are plenty of other impressive features here. One of those is the quick-release bowl that makes removal and monitoring of the liquid level very easy.

Also included is a quarter-turn drain that makes maintenance incredibly simple. It will help to ensure that only the cleanest air is getting into your equipment with the oil removal filter and the desiccant system that removes aerosols and vapors.

What we like:

What we liked the most here was simply the results. All water vapor is going to be blocked, as will any oil. It’s highly effective at doing its job and it will produce better results with your tools while also extending their lifespan.

Installation is also very simple with this device and it should only take a matter of minutes. When you have it installed, it will give you a perfect fit and it will work without any issues. That’s a testament to the high level of build quality throughout.

The steel body of the separator shows the level of materials used, which should ensure that this model lasts for years to come. It’s very easy to use and will do all of the hard work for you. It’s very highly rated by its users and it’s easy to see why.

What we don’t

While most of the materials used are high-quality, the see-through bowl is made from plastic which may not have the same level of durability, the same goes for the drain. They do seem to be quite tough so hopefully, there won’t be any issues.

How we chose the best water separator for air compressor

There are many different aspects to look at when it comes to getting the best water separator for air compressor. The first thing we checked was simply performance.

Was the separator effective enough at ensuring no water gets into your tools? All 4 models here passed that test.

Following that, we looked at how well they were made with factors such as the quality of the bowl, how good the drainage system was, which materials were used and what pressures it could cope with. It had to pass those tests in relation to long-term durability.

Compatibility was also important and then there are other considerations such as the overall size, capacity, what type of filter it has and the ambient temperatures it operates at.

We took all of this into account to come up with four models that are all a little different but all have exceptional quality.

Best water separator for air compressor

NANPU 3/8″ NPT Compressed Air Filter

NANPU NPT Compressed Air Filter

The filter is highly adept at being able to get rid of any water or solids that may be in the system.

If you wanted to have a little more functionality from your water separator then this is going to be ideal. It’s highly effective at being a filter, regulator, and lubricator. All of this comes at a very good price and one that is well worth paying.

In addition to the filter is a regulator that will adjust the outlet pressure along with a lubricator that can add oil to your tools when required.

There is a good level of flexibility here as you can add an extra outlet if you needed. While it has that flexibility, it also has incredible durability to ensure that it lasts for a long time. The level of construction is impressive.

A wide range of buying options are available here as it comes in sizes of 1/2″, 1/4″, 3/4″ and 3/8″. Hopefully, that allows everyone to get the separator they need. Added to that, it’s a user-friendly device and you’ll have it up and running in no time at all.

What we like:

As with our top pick, this also comes with a 5-micron filter. That’s a highly effective size that will catch all but the very smallest of particles. It allows the tool to have a consistent and excellent performance at all times.

The model that we looked at came with a semi-automatic drain. This easily removes excess water when required. NANPU also made a fully automatic drain but that is only available within the 1/2″ and the 1/4″ sizes.

We also appreciated the number of accessories you get here such as the seal tape, plug kit and air coupler. Installation is also straightforward and you’ll have no complaints when using it. It does the job extremely well and is very well made.

What we don’t

We had very few complaints about this water separator. A few users have reported a few leaking issues but this appears to be a very rare issue. While it was quite easy to install, this wasn’t helped by a lack of instructions which may be frustrating for some.

THB 1/2″ Particulate Filter Water Trap Separator

THB Particulate Filter Water Trap Separator

The semi-automatic drain works very well and makes the separator very easy to use.

THB is another company that has made a very highly rated water separator with a long list of happy users. It’s a very good model and one that comes in three different size options of 1/2”, 1/4” and 3/8” so hopefully you can find the perfect fit.

The materials used are a high-quality mix of plastic and metal that offer a high level of build quality. It makes it an ideal separator for those that need one for everyday use. It can take a lot of punishment and keep up its high level of performance.

Perhaps the most unique feature of this separator is the drain. It has a semi-automatic operation where it will hold the water if there is pressure on top of the bowl. After that pressure is released, the water will then discharge without you needing to do anything.

It has a fairly large 5oz bowl that is solidly built and a filter that will get rid of almost all debris. It does this while maintaining an exceptional CFM of 106. That’s along with pressures of 145 and 175 PSI for the output and input respectively.

What we like:

The first thing we noticed about the separator is that it comes at a great price and offers excellent value for money. This is also helped by the internal filters being affordable, easy to obtain and also easy to replace to reduce ongoing maintenance and cost.

The usability is also aided by how easy the water separator is to install. Operation is also fairly simple so you’ll be able to use it without any frustrations.

As with any of these models, they will be ultimately judged on their effectiveness. It’s where this is able to excel as it will prevent any moisture vapor from getting into your air tools. It combines that performance with high-quality materials to make a brilliant water separator.

What we don’t

While the overall quality is quite good, we do have questions about the quality of the plastic bowl. It may leak after heavy use which is something to keep an eye on. Most people, however, are very happy with the long-term durability of the separator.

LE LEMATEC Air Compressor Filter Oil Water Separator

LE LEMATEC Air Filter Oil Water Separator

With this separator, you also won’t have to worry about ongoing maintenance costs. That’s because the filter is washable and doesn’t need to be replaced.

This may be the smallest water separator that we’ve looked at but it is still very impressive in its performance level. It’s a versatile tool that will allow you to separate any type of debris that may otherwise get into your air tools.

It’s exceptionally easy to use as you can connect it and disconnect it with ease. It makes it a great option if you have a range of different air tools for various applications. Not only is installation simple but this separator is also easy to clean.

As soon as you get it into your hands you’ll feel the level of quality that it has. It’s very well built with the highest levels of durability and construction. That’s due to it being made from a high-grade aluminum that allows it to be shockproof and excel in a wide range of temperatures.

The drain value works via a push button and works very well. You’ll easily be able to discharge any moisture and keep using your air tools. It’s the ideal water separator for anyone looking for something a little lighter and more portable.

What we like:

We loved the versatility of this filter which is aided by the high level of compatibility. Along with water, it will easily be able to clear any oil or dirt. All of this comes at an exceptional price and a lot more affordable than some other types of water separators.

The unit is also lighter than almost all other separators but as we mentioned previously, it has a high level of build quality. Along with that aluminum casing are brass fixtures that give you ultimate durability. It allows the separator to take plenty of punishment time and time again.

It’s a cost-effective option and one that will work in any position with a wide range of tools.

What we don’t

The biggest downside to its size is that it doesn’t quite have the same capacity as some of its rivals and therefore may not be suitable for all professional uses. It also doesn’t quite have the same level of airflow capability as some of its rivals either.

Why you should get a water separator

If you’re using any air tools then you need to stop any water or other contaminants from getting to them. That’s why you’ll always want something that can filter out the air and there are a few key reasons for that.

They generally fall into two categories of durability and performance. In terms of durability, water ingress into your tools can quickly cause rust and other issues. With performance, any interruption in airflow can cause issues in the operation of a tool.

If you want your tools to last for as long as possible then a water separator is a must. It may add an extra expense to your system but, in truth, that is going to be minimal, especially in comparison to the cost of a brand new air tool.

The good:

  • Expends life of tools
  • Prevents rust
  • Allows consistent airflow
  • Provides better results

The bad:

  • Extra expense

Key features of a water separator for air compressor


You’ll want to get a water separator that matches the jobs you need to complete. The Campbell Hausfeld Air Filter is a good example of a medium-sized separator that may need to be fixed into place and is a little heavy to carry loose on the line.

The NANPU Compressed Air Filter is a little bigger and comes with fixtures included that allow you to attach it to the wall. The reason for that is it partly being a combination filter that also has a lubricator included. This makes the unit heavier.

For handheld operations, such as that with a paint gun, the LE LEMATEC Air Compressor Filter would be ideal. This can be installed just behind your tool and won’t cause much additional strain on your arm. It’s important to get the right model for the jobs and tools that you have.

Bowl quality

The bowl is where the contaminants are going to collect once they have been filtered out of the airline. These need to be made from high-quality materials as otherwise, they can crack quite easily. They are also hard to replace so you’ll want to ensure that it can live with the pressures.

A few different materials can be used with the bowl. Metal can be used but it doesn’t have the benefit of being see-through. That’s why polycarbonate or toughened glass is often used as it can be very tough but also transparent so you can see into the bowl.

This is the design that you will often see. This see-through bow, however, will have a metal guard around it that will work to prevent any impacts or damage. Many see this as the best compromise of materials and usability.

Drainage system

Once you’ve stopped that water from getting into your air tools then you need to get rid of it.

This will be the drainage system which is almost always situated at the bottom of the bowl as it will give you the easiest method of removal.

There are different types of drainage systems as they can be manual, semi-automatic or fully automatic.

Manual – This is a system that you’ll need to work yourself when the water level starts getting high. With this type of drain, you must remember to empty your tank regularly. This should be after every use (or daily) or at the most, once per week.

Semi-automatic – These work very well for a lot of people and take the hassle out of draining your system. They will usually empty when there is no pressure. The drain will then automatically close up once the pressure increases.

Automatic – With this type of drain, it will automatically drain once the water passes a certain point. This is usually when the bowl is around 50% full. Once that threshold occurs, a float will be released and the water will drain out of the system.

Build quality

The overall build quality is important as any parts of an air compression system are going to be placed under plenty of stress.

It’s also important to minimize any chance of corrosion. Most separators are a mixture of metal and plastic but it depends on what type of plastic and metal are used.

Polycarbonate is often used for the bowl as it is very strong. A lot of the drains, however, will be made from weaker plastic but this is less important as they are on the outside of the separator and don’t need to cope with the pressures.

With the rest of the separator, stainless steel is often used to protect against corrosion. Even better than this can be aluminum which has is less prone to rust.

This can be mixed in with brass fittings to combine the best of all words for low weight, maximum strength and minimum corrosion.


This isn’t included in all types of systems but can be useful when you’re dealing with higher pressures. It will show you the pressure level running through the system.

This can be useful if there has been a pressure drop or if your separator is getting close to its maximum operating loads.

Types of filters

There are many different types of filters available. You may need some in different circumstances but most standard models will have a simple water separator filter which we will look at first.

Water separator filter – These basic filters will be used when you’re only worrying about water getting into your air supply and no other contaminants. That being said, most of them can also filter out dirt and oil.

Particulate filters – These filters are able to remove small particles from the system. This is usually after they’ve come through some sort of absorption dryer. They usually can capture very small contaminants, including corrosion particles. 

Activated carbon filter – Activated carbon is found in many types of filters as it’s exceptional at being able to remove many different types of contaminants, partly due to their huge surface area. For compressed air, they are very good at removing oil vapor and odors.

Coalescing filters – There are used to remove aerosols from the air. They trap smaller droplets which then turn into bigger droplets that are then removed and prevented from getting back into the air. They are great at getting rid of oil and water but need to be changed regularly. There are cold versions of these filters which increases their efficiency.

Compressed intake filters – If you want to get rid of airborne contaminants then this filter is great at being able to block particles. You’ll mind that many will trap anything that is larger than 0.5 microns in size but some of them can be even more efficient than that.

High-efficiency filters– As the name suggests, these filters are incredibly efficient at removing particles from the air. These are for the highest end of quality with some being able to trap particles of 0.01 microns. They can do this without having any pressure drop.

Flow rate

You need to have a flow rate that is capable of coping with your compression system. This is usually rated in CFM which stands for cubic feet per minute.

This is usually correlated with the PSI figure but they are separate figures so you’ll want to check the compatibility of both.

Operating pressure and load capacity

You’ll also need to know that the minimum and maximum operating pressures of your water separator are. This is rated in terms of pounds per square inch (PSI) of pressure. You should already know the air pressure capability of your air compressor.

If you get a separator below this input level then you’ll need to reduce the power of your compressor.

Due to this, you’ll want to choose a separator that can cope with whatever your compressor can throw at it. Most separators can cope with high pressures but it’s important to check.

The pressure output is going to be vital too. There will be some drop in pressure as it goes through the separator. You need to ensure that the air coming out of the other side is still strong enough to power your tools.

Ambient temperature

Ambient temperature may also be another consideration of your device. This will look at the water separator’s ability to deal with particularly high or low temperatures.

This isn’t usually going to be an issue but may be worth checking if working in a hot or cold environment.


How do water separators work?

Wondering how do compressed air water separators work? Well, separators work via two main methods. Both work very well so it’s not going to be a huge factor in your buying decision but it’s good to know how they work.

Centrifugal separators – These separators uses a spinning motion to throw any water vapor to the outside of the bowl. The spinning motion will increase the speed any contaminates will be directed away from the airflow. This can then be drained away with either a manual drain or an automatic one.

Coalescing separators – These separators will simply use a filter to trap any water along with anything else that may be in the air supply. These are common as the air will be passed through the filter and clean air will come out of the other side. These filters often need to be replaced but some of them are washable.

How to install water separator on the air compressor

Installing your water separator is a fairly simple process and shouldn’t take too long.

The first thing to note is that you need enough airline running from your compressor so that the air can be cooled sufficiently before it gets to the separator. Without this, your separator isn’t going to work effectively. Around 50ft of airline is suggested.

You will then probably need to mount larger units with something like an L-bracket. This will allow it to cope with the pressures that run through it. Other smaller units can be attached straight from the line and it’s important to follow the manufacturer’s instructions.

All you need to do now is connect your inlet and outlet pipes. It’s a good idea to use Teflon tape on the fittings to ensure that you have an airtight seal. Once you have it all connected then you’ll be ready to go.

Does my air compressor need a water separator?

Air compressors work by sucking in a large volume of air and then storing it into a pressurized tank. The problem with this air is that it contains a large amount of water vapor and also other containments that may be in the air such as dust.

Some of this water will accumulate at the bottom of your tank while some will stay as water vapor.

Even if you drain your tank after each use, you can still get water vapor in the line. This is why it’s always a good idea to have a water separator when you’re using an air compressor.

How to keep water out of air compressor lines?

Unless your air compressor can intake air from a magical source without any humidity then you are going to get water in your air compressor lines.

Some air compressors will try and deal with it beforehand with pre-filters and air dryers but these will never be 100% effective.

There is a reason why all air compressors come with a drain and that’s because they know they’ll need to be emptied. It’s therefore important to focus on any moisture from not reaching your air tools. A water separator is the best way to do this and the high-quality models are highly effective.

Why does my air compressor make so much water?

It may not seem like it at times but there is water all around us at all times. There are said to be 37.5 billion gallons of water in the atmosphere. We release plenty when we breathe and this can always be seen on a cold surface in the form of condensation.

Even when the air seems relatively dry, there will still be plenty of water in it. This makes it inevitable that an air compressor is going to make so much water, included in that air can be other pollutants that can be caught up in your air compressor.

Why is moisture removed from compressed air?

Air tools simply aren’t built for water running through them as water still start to rust the interior of the air tools and ultimately lead to their deterioration and then failure. This can lead to the very expensive replacement of tools.

This is not only in terms of rust but the water can also wash away any lubricant and cause the rapid acceleration of any wear. If the water is slightly acidic it would also start wearing away at the pistons, valves and motors within.

While this damage is bad enough, it can also cause a drop in performance. It can cause inconsistencies in the air line but if you have something like a paint gun, then that water will come straight through the tool. This can cause problems with the paints and affect the finish.

These are the reasons that water is removed from the compressed air. The small price that you pay for a water separator can lead to big savings on tools. This is why you want to remove as much air as you possibly can.

How often should you change desiccant?

When you need to change desiccant will depend on a few key factors. It’s generally only found on the larger capacity air compression systems that are either used for professional or commercial use. Some smaller separators will also use a desiccant.

Some desiccants can regenerate and have the water removed. For most people, two to three years is a good timescale to remove that desiccant. This will ensure that it remains at the top level of performance and keeps that air as dry as possible.

Why drain water from compressed air tanks?

As water is heavier than air, any water trapped inside the tank is going to fall into the bottom. This water will eventually build up until the tank would eventually become filled with water. This would take a long time but that water can cause other issues.

If it’s sitting into your tank then there is more chance of it evaporating and becoming water vapor which would then get into your air lines.

Due to this reason, it’s best to drain the water from the tank after use to keep any moisture as low as possible. Even though your water separator will take out any excess water, you don’t want to make it work too hard.

How to prevent water in air compressor?

It always a good idea to have a water separator regardless but it can also be a good idea to try and remove as much water as you can in other parts of the system.

You can do that in a few different ways which we’ll explore here. This will depend on how big your air compressor is as they don’t all have the same functionality.

Refrigerated air dryer – Refrigerated air dryers are effective as cold air holds a lot less moisture than warmer air. The refrigeration of these machines will cool the air down to as little as 33F. Any excess water vapor in the air will condense and turn back into liquid water. This will then fall into a water trap and then be removed via a valve. This air will then be fed back through the production lines at room temperature with a lot less air.

Desiccant air dryer – These types of dryers are only really required when you need the absolute driest of air. Desiccant is a type of material that will chemically respond to the liquid to form a bond. Different desiccant air dryers will use different materials such as a molecular sieve or activated alumina. The compressed air will be passed through a tower containing the material and it will remove almost all of the water and ensure it has an incredibly low dew point. These systems lack a bit of efficiency as they consume energy and there will also be some air loss. They are, however, ideal for anyone who needs the driest air.

How to remove water from air compressor tank?

As we mentioned there, cold air contains less water vapor than hot air. As the air that comes from the pump is going to be quite hot, it’s going to contain plenty of water vapor.

When it reaches the tank, it will cool and condense. This water will eventually make its way to the bottom of the tank. You need to ensure that this water is drained from your tank on a regular basis.

You’ll firstly want there to be a little pressure left in the tank as this is going to help blow any water out. You’ll want to ensure that the pump is turned off and then you can open up the drain tap. Once all of the water has been removed, you can then close the tap back up.

Some tanks will have a manual drain whereas others may have an automatic tap which removes the need to remember to empty it. This can be a useful feature but in reality, draining the tank is usually a quick and easy job and will prevent any build-up of water.

How to clean air compressor water separator?

Over time, the filter is going to get clogged up and will either need to be cleaned or replaced.

How and when to do this will depend on the manufacturer but it’s usually a fairly simple process of unscrewing the separator and replacing the filter.

How much CFM do I need air compressor water separator?

The answer to this question will depend on what type of system and tools you have. A large compressor and more powerful tools will need higher pressures and a higher CFM.

If you have a small compressor tank and less powerful tools then the needs are going to be fewer. It’s a good idea to check your tools and tank, and then get a separator that can match that.


Hopefully, now you’re armed with all the information that you need to get the best water separator for air compressor. You should be able to choose the best water separator for you depending on your needs and the tools you have.

While we loved all four separators we looked at, our top pick would have to be the Campbell Hausfeld NPT Air Filter. Its performance was unbeatable and has a great level of build quality.

Hot on its tail was the THB Water Trap Separator which has many of the same qualities. Both are brilliant at extending the life of your tools.

For anyone looking for a bit more capability, the NANPU NPT Compressed Air Filter would be excellent with their dual system. It offered great value for money and we were particularly impressed by the semi-automatic drain.

Looking for something a little lighter and more portable? If so then the LE LEMATEC Water Separator would be your best bet. It may be small but it offers you exceptional quality throughout and is able to produce excellent results.

In truth, any of the four separators that we’ve looked at here could have won our top pick. They are all brilliant in their own way and one may be more suited to your needs than another. If you aren’t sure, then simply look over our buying guide once again. All you need to do now is to choose your favorite separator and enjoy all the benefits it provides.