How to make a water separator for air compressors?

A visitor to my site used this search string “how to make a water separator for air compressors ” to find my compressed air information site earlier today. I find that usually if one person is looking, there are many seeking the same information, so, here is my response to that visitor and anyone else looking for information on how to make a water separator for air compressors.

I will not get into the extensive description of how the compressing of air generates water, except to say, that the higher the volume of air being compressed the higher the volume of water being sent into your compressor tank, or directly into your air mains. More information about water in the compressor or compressor air lines is found elsewhere on this site.

That flow of compressor-generated water down your air lines will have a negative effect on any downstream air equipment, whether they be air tools,  valves, cylinders or air drills and the like.

How to make a water separator for air compressors?

You can tinker and build your own water separator, I suppose. But I have to ask the question why?

Compressed air equipment manufacturers around the world make – largely low cost – and quite effective water separators.

They are called compressed air filters, and one is pictured above. We’ve researched and found the three best compressed air filters on the market.

Three Best Water Separators for Air Compressors

NANPU 1/2″ NPT Air Filter Pressure Regulator Lubricator Dryer Gauge Kit Water/Oil Trap Separator 3 in 1 Twin Unit

This 3-in-1 twin-air filter offers you the best experience by trapping both water and oil in your compressor system. It’s robust unit made of durable material, lasting for a couple of years unlike most cheap water separators on the market. Additionally, it’s cheaper than building a DIY water separator in our garage.

When there’s no air pressure in the system, the water bowl will excrete automatically, while the drainage column rises when the air pressure is on. As such, it automatically excretes the water to release the drainage column once the drainage is finished. It comes with 3/8” NPT taper and a maximum pressure range of up to 150 PSI.

PneumaticPlus SAU3030M-N03G-MEP Three Stage Air Drying System – Air Particulate Filter, 0.3 Micron Coalescing Filter & Air Pressure Regulator Modular Combo 3/8″ NPT – Manual Drain, Metal Bowl
With a maximum pressure supply of 250 PSI, the PneumaticPlus SAU4030M-NO4DG-MEP is a robust drying system that’s easy to install. The system shows the company’s dedication to offering flexible air filtration systems for compressed air applications, allowing you to customize the unit to your needs.

You can install this unit on a single plane without changing your existing piping as it’s designed to its regular NPT sizing. Its SAR regulators are mountable upwards or downwards, while the pressure can be regulated with the adjustable locking knob. Additionally, the SAF air filters efficiently eliminate moisture and harmful debris from the air supply without any leaks even at 250PSI.

PneumaticPlus PPC3C-N02G 3 Stage Air Drying System- Particulate Air Filter, Coalescing Filter & Air Pressure Regulator Combo 1/4″ NPT (High Flow), Poly Bowl with Guard, Manual Drain, Embedded Gauge
A three-stage water separator, the PneumaticPlus PPC3C-NO2G comes at a very reasonable price and performs better than most high-end units. In the first stage, its particulate air filter removes harmful oil and water condensate, rust, and pipe scale. It also prevents corrosive damage to your air tools and equipment in the system, with a maximum working pressure of 250PSI.

The system’s second stage eliminates any aerosols and oil droplets in the system, using a ¼” NPT port size. It also boasts of manual and automatic drain systems, while the third stage offers a locking adjustment knob. Even better, this air drying system is built to last for years without the need for replacement, though it depends on your compressor’s condition. However, this air filter won’t help you remove bacterial particles for sterile air.

How Compressed Air Filters Work

• Air from the compressor tank flows down the line and enters the cap of the filter.
• The flow of air is directed down into the bowl by the cap design.
• The compressed air is then forced to flow in a tight, cyclonic path within the bowl.
• Liquid water and debris that is typically in the air stream is thrown to the outside of the bowl by that cyclonic flow of the air.

The crud drains down into the bottom of the bowl past a barrier to help keep it separate from the air stream.

Auto drains help empty the filter bowl regularly, otherwise the bowls do need to be manually drained regularly to prevent water and crud from being forced back into the air stream.

Since water vapor in the compressed air stream can condense out anywhere along the flow path of the air, it is important to have a compressed air filter installed before each compressed-air-using piece of equipment or air tool to remove the water that condenses in the lines between the source and the air tool.

How to make a water separator for air compressors

Why bother? Just Google “compressed air filter” and you will find a host of suppliers. No need to reinvent this particular wheel!
However, if you really want to give making your own water separator for air compressors, let’s see how you can assemble your water separator in your garage. Follow these instructions;

Here is what you’ll need for this DIY.

• Nine ¾” Copper pipe in 2-inch pieces
• One ¾” Brass compression fitting (for the regulator)
• One ¾ Rapid air NPT filter regulator
• Six ¾” copper pipes (Type L ) cut in 72” for the height
• Three threaded 1/2” ball valves (both female ends)
• Three male adapters (3/4” -1/2”)
• Ten ¾” copper elbow (90 degrees)
• Three ¾” copper Tee
• One 2 ½“ to ¾” brass nipple
• One ¾” Brass street elbow (male and female end)
• One ¾” threaded male adapter
• One compressed air hose (3/4-inch)
• A threaded brass ball valve with both female ends (3/4”)

Note: Avoid using iron pipes in this DY as they corrode pretty fast inside, badly affecting the quality of your compressed air. Galvanized steel, stainless steel, and aluminum are a good alternative to copper, but they can be a bit expensive for some.

You will also need some Teflon tape, soldering flux, a solder strand, and a propane torch to join the copper piping. The soldering flux ensures the pipe doesn’t get oxidized when it’s heated.

Here is how to make the water separator once you’ve got everything you need.

• Start by joining three 2-inch copper pipes with a 90-degree copper elbow on each side. Ensure you apply a light coat of the soldering flux inside the copper elbow and on the outer side of the pipe before fitting them together.
• Take three more 2-inch copper pipes and fix a copper tee on each one of them. Add the remaining copper elbows on the other end of every copper pipe.
• With only three 2-inch pipes unused, take the joint with the copper tee and join each pipe. The second 2-inch pipe should be joined to the copper tee.
• Using five pipes, attach the joint with the copper tee to two type L copper pipes (cut in 72 inches). However, one of your joints should only be joined to a single long pipe, so ensure you attach that one on the side with the copper elbow.
• Take the other joints and attach to the other side of the type L copper pipes in a way that ensures there’ll be a continuous flow of air through the chambers. As such, one of the joints will be attached to a single pipe.
• Before hooking up any other equipment, solder the joints using your propane torch and solder to ensure the pipes don’t leak. For that, you’ll need to heat the pipes on the joints and melt the solder on top once it’s hot enough or when the flame on the side turns green. The solder will be sucked inside the tiny seam if the pipe is hot enough.
• Fix the three male adapters (3/4” -1/2”) on each outlet at the bottom and solder to avoid leaks.
• Add the threaded 1/2” ball valves below the male adapters. That’s why you need some Teflon tape.
• Cut the remaining 72-inch copper pipe into two halves and fix on each side of the set-up.
• One side will be attached to the brass street elbow to go to the regulator, while the other side attaches to the compressed air hose from your compressor.

Once you’re done, your setup should look similar to the diagram below.

You can also consider getting one of these water separators for your air compressor on Amazon without investing a fortune.