The Millin Step-by-Step Guide to Assembling Your Airless Paint Sprayer

The Millin Step-by-Step Guide to Assembling Your Airless Paint Sprayer

Posted by Matt Piggin & Nikki Michaels on 25th May 2020

The Millin Step-by-Step Guide to Assembling Your Airless Paint Sprayer

In our last post, we gave you step-by-step instructions for cleaning your spray unit once you’ve completed a job — and now we’re following it up with a quick guide to setting up for spraying.

This easy-to-follow breakdown offers a look at how to properly set up your spray unit so that you avoid costly machine malfunctions and other errors that can mean digging deep into your pockets for maintenance and repair charges. Keep reading for Millin’s newest step-by-step guide.

What’s involved in setting up your spray unit?

First: lubrication. 

Always add a couple of drops of lubricating oil at the start of every day; this puts a protective film around the piston and packings and helps reduce wear and tear.

Wagner EasyGlide and Graco Throat Seal are both great options.

Second: Filtration.

There are three filters you need to worry about when it comes to assembling your spray unit: the main filter (aka ‘rock filter’), the high-pressure filter, and the gun filter.

Before installing filters, check that they’re clean and free of any damage; excess build-up of old paint will reduce the flow of product and cause your machine to work harder. Be sure to always replace damaged filters as well. Now, on to the three filters:

  • The main/rock filter is the one that sits in the paint at the end of the suction hose or pipe. It’s the first line of defense and can be easily screwed on and screwed off.
  • The high-pressure filter is on the body of the pump and filters the paint prior to entering the gun hose. Not all machines have these filters; in fact, it’s usually just the bigger ones that do.
  • The gun filter sits inside the handle of the gun. There are a variety of gun filter sizes that will correlate to the viscosity of the product you’re spraying. Match the filter correctly to avoid blockages and to maintain a consistent spray pattern.

You’ll also need your hose; these do wear, so check the condition often to make sure there are no potential break points (including any joiners when using multiple hoses).

Lastly, choose whatever spray tip you’re going to be using.

How to assemble your spray unit

  1. First: have you lubricated your machine? If not, do so.
  2. Make sure your main filter is fitted.
  3. If your machine has a high-pressure filter, install it and screw the housing on very tightly.
  4. Connect your hose. You won’t usually need thread tape for this, but you must use a spanner to tighten it.
  5. Place your gun filter inside the handle of the gun. (Most gun filters are one-directional and if installed upside down will stop the gun from spraying.) Screw the gun handle up tightly.
  6. Place the main/rock filter and the prime hose in your bucket of paint/liquid. (The prime hose functions to siphon the air out of an airless system.)
  7. Switch the unit to prime, turn it to a low pressure, and send pressure through the prime hose. (Typically when the switch is facing forwards, it’s sending pressure to the gun; when it’s facing down, it’s going through the prime hose.)
  8. Once primed (no more air bubbles coming out into the paint), turn the machine off and switch the unit to send the pressure through to the gun (switch facing forwards). Again, turn the machine to a low pressure.
  9. Once the gun is primed, you’re ready to spray. Squeeze the gun handle in short bursts to make sure everything’s working (NB: always spray at the lowest possible pressure while still getting your perfect spray pattern), and then get started with your job.

A pro tip on installing gun tips: keep the tip holder finger-loose. This way, you can push the gun tip right in and simply finger-tighten it. No need for a spanner.

Any further questions about spray unit assembly? Are there any other step-by-step guides you’d find helpful? Email me at to let me know.