An airless paint gun follows one fixed order: assemble it, flush the line, prime it, bleed the pressure, then test-spray and adjust the fan.
For the full breakdown, see our best Airless Paint Gun guide.
Running the setup steps in a fixed order prevents both before the first pass on a wall.
Anyone working out how to use an airless paint gun can treat the sequence below as the short version of the manual. It comes from Graco’s published startup guidance for its airless sprayers, and it holds whether you’re running a Magnum homeowner unit or a contractor rig. Model changes the details — Graco notes that the exact startup steps depend on the sprayer you own and whether it has been used before.
Setting Up An Airless Paint Gun: The Order That Matters
Setup runs through three phases on nearly every airless unit: connect the hose and gun, flush and prime the sprayer, then install the tip and guard. Graco lists those three prep steps in that order.
The fuller startup sequence, step by step:
- Engage the trigger lock and switch the sprayer off.
- Turn the pressure control to its lowest setting and reverse the tip.
- Relieve pressure with the gun held against a grounded metal pail, triggering until nothing sprays out.
- Set the prime valve to PRIME/DRAIN, put the intake hose in the paint, and drop the drain tube in a waste pail.
- Power on and raise pressure until paint circulates smoothly.
- Switch to SPRAY and run until paint reaches the gun.
- Spray about 20 seconds into a waste bucket.
- Install the tip guard, insert the tip, and tighten the assembly.
When it works, paint moves through the hose in a steady stream and the pump note drops to an even hum.
High-efficiency sprayers reorder the first few moves: parts stored inside the tank get attached first, the hose connects with wrenches, tap or distilled water goes in the tank and gets purged through the hose at PRIME, then the water is swapped for paint and the pump runs until paint reaches the tube.
Graco’s airless sprayer startup sequence spells out each of those moves, and it’s worth reading against your own manual because the control positions change between models.
| Stage | What You Do | What Tells You It Worked |
|---|---|---|
| Assembly | Thread the hose onto the pump and the gun | Fittings hand-tight, then snugged with wrenches |
| Flush | Push water or solvent through pump, hose, and gun | A clear stream leaves the drain tube |
| Pressure relief | Lock the trigger, switch off, trigger into a metal pail | The gun stops hissing |
| Priming | Valve to PRIME/DRAIN, intake in paint, drain tube in waste | Paint circulates and the pump note steadies |
| Line fill | Valve to SPRAY, run until paint reaches the gun | Paint, not water, exits the gun |
| Tip install | Thread on the guard, insert the tip, tighten | The tip seats flat and the guard faces forward |
| Test spray | Spray scrap wood and raise pressure in small steps | Crisp fan edges, no tails, no runs |
Can You Change The Tip While The Sprayer Holds Pressure?
No. Graco’s procedure calls for pressure relief at the gun before any tip change, filter swap, or pause in the work.
The relief routine is short: engage the trigger lock, switch the sprayer off, set the prime valve to PRIME/DRAIN, and hold the gun against a grounded metal pail while you trigger it.
Never point the gun at a person or animal, never put a hand or finger over the spray tip, and wear a respirator or mask while spraying. The paint and solvent manufacturers’ own safety instructions sit on top of the sprayer manual.
Graco’s manuals also name the RAC IV 515 SwitchTip and the SG2 metal spray gun, so match replacements to the numbers already on your gun.
Pressure, Fan Pattern, And The Last Check Before You Spray
Start at low pressure and raise it in small steps during a test spray on scrap wood, stopping as soon as the fan lays down an even coat.
Tails — thin streaks along the edges of the fan — mean pressure is too low or the paint is too thick. Runs and drips mean it’s too high. Overlap each pass by about half a fan width to avoid stripes, and keep the gun moving at a steady pace.
If you’re still choosing hardware, our tested airless paint gun roundup compares the models worth the money for homeowners and contractors.
The whole job reduces to five moves: connect, flush, prime, relieve, spray — then relieve again before you touch the tip or stop for the day.
FAQs
How Do You Know When An Airless Sprayer Is Primed?
Paint reaching the gun is the sign. With the prime valve at SPRAY and the pump running, watch for a steady stream rather than sputtering, and listen for the pump note to settle. If nothing arrives, check that the intake hose sits below the paint line and that the drain tube isn’t blocked.
What Happens If You Change A Tip With Pressure Still In The Line?
Paint can fire out of the tip at full pressure the moment the guard comes loose, which is why the trigger lock goes on and pressure gets relieved first. Treat every pause, filter change, or tip swap as a full relief cycle rather than a shortcut.
Do You Need To Thin Paint For An Airless Sprayer?
Check the paint label first, because some manufacturers specify thinning for particular products or sprayer types. Tails in the fan are the usual signal that the paint needs more pressure or a little thinning.
References & Sources
- Graco. “How to Start Up a Paint Sprayer.” Source for the trigger-lock, prime-valve, and pressure-relief startup sequence.
- Graco. “How to Use an Airless Sprayer” (Magnum homeowner support). Covers the connect, flush, and prime prep steps and model-by-model variation.
- Graco. “307735EN-C Sprayer Manual.” Lists the RAC IV 515 SwitchTip, SG2 metal spray gun, and 517 spray tip.