I'm spraying interior walls with an airless.

For interior latex wall paint, run a 517 (0.017" orifice, 10" fan) or 515 (0.015", 10" fan). The 517 is the industry standard for walls; drop to a 515 if you’re getting heavy runs or spraying thinner coatings.

Reading the number (e.g., 517):

1. First digit × 2 = Fan width (inches) at 12" distance. 5 × 2 = 10" fan pattern.
2. Last two digits = Orifice size in thousandths of an inch. 17 = 0.017".

Practical rules:

• Orifice controls flow rate. Latex needs .015–.021. Too small = clogging/poor atomization; too big = runs/waste.
• Fan width controls coverage speed. 8–12" (4–6 first digit) is standard for walls. Wider fans (619+) are for ceilings/siding; narrower (311) for trim.
• Worn tips grow the orifice. A worn 517 sprays like a 519—replace tips every 15–25 gallons.

Setup checklist:

• Strain paint.
• 2,000–3,000 PSI at the gun (not max pump pressure).
• 12–14" gun-to-wall, 50% overlap, trigger after moving.
• Back-roll immediately for uniform sheen/stipple.

If you’re spraying unthinned heavy bodied latex or elastomeric, step up to a 519 or 521. Always verify tip rating matches your pump’s max flow (GPM).

For interior latex wall paint sprayed with an airless sprayer, use a 515 or 517 tip — these are the most common and effective for smooth, even coverage on drywall or plaster.

How to read a tip number (e.g., 517):

Airless spray tips use a three-digit code:

• First digit (5): Spray fan width when held 12 inches from the surface. → Multiply by 2 to get approximate width in inches. → 5 × 2 = 10-inch fan width (ideal for walls — wide enough for efficiency, narrow enough to control overspray).
• Last two digits (17): Orifice size in thousandths of an inch. → 17 = 0.017 inches (controls flow rate and pressure needed).

Why 515 or 517 for latex walls?

• 515 (0.015" orifice, 10" fan): Best for thinner latex or smooth finishes — less prone to tip clogging, great for ceilings or fine textures.
• 517 (0.017" orifice, 10" fan): Standard for most interior latex wall paints — handles slightly thicker formulations well, provides good hide and coverage without excessive pressure.

Pro tips:

• Always strain paint through a mesh filter before spraying to prevent clogs.
• Start at 1500–2000 PSI (adjust based on paint viscosity and tip wear — if paint spits or tails, increase pressure slightly; if it fogs or oversprays, reduce).
• Keep the gun 12–18 inches from the surface, moving at a steady pace — overlap each pass by 50%.
• Clean tip immediately after use with water (for latex) to avoid drying and blockage.

> ⚠️ Note: If spraying textured walls (e.g., knockdown, orange peel), consider a 519 or 619 for heavier build. But for smooth interior latex walls, 517 is the sweet spot.

Reference: Graco, Titan, and Wagner airless sprayer manuals; PDCA (Painting and Decorating Contractors of America) guidelines.