An airless spray tip controls two things: how wide the fan is and how much coating comes out. For roof painting, the right tip gives an even film at the thickness the coating's data sheet calls for. The wrong tip, or a worn one, means thin patches, overspray or runs. Reading the tip number takes the guesswork out.
The short answer
- First digit: fan width; last two digits: orifice size
- Bigger orifice means more coating per pass
- Match the tip to the coating's data sheet
- Worn tips spray unevenly, so carry spares
- Filters stop blockages before they reach the tip
How to read a tip number
Graco tip numbers have three digits. According to Graco, the first digit multiplied by 5 gives the fan width in centimetres when spraying 30 cm from the surface, and the last two digits give the orifice size in thousandths of an inch.
| Tip | Fan width | Orifice |
|---|---|---|
| 515 | About 25 cm | 0.015 in |
| 517 | About 25 cm | 0.017 in |
| 519 | About 25 cm | 0.019 in |
| 521 | About 25 cm | 0.021 in |
| 619 | About 30 cm | 0.019 in |
| 621 | About 30 cm | 0.021 in |
A wider fan covers more area per pass; a bigger orifice delivers more coating.
Common sizes for roof coatings
Roof primers and high-build membranes are thicker than wall paint, so roof restorers generally use larger orifices than for interior work. The coating's data sheet is the authority: it states the recommended tip range and spraying pressure. We stock Graco RAC X SwitchTips in 519, 521, 619 and 621, the WR1221 wide low-pressure tip with a 24 inch fan that sprays at up to 50% lower pressure, and Wagner HEA ProTips in 619 and 621, which Wagner says cut overspray by up to 55%.
Worn tips
Coatings wear the tip orifice as they pass through it. As it wears, the orifice gets bigger and the fan pattern changes, so you use more coating and the edges of the fan get heavy or uneven. If coverage is changing or the fan has tails at the edges at the same pressure, change the tip. Carry a spare of each size you use.
RAC X SwitchTips are reversible: turn the tip 180 degrees and trigger to blow out a clog, then turn it back to spray.
Filters and blockages
- Inlet strainer: stops debris entering from the bucket.
- Pump manifold filter: Graco Easy Out filters; 60 mesh is recommended for latex primers and paints.
- Gun filter: the last line of defence before the tip.
- Pump care: Throat Seal Liquid stops coating drying on the pump rod, and Atomex Pump Saver protects the pump between jobs.
Setting up for a roof job
- Read the data sheet for the primer and membrane: tip range, pressure, thinning and recoat times.
- Fit fresh filters at the inlet, pump and gun.
- Fit the right tip and pack a spare of each size.
- Test spray on cardboard and adjust pressure until the fan has no tails.
- Mask gutters, walls, windows and paths with tape and drop sheets.
- Keep the gun square to the surface at a steady distance and overlap each pass.
Cleaning up after the job
Flush the pump, hose and gun with the cleaner the coating requires, clean the tip and filters, and store the pump with a protective fluid such as Atomex Pump Saver to prevent rust and corrosion between jobs. Coating left to dry in a hose or filter is the most common reason a sprayer will not prime on the next job.
Extensions and guns
Walking on tiles cracks them and puts you at risk of a fall. WorkSafe Victoria treats falls from roofs as a serious hazard and puts edge protection ahead of ladders and harnesses. If you are not trained and equipped to work at height, use this guide to buy the right products and brief a roofer.
Tip extensions from 25 cm to 75 cm help reach eaves, gutters and awkward roof sections while standing safely. We stock the Graco Contractor gun with a RAC X 517 tip, the Contractor FTx with a 515 tip, the Wagner Vector Grip, BlueMax II hoses and whip hoses. See Graco spray equipment, and read choosing a roof coating system.
Common questions
What do the numbers on a spray tip mean?
On Graco tips, the first digit times 5 is the fan width in cm at 30 cm from the surface, and the last two digits are the orifice size in thousandths of an inch.
What tip size should I use for roof paint?
Use the range on the coating's data sheet. Roof membranes and primers usually need larger orifices than interior paint.
How do I know when a spray tip is worn?
The fan narrows or develops heavy edges, and you use more coating for the same area. Replace it and carry spares.
How do I clear a blocked RAC X tip?
Turn the reversible tip 180 degrees, trigger into a waste area to blow out the clog, then turn it back.
Which filter mesh should I use?
Graco recommends 60 mesh filters for latex primers and paints. Check the coating's data sheet.
Related
Sources: Graco: Tip hub infographic; WorkSafe Victoria: Prevention of falls in housing construction.
