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HOW-TO GUIDEWhy Is My Paint Sprayer Spitting Paint?
A sprayer that spits is telling you one of three things: the paint is too thick, air is getting into the fluid path, or the nozzle assembly is dirty or worn. The pump is delivering paint in slugs rather than a steady stream, so instead of a fine mist you get blobs, tails and dry patches. The fix is usually cheap and takes ten minutes.
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True spitting is intermittent: a normal fan, then a sudden gob, then normal again. A permanently ragged fan with heavy edges and a thin middle points to thick paint or a worn tip instead, and paint dribbling from the nozzle after you let go of the trigger is a leaking needle seal. Know which you have before pulling the gun apart.
Cause one: the paint is too thick
This is the most common reason by far, especially with HVLP and handheld electric units. Emulsion straight from the tin is thicker than most budget sprayers can atomise, so the pump forces it through in surges and each surge lands as a blob.
Most sprayers come with a viscosity cup. Fill it, time how long it drains in a continuous stream, and compare against the manual; around 20 to 30 seconds is typical for emulsion through a handheld unit. Without a cup, thin in stages: add roughly 10 percent water to water based paint, stir for a full minute, then test spray onto cardboard. Repeat in 5 percent steps rather than dumping a jug in at once. Use the recommended thinner for oil based paints, not water. And stir, do not shake, because shaking whips in air that leaves the nozzle as pops and spits.
Quick Tip
Strain paint through a fine mesh filter before it goes in the container, even from a freshly opened tin. Skin fragments and dried flakes off the rim are a major cause of intermittent spitting, and straining takes thirty seconds.
Cause two: air in the fluid line
If air is being drawn in anywhere between the paint container and the tip, it comes out as a splutter. Check these in order:
- Paint level. A container running low lets the pickup tube suck air. Top up before it gets near empty.
- Pickup tube position. The angled cut should point backwards when spraying downwards and forwards when spraying upwards, so the opening stays submerged.
- Container seal. A pot that is not seated squarely, or a perished gasket, loses suction. Check the thread for dried paint holding it open.
- Loose fittings. On airless units a loose suction hose or cracked inlet O ring pulls air in without leaking any paint out.
- Extreme angles. Tipping a handheld sprayer past about 45 degrees uncovers the pickup tube. Move your body rather than the gun.
Cause three: a partially blocked or worn tip
A half blocked tip lets paint through in bursts as pressure builds and releases. Reverse the tip if your sprayer allows it, trigger into a waste bucket to blow the blockage back out, then return it and test. If it stays blocked, soak the tip in the correct solvent, warm water for emulsion or white spirit for oil based, and clear it with a soft brush. Never poke a tip with a drill bit, needle or wire: the orifice is precision machined carbide, and once scored the fan pattern is ruined for good.
Worn tips give the same symptom. As the orifice erodes the fan narrows and atomisation suffers, which shows up as tailing and spitting. If a 300mm tip now lays down a 200mm band, it is finished. Tips are consumables, and a new one costs far less than repainting a wall.
Cause four: dirty filters and inlet valves
Most sprayers have at least two filters, one at the inlet and one in the gun handle, and both clog. Pull them out, check the mesh for splits, then clean or replace. A collapsed gun filter is a classic cause of stuttering delivery. On airless machines a sticky inlet ball valve gives a distinctive pulsing spit; tapping the inlet housing gently with a screwdriver handle while it primes will often free it.
Cause five: technique and settings
Some spitting is operator induced. Feathering the trigger part way gives a poorly formed fan and drips at the start of each pass, so squeeze fully before the gun reaches the surface and release after it has passed. Holding closer than about 150mm concentrates paint so heavily that minor irregularities read as spitting. Pressure matters too: too low and the paint will not atomise. Raise it in small steps until the fan edges are clean.
A sensible order to work through
- Stop, release pressure and unplug the unit.
- Check the paint level and top up.
- Test viscosity and thin if needed, stirring rather than shaking.
- Strain the paint.
- Clear or reverse flush the tip, and inspect it for wear.
- Remove and clean both filters.
- Check the container seal and all fittings for air leaks.
- Reprime, test on cardboard, adjust pressure.
Nine times out of ten the fault turns up in the first four steps. If you reach the end and it still spits, the pump seals or diaphragm are the likely culprit, and on a budget sprayer replacement is often more sensible than repair.
To stop it recurring, clean the sprayer the same day you use it and flush until the water or solvent runs completely clear. Dried paint left in the fluid path overnight is exactly what creates the flakes that block the tip on the next job.
Can thinning paint too much cause spitting?
Over thinning causes runs, poor coverage and heavy overspray rather than spitting. If you have thinned well past the manufacturer's guidance and it still spits, the cause is air ingress or a blockage, so stop adding water and look elsewhere.
Why does my sprayer only spit at the start of each pass?
That is usually trigger technique, or a little air sitting in the line while you pause. Pull the trigger fully just before the gun reaches the wall so the fan is formed on arrival, and keep the gun moving throughout the pass.
How often should paint sprayer tips be replaced?
There is no fixed interval, as it depends on the coating and the volume pushed through. Judge it by fan width: once the pattern is noticeably narrower than the tip's rated width, or the edges tail badly, fit a new one.