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When working with a paint sprayer, there are two options for how the paint (or other liquid) moves through the spray gun. Read this article to understand each option, as well as their similarities and differences. You’ll also learn the major differentiating factor between siphon feed and gravity feed options, when to use each type of feed, and which is better overall.
Contents
What Is Siphon Feed?
In a siphon feed paint sprayer set up, the reservoir or paint, stain, or wood finish is located below the nozzle. Pressurized air from a compressor is used to form a vacuum at the top of the reservoir, which sucks up paint. The pressurized liquid is then fed through the mechanism of the spray gun, and comes out of the nozzle in a fine mist.
For a siphon feed sprayer to work, you need to leave some air in the reservoir. Fill siphon feed sprayer reservoirs only about two-thirds of the way full.
You also need the container to be intact and tightly sealed, so that the pressurized air can successfully create the vacuum that sucks up the liquid.
What Is Gravity Feed?
Gravity feed spray guns have the reservoir of liquid located above the nozzle. When the trigger is squeezed, paint is allowed to flow into the stream of pressurized air. As it exits the nozzle, the paint particles become atomized, moving in a controlled stream to settle on your material.
Siphon Feed vs Gravity Feed
High volume, low pressure (HVLP) paint sprayers are quickly outpacing conventional airless sprayers, in part due to legislation limiting the use of non-HVLP sprayers in certain areas. HVLP sprayers are usually gravity fed, and airless sprayers are more likely to be siphon fed, so this may be one factor you use to make your decision between the two.
However, this isn’t always the case. When you’re deciding what kind of sprayer to purchase, understanding the similarities and differences between siphon feed and gravity feed is an important part of making the best decision for your needs.
Similarities
The similarities between siphon feed and gravity feed reservoirs on paint sprayers include the capacity of the reservoir, eventual atomization of the liquid and their shared compatibility with a wide variety of materials.
Capacity
The capacity of paint reservoirs varies from one model of paint sprayer to the next, and is dependent on the manufacturer. Whether the sprayer has a gravity feed reservoir or a siphon feed reservoir has no impact on the size of the container or how much fluid it can hold.
Atomization
Atomization occurs when pressure is applied to liquid, and that liquid is forced through a spray tip. The resulting fine spray is what allows sprayers to achieve such a smooth and even finish. Whether gravity fed or siphon fed, the purpose of all sprayers is the same: to atomize paint and direct it toward your chosen surface.
Material Compatibility
Many people have strong preferences about whether they prefer to use a siphon feed or gravity feed spray gun, especially if they have years of experience spraying paint.
While these preferences are certainly valid, it is possible to get good results from either a gravity feed or a siphon feed paint sprayer.
The manufacturer’s instructions will include information about how to properly set up and prime the machine, as well as a recommended range for the viscosity of fluid to be sprayed. By following these instructions and using good spray technique you can achieve an even, dustless finish.
Differences
While siphon feed and gravity feed reservoirs share some things in common, there are important differences between them as well. These include; the amount of pressure required to operate the spray gun, the amount of overspray generated, and their relative maneuverability.
Pressure
A certain amount of pressure is required to turn liquid paint into a sprayable mist. Siphon feed spray guns require even higher pressure levels in order to create the vacuum that sucks up paint. Higher pressure leads to a more forceful spray, which increases the amount of material that drifts away from your chosen surface.
Gravity feed spray guns require less pressure to operate than most siphon feed spray guns. The exceptions to this rule are siphon feed models with a pressurized cup, served by a separate hose running from the air supply to the interior of the cup.
Amount of Overspray
As stated above, siphon feed sprayer systems require more pressure than gravity feed paint sprayer systems. This pressure is used to create the vacuum that moves liquid from the container or reservoir, through the spray gun and nozzle, and out the tip.
The mist that exits from the spray tip is therefore under more pressure, and moves at a higher speed, making it harder to direct and control the flow.
Thus, siphon feed sprayers tend to create more overspray. Overspray is defined as mist that settles onto anything you weren’t attempting to coat.
Maneuverability
Both siphon fed and gravity fed sprayers are limited somewhat in their movements by the placement of the liquid reservoir. In siphon feed designs, the container hangs down from the nozzle, and the hoses usually run alongside it.
In gravity feed sprayers, the container sits on top of the spray gun while the hoses come out of the bottom. This makes gravity feed sprayers a bit more difficult to maneuver than siphon fed versions, as you have to worry about both the top and bottom of the gun.
Major Differentiating Factor
It’s best to apply paint, stain, or varnish at the lowest possible pressure. This gives you the most control over the spray and reduces the amount of troublesome overspray. Since gravity feed paint sprayers require less pressure to operate than siphon feed sprayers, this is the biggest distinguishing characteristic between the two.
When to Use Siphon Feed
Use a siphon feed spray gun for large surfaces, when control and precision are not your biggest concerns.
If you are already familiar with siphon feed sprayers, you may be more comfortable continuing to use a conventional model.
Siphon feed sprayers can also be easier to maneuver, since the hose and fluid reservoir both hang down from the bottom of the spray gun.
For certain types of automotive coating, such as very thin clear coats, a siphon feed sprayer achieves better coverage in fewer coats.
The higher pressure of siphon feed sprayers makes them ideal for creating splatter patterns.
When to Use Gravity Feed
Most HVLP sprayers are gravity fed. Some localities have restricted the use of airless sprayers, due to the significant increase in overspray created with this kind of machine.
When you’re doing detail work, the reduced pressure and reduced overspray of a gravity fed sprayer is beneficial.
Which Is Better, Siphon Feed or Gravity Feed?
If you are doing specialized automotive work, such as using super-thin clear coat or creating a splatter pattern, siphon feed sprayers are the best tool for the job.
For everything else, choose a gravity feed sprayer. Gravity feed sprayers are better than siphon feed sprayers in almost every instance. They are able to operate at reduced levels of pressure, create less overspray, and give the operator more control over the direction of the spray. They are also easier to maneuver.
The flow of liquid is more consistent with gravity feed sprayers than with siphon feed sprayers. This is because they do not require consistent pressure to create the vacuum that sucks up fluids.
