How to set up an air compressor for spray guns and painting
Is there such a thing as the perfect paintjob? That’s the big question for DIYers and professionals alike any time it comes to adding a lick of paint to the walls of the house, the garden fence or when spray painting a car. If you’re yet to ditch the brush or roller and paint tin, the first, and rather big, step on that journey is to invest in an air spray gun.
If you’re not already familiar, spray painting guarantees a much more controlled and even finish on your work than any hand-applied brush/roller job, but just investing in any old spray paint kit and assuming it will immediately produce optimal results won’t get you too far. To avoid improper application and the dreaded “orange peel” effect, you need the right kit, and that means getting a spray paint compressor that meets the specifications your spray gun setup requires.
Our guide will walk you through everything you need to know regarding paint compressors and the technical delivery elements required. Then, once you know what you’re doing, we’ll tell you about a few of the best spray gun and compressor kits available on the SGS website, so you can make a masterpiece of any paint job you take on going forward.
What is a gun compressor?
When we talk about an air compressor for painting, we’re not actually talking about a specific type of compressor exclusive to spray painting function, but rather a suitable air compressor for spray gun use. Air compressors use a power source to create pressurised air in a storage tank, which can then be used for a variety of applications, including spray painting. Different air compressors have different pressure limits, which is where choosing the right one comes into play.
Most air paint spray guns use a “high volume, low pressure” (HVLP) delivery mechanism, thus it’s important to find a spray paint compressor that delivers the required pressure and volume of air in order to create a consistent paint flow that will give you a perfect finish.
What is HVLP?
HVLP spray guns atomise paint coatings by employing a high volume of air at low air-cap pressure, typically in a pressure range that’s around quarter or less than that of conventional methods. This means the sprayed material has less velocity so is less likely to "bounce back", which increases your paint’s transfer efficiency. The HVLP method also delivers a much softer spray which reduces material waste. They do, however, demand a higher air volume than conventional sprayers, meaning a bigger compressor is required, but more on that below.
What are the air compressor requirements for spray painting?
There are three key measurements to consider when compressed air spray painting. The first is pounds per square inch (PSI), the second is cubic feet per minute (CFM) and third is tank size. As you can guess from the “low pressure” part of HVLP delivery, you won’t need a lot of pressure to get the job done, but you still need to ensure you have a high enough PSI to ensure consistent delivery.
The CFM measurement is arguably the most important factor to consider when choosing your compressor. CFM measures the volume of air produced by the compressor per minute and the quantity of air the compressor can produce at a given PSI. The CFM rating of your compressor should be higher than, not equal to, the CFM requirements of your air spray gun, otherwise you risk both pressure drop and volume loss, which are the two main causes of imperfect coverage. As alluded to above, the “high volume” element of HVLP spray guns is a big clue that a larger compressor will be required for proper use.
Finally, tank size matters in relation to spray painting because spray gun operation requires a constant flow of air rather than intermittent supply as with many other pneumatic tools. Thus, your compressor needs to have an adequate storage to keep up with the gun.
How much CFM do I need for spray painting?
Paint gun CFM requirements differ from model to model, with small spray guns naturally requiring a lower CFM than bigger options. While some air spray guns have a rating of lower than 10 CFM, we’d recommend your compressor CFM for spray painting is at least 12 CFM.
For professionals, this figure may need to be higher – the important thing is you’ve checked your spray gun’s CFM requirements and chosen a compressor that exceeds that figure.
What is the best air pressure for spray painting?
Again, it’s essential you check your specific model’s recommendations, but your HVLP spray gun PSI will likely sit between 25-30 PSI for something like using an air compressor for spraying cars, rising to 40 PSI in some cases where higher atomisation is needed.
How to spray paint with an air compressor
Wondering how to use a spray gun with your new compressor? Here’s what you’ll need to get started:
- Safety gear: a respirator or mask, goggles and gloves
- A suitable air compressor for your spray gun
- Spray gun attachments: filter, regulator, quick disconnect fittings – although you might not need all of these depending on your requirements.
Here’s the process:
- Apply your safety gear before starting any work
- Connect your air spray gun to your air compressor via the hose and other attachments (see diagram above)
- Ensure your compressor is delivering adequate CFM
- Mix your paint/primer and solvent to the recommended ratios.
- Test your pressure paint sprayer pattern on a piece of cardboard to check your compressed air spray is delivering a consistent paint flow. You can adjust your spray pattern on most HVLP spray guns via a knob on the side of the gun.
- Apply an even coat of paint to your chosen surface, applying a second coat if required 12-24 hours later (once the first coat is dry).
Your air spray gun and paint compressor checklist
As we’ve already established, ensuring you’ve got the adequate CFM and volume in your compressor tank to do the job consistently is essential. However, despite all your best efforts and preparations, you might find that you’re still facing problems with air pressure.
If you are struggling to get the results you’re looking for, there’s a checklist of things to go over to ensure you’re getting optimal performance from your spray gun and air line setup.
How narrow is the air hose?
The hose you’re using can be the source of pressure issues if too narrow or too long. The inside diameter (ID) of your hose is the measurement to look out for, with a smaller ID translating to less air getting through the line, and therefore less pressure. For example, if you’re using a 5/16 inch (7.9mm) hose, you’ll get less pressure than a wider diameter 3/8 inch (9.5mm) option.
With HVLP spray guns, an ID of more than a ¼ inch is advisable, with a hose larger than 5/16 inch needed to meet typical HVLP volume requirements. A word of warning, though – bigger is not always better. Bigger can often mean a longer hose, which also needs to be taken into consideration.
Is the Air Hose too long?
As the compressed air travels through a hose, the pressure decreases as distance increases from the compressor, meaning a lengthy hose can be detrimental to a high-pressure paint gun. As a rule of thumb, it’s best to use as short a hose as feasibly possible with a decent width ID.
8mm diameter, 10m long rubber air hose comes with quick release connectors.
10m polyurethane recoil type hose
fitted with a two female 1/4" BSP threads.
20 metres of durable braided PVC hose
and snap fit air inlet/outlet connections.
10mm diameter, 10m long PVC air hose comes with quick release connectors
6mm diameter, 15m long rubber air hose comes with quick release connectors.
Quick disconnect fittings (QDs) – do you need them?
Quick disconnect fittings (QDs) are hand-fitted air connectors that allow for fast and easy connection and disconnection of the air line. They replace traditional fitting connectors which often require the use of tools for assembly and disassembly, making them decidedly quicker to use and benefit the user experience considerably. However, depending on how many are used and their design quality, QDs can be a hinderance when it comes to maintaining air pressure.
Depending on the design and volume requirements of your pressure spray gun, the pressure drop from a QD can lie between 1-25 PSI. So, it’s important you pick your QD design carefully, choosing the least restrictive unit possible. Using many air connectors can also cause pressure to drop.
One common pressure issue relating to QD use is a small aperture in the female portion of the component, with the narrow diameter restricting air flow, just as with a small ID hose. If you are going to use QDs, ensure you are using “high-flow” options that offer the biggest practical diameter to minimise any pressure loss.
The fundamental question is: are QDs really necessary? If you’re only planning to remove your air hose from your spray gun and compressor once or twice a day, the simple answer is no.
Is the air regulator high flow and of good quality?
Air spray gun regulators provide precise adjustment of the air flow and air pressure which ensures consistent results. However, their design can also restrict air flow and create excessive pressure drop. There are two types of paint gun filter regulator - wall-mounted and gun-mounted.
Typically, larger wall-mounted regulators better provide constant air pressure to the gun, minimising the dreaded pressure drop. Your spray gun pressure regulator should be capable of flowing enough air for the spray gun to operate efficiently and offer capacity greater than your air spray gun’s demand.
To determine if the regulator is too restrictive, compare in-use and not-in-use readings on your spray gun regulator with the gauge. The difference between the two readings should be 5 PSI or less.
Although regulators control the air pressure, the system may still experience fluctuations, particularly when an air-adjustment valve-type restrictor is being used. The air will exit the air cap with an initial burst of pressure, which then levels off to the adjusted pressure, but this may vary because of changes in system pressure.
Air Filter, Water Trap, Regulator & Lubricator
Air Filter, Water Trap & Regulator
High Quality Air Lubricator
What is the Performance Specification of the Air Compressor?
The fundamental requirements of your compressor are that it needs to supply sufficient, clean (oil-free) and dry (water-free) air, while also being the correct size to facilitate the air pressure and volume requirements of the whole system. This is important because, as previously mentioned, the restrictions of certain QDs, a narrow hose ID and the regulator can all play a factor in alleviating pressure, which is why it’s necessary to have a spray paint compressor that produces a higher CFM than your HVLP spray gun.
To keep the air clean, the air tank must be drained of any water and the spray gun filters checked to determine they are spotless and functional. It’s also recommended to have a final air filter installed at the gun itself. To read more about the various specifications of air filter setups, check out our air compressor buying guide here.
Spray Gun Kits
If you're new to the world of paint spraying, we’d recommend starting with our ready-made 6 litre oil-less air compressor & spray gun kit. The kit comes complete with a professional air spray gun, a spray gun regulator, a 10m hose and a spray gun cleaning kit, as well as euro quick-release couplers. An ideal starter option for anyone looking for a lightweight piece of equipment for occasional small, at-home DIY projects.
Secondly, our punchy 24 litre, 9.6 CFM compressor is fully equipped with a HVLP, gravity-fed professional spray gun, 10m rubber air hose, spray gun regulator with gauge, mini air filter and water trap and 2 quick couplers. Another good choice for anyone recently starting out with spray painting, the kit offers a superb combination of performance, safety and value.
Our 50-litre, high-flow, reciprocating air compressor has the capacity and delivery to ensure you always get fantastic results. The compressor boasts a large 50L tank that makes this kit a top contender for serious enthusiasts and semi-professional sprayers. Offering plenty of bang for your buck, the kit is fully equipped with a HVLP, gravity-fed professional spray gun, a 10m 6mm rubber hose with quick couplers, a mini air filter setup and 1 litre of compressor oil. For help getting going, our compressor spray gun guide has all the info you need to get up and running.
Finally, our 100L, high-flow air compressor and spray gun kit will provide you with everything you need to quickly and efficiently complete any spray painting work you want to carry out. The 100L air compressor kit comes complete with a HVLP gravity fed spray gun, two 6m rubber hoses with quick couplers, a spray gun filter, water trap, regulator & lubricator, euro quick couplers, mini air filter and 1 litre of AC 2068 compressor oil. All of that makes this kit the best choice for regular and semi-professional sprayers alike.
Don't forget; regardless of what size or style of spray gun and air compressor you own, keeping it clean is vital for avoiding blockages and keeping it performing at an optimal level. With that in mind, we’d suggest one of our high-quality cleaning kits for spray guns which will give you everything necessary to maintain your spray gun and compressor between uses with minimal fuss. The kit contains eight key pieces which are designed to ensure longevity and the best possible results.