The Graco GX 21 sprayer is a beginner’s device, which means that many users have their first experience with the GX 21. Classic beginner mistakes always happen, so today we look at the errors to avoid when using the Graco GX 21 for the first time.

Top 5 des erreurs avec la Graco GX 21

Error #1 – Graco GX 21 used with too much pressure

A classic beginner’s mistake is to work with too much pressure. The Graco GX 21 pump achieves a maximum pressure of 207 bar, but many paints can be sprayed with much lower pressure.

In addition, the GX 21 comes with Graco’s low pressure green nozzles. These nozzles allow the paint to be applied at a reduced pressure compared to standard nozzles, so that it is usually possible to work with a lower pressure setting, well below 200 bar.

In the following video, we show you how to make the optimum pressure setting on an airless machine.


This reduces the formation of overspray. Paint consumption is reduced, you save on protective materials and time for masking work, and you get a uniform, quality spray. The principle is to apply as much pressure as necessary, but as little as possible.

Error #2 – Wrong nozzle with the Graco GX 21

The correct choice of nozzle is the key to an even spray pattern and maximum reduction of overspray. If the nozzle is too large, the flow rate of the sprayer is not sufficient and the spray becomes uneven. In addition, too much paint is applied and the paint starts to run down the wall. If the nozzle is too small, it will clog immediately.

Two factors play a role in the choice of the nozzle: the width of the spray and the size of the hole. The nozzle size is indicated by a combination of three numbers (e.g. 517, 410 or 521). The first number is the nozzle width, e.g. 5 for nozzle size 517 corresponds to a nozzle width of 50 degrees. The number 17 for nozzle size 517 indicates the orifice size, which is 0.017 inches. For spray width, if you are spraying a large area such as a wall, you need a wide spray to cover as much area as possible in each pass. If you are only painting narrow areas, such as baseboards, you need as small a spray width as possible so that you don’t spray too much paint to the left and right of the baseboard.

In addition, it should be noted that the flow rate of the Graco GX 21 is a maximum of 1.8 litres per minute. This flow rate is sufficient to feed a 0.021″ size nozzle. It is not possible to use larger nozzles.

The GX 21 is delivered with one LP 517 nozzle (suitable for different interior wall paints) and one FF LP 310 nozzle (suitable for different paints). The nozzles should be replaced regularly, as signs of nozzle wear are already visible in the spray pattern after a few hundred litres of paint.

In the following video we explain in detail how to choose the right nozzle for your project.


Error #3 – Graco GX 21 Filters not cleaned

Cleaning the GX 21 in general, and the filters in particular, is a prerequisite for the sprayer to be ready for the next use.

If the cleaning is not carried out or is insufficient, paint can dry in the device, the hose, the gun or the nozzle and disturb the operation.


Error #4 – Overloading the Graco GX 21 pump

The Graco GX 21 is an entry-level machine for small projects, i.e. for applying varnish, primer or interior wall paint in a two or three room flat or a single family home.

The Graco GX 21 is not designed for commercial projects with large areas such as warehouses, hotels, offices or schools. It is also not designed for facade painting, tissue adhesive, roofing or plastering. You can contact us for advice on choosing the right airless pump for your needs.

Error #5 – Wrong working technique

Incorrect spraying technique regularly leads to problems, especially for beginners to airless spraying. It is often found that the spraying is done at the wrong distance. The optimum distance between the gun/nozzle and the surface should be 25-30 cm.

If the spray gun is moved further along the wall, more overspray is formed. Because of the greater distance, the particles are more strongly braked on the way between the nozzle and the surface. This results in swirls and the formation of an overspray.

Distance entre le pistolet et le mur


The angle at which the spray gun is guided along the wall also influences the formation of the overspray and the even distribution of the paint on the surface. Therefore, the spray gun should always be guided at 90 degrees to the surface.

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