In the next article, we discuss relief valve replacement on airless paint sprayers. Using a Graco pump as an example, we discuss the function and structure of the relief valve or its flushing.
We also show you how to remove an old valve and how to install a new one.
What is the function of a relief valve on an airless pump?
The pressure relief valve, also known as the decompression valve or drain valve, is used to relieve pressure and to flush and clean the sprayer. The pressure relief valve controls the flow of paint before the gun or directly into the paint can. For this purpose, the valve has two settings, flush and spray.
In the “spray” setting, the paint is sucked in by the unit’s pump and pushed upstream of the gun. The paint is then sprayed at the nozzle.
The second setting does not pump the paint or material in front of the gun, but returns it to the paint can via a return hose. This function is used to relieve the pressure at the airless device (e.g. during a work break).
In addition, this function can be used to pump the paint out of the sprayer and to rinse the device with water or solvent. We have put together a detailed presentation of the cleaning step in the following video.
When should the airless relief valve be replaced?
If a relief valve is no longer working, it cannot be switched. The material can then only be transported to the gun or to the paint bucket. It is then no longer possible to switch between these two functions.
In addition, the valve may be blocked in a half-open position. This results in material flowing back into the bucket, even though the valve is set to “spray”. In this position, the paint should be transported exclusively to the front of the gun.
Another type of error is when the valve is completely blocked in both positions. In this case, the material does not flow through the valve in either the “flush” or “spray” position.
The causes of these malfunctions range from clogging or blockage with foreign bodies, paint residues or plaster, to mechanical damage or wear of the valve.
If any of the described defects occur, the valve should be disassembled and checked. If you are lucky, it is only a contamination that can be quickly removed by cleaning the valve. With less luck, the relief valve is worn, mechanically damaged or so clogged with paint residue or foreign matter that it can no longer be cleaned. In these cases, the only thing left to do is to replace the damaged bleeder valve with a new one.
How do I remove or reinstall the new relief valve?
Using a Graco Mark VII as an example, the photo shows how to disassemble a damaged pressure relief valve and how to install a new one. To disassemble a damaged pressure relief valve, first remove the plastic cover/handle from the valve. This is done by removing the metal rod that holds the plastic cover in place.
The metal rod can be easily removed with a punch and hammer. If a punch is not available on the job site, a nail can be used as a backup. Once the metal rod is removed, the black plastic handle can be removed. The white plastic cover on the bottom can also be removed.
The valve can now be unscrewed counterclockwise with a wrench. Before doing so, make sure that the pressure of the sprayer has been completely released and that the pressure indicator is at zero. Once the valve is unscrewed, it can be checked for dirt or damage. Any dirt must be removed. If this is not possible, the valve must be replaced in case of wear or mechanical damage.
Choosing the right relief valve?
To help you find the right pressure relief valve for your airless sprayer quickly and easily, we have compiled a small overview of current spraying devices and the corresponding pressure relief valves.
Just click on the link to go to the corresponding pressure relief valve.
- Relief valve Graco GX 21
- Relief valve Graco GX FF
- Relief valve Graco ST Max II 395 PC Pro
- Relief valve Graco ST Max II 495 PC Pro
- Relief valve Graco ST Max II 595 PC Pro
- Relief valve Graco Ultra Max II 695
- Relief valve Graco Ultra Max II 795
- Relief valve Graco Ultra Max II 1095
- Relief valve Graco Mark V
- Relief valve Graco Mark VII
- Relief valve Graco Mark X
- Relief valve Wagner PS 3.20
- Relief valve Wagner PS 3.21
- Relief valve Wagner PS 3.23
- Relief valve Wagner PS 3.25
- Relief valve Wagner PS 3.29
- Relief valve Wagner PS 3.31
- Relief valve Wagner PS 3.34
- Relief valve Wagner PS 3.39
- Relief valve Wagner HC 750
- Relief valve Wagner HC 950
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Questions or queries?
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