Demystifying the PRV, a complete technical breakdown

The Pressure Release Valve or PRV is often spoken about, but not as often understood. The purpose of this little device is written right in its name. In the case of over pressurization, it is there to release the pressure in order to stop the marker from firing at unsafe velocities. This part is commonplace in pretty much every blow forward engine used in paintball. 

If your PRV is leaking, the cause is one of three things. Your regulator shim stack is incorrect, your valve seat is worn, or your PRV needs to be rebuilt. As the PRV’s sole purpose is to prevent over pressurization, we strongly recommend that you check both of the internal factors that could lead to a leak before replacing or rebuilding the PRV. The PRV is intended to indicate whether these issues are happening, so we always want to assume that it is one of them first. 

As an obvious first step of diagnosis, we want to confirm that the velocity of the marker is set below 350 Feet Per Second. The PRV is factory set to begin to leak between 350 and 370. The factory setting for the PRV is to turn the screw into the PRV body until it is one thread below the tip of the PRV. There is absolutely no reason to set the PRV any differently than this, and it should always be set in this spot. 

The PRV will leak in two ways that will help us indicate the cause of the issue. There will either be an immediate leak, which indicates an immediate over-pressurization, or there will be a slow buildup of a leak, which indicates a leak somewhere within the valve that is causing a buildup of pressure. 

If the leak is immediate, it is most likely that your shim stack is incorrect. This means that either the shims are not installed in the correct pattern ()()()(), or one of the shims has shifted out to the side. You can confirm this by removing the regulator cap and looking from the side to confirm the order, and then straight down from the top to ensure none of the shims are sticking out. A video on this process can be found here:

If the leak is gradual, your valve seat is likely leaking. This is a result of a buildup of debris inside the regulator. You can first attempt to rectify this by applying several drops of oil into the ASA of your marker, then firing a few dozen shots. If this doesn't solve it, it’s time to replace your valve seat. You can see how to do that here:

If you’ve completed the above steps and your PRV still leaks, it is likely that your PRV is worn out. This doesn't happen very often, but after a marker is 2-3 years old it is possible. We always want to do the above steps first to eliminate a regulator fault as the cause of the issue, but if both haven’t resolved it, the last step is a simple one. You can choose to replace or rebuild your PRV by purchasing the necessary parts at your nearest MILSIG Dealer. Both a complete PRV and the PRV Seat can be purchased depending on the level of effort that you want to put in. The Complete PRV is as simple as removing the old one and installing the new one. 

If you’ve chosen to rebuild your PRV, the process is pretty simple. We recommend removing the entire PRV from the marker to accomplish this as it will make it easier to work on. To perform the rebuild you will need a 4mm Allen wrench, and a 10mm wrench, or vice. While holding the PRV body, unscrew the screw from the PRV counter-clockwise. Once the screw is removed, the spring should just fall out, and leave a small brass piston inside the PRV body. The piston can take a bit of wiggling, but it will come out of the body. Once the piston is removed you’ll notice a piece of black rubber on one end of it. You’ll want to remove the rubber piece and replace it with your new one, then reassemble. Remember that the rubber seat needs to face inwards during the reassembly process. When everything is back together, tighten the PRV screw until it is inset into the PRV body by one thread. 

From here, you’re all done. If your leak still persists, it’s likely that a step was missed somewhere along the way. If you get stuck, feel free to contact us for help in resolving your issue.