For industry and commercial cleaning we recommend choosing a pressure washer with a separate unloader that is not built into the pump.
Some good reasons to upgrade to a pump with an EXTERNAL UNLOADER:
External unloaders can be configured to have the bypass water return to a tank or to be dumped to the ground for the best possible cooling.
If you don't run off a tank or can't dump the water, external unloaders (aside from bolt-on banjo unloaders) will circulate more water outside of the pump for better cooling.
External unloaders can be replaced when worn out very easily and inexpensively without having to replace the pump.
Note On Internal Unloaders: Commercial pumps built with internal unloaders usually have replacement parts available. Unfortunately these repair kits can be expensive and are not a complete unloader replacement since the main body of the unloader is part of the pump head.