Equipment Maintenance

Should I Adjust My Unloader to Adjust My Pressure?

Most everyday, we interact with industry contractors through a variety of media. From Facebook to Instagram to phone calls, text messages and DMs, we see and hear a good bit of information that is either incomplete or  incorrect.

Yesterday was no different. The original poster "OP" began the post with a question relating to the machine's chemical injector. Once that question was answered the OP wanted to know about the unloader and how to use it.

Let's dissect some of the incorrect information. My advice, training and knowledge comes from our associations with the manufacturers of the product along with in-field use. As vendors, we value the relationships we have with the product engineers. Who better to get product information from than the folks who design and build them?

So back to unloaders. Your machine's unloader is a valve. It is designed to open or close based on the pressure setting of the spring inside the unloader.  If you haven't looked at the inside of an unloader, it's main component is a coiled spring. Many of the unloaders have a black covering that hides the spring. But others like the green spring unloader, expose some of the inner workings.  The spring can be tightened or loosened to adjust the pressure at which the unloader (valve) engages and bypasses flow back to the pump inlet (or water tank).

Your unloader is important to your machine. Water under pressure needs a place to go. And if you aren't pulling your trigger gun and allowing that water to move, it has to go somewhere. If your machine has no unloader, and you are off the trigger gun, the water pressure will eventually blow apart the pump. This is a safety feature.

Let's talk about setting the unloader. Unloaders come in various designs - green spring, blue spring, black cover. Unloaders also come in various GPM and PSI ratings. This is important. Unloaders also come in trapped pressure relief and multi-gun styles. 

Typically, when we "set an unloader", we use a pressure gauge. With more experience, you can "hear" where it needs to be set. But if you don't know what you are listening or looking for, get a pressure gauge. Your goal is to find your "spike" pressure and set the unloader slightly above (100 - 300 PSI) that pressure or what we call the "pump head pressure". Assume that your machine is rated at 3500 PSI. Turn on your machine. When a pressure gauge is applied to machine, the spike pressure - the pressure your gauge reads when you let OFF the trigger - should be noted.  The pressure should also be noted when you are ON the trigger with water coming out the nozzle orifice. This is going to tell you where the tension rate (how tight the screw is on the spring) on the unloader should be set to allow the unit to function between the machine's rated 3500 PSI rating and the spike pressure. When you loosen the spring, it means the unloader will not engage until you reach a higher PSI. Tighten the spring, and the machine's unloader will engage at lower PSI ratings. It is SUPER IMPORTANT  to test with the PROPER orifice size nozzle. If your machine should have a 4.0 orifice, then test should be performed with a 4.0 orifice. This test may have to be repeated multiple times to achieve optimal results. 

The unloader is a mechanical device and it wears. By lowering the PSI at which the machine's unloader will engage, this causes the unloader to work much harder than it was designed and causes premature wear. 

Unfortunately, we see advice given routinely by keyboard warriors stating that the unloader can be used to lower the PSI. While that statement has some truth to it, the CORRECT way to truly lower the PSI is to use larger orifice nozzles (larger opening). This allows the machine and its components to function in the manner in which the engineers have designed it to work. 

Pressure wash systems have several components that need to work together. Adjust one component and it can affect another and so on and so on. 

Back in the late 90's infomercials were huge. And a guy named Ron Popeil created a company called Ronco. One of the best was the Showtime Rotisserie with his catch-phrase "set it and forget it". And that's exactly what you should do with your unloader. 

If you want a good laugh, take a look at the Ronco Showtime Rotisserie infomercial here.