Is It Bad To Leave A Pressure Washer Running Without Spraying?

While pressure washing, you may need to stop spraying to take a call or move a vehicle. This requires us to leave the pressure washer idling, which begs the question: is it bad to let a pressure washer run without spraying? 

Here is the short version:

Yes, letting your pressure washer idle for more than a minute or so will risk damage to your pressure washer’s pump. When you stop spraying, your machine runs in “bypass”, where your unloader cycles a small volume of water through your pump to prevent pressure buildup. This water will quickly heat up and damage sensitive components in your pump. Best practice is to try to always squeeze the trigger while your pump is running, but if you have to pause, keep it brief, and shut off your pressure washer if it will take more than a minute.

But there is a bit more to it than that. Here is what you need to know to keep your pump operating for years to come.

What are Unloaders, and How Do They Work?

Pressure washers work by pressurizing water (who would have guessed) for effective cleaning. When you let go of the trigger, your machine needs a way to release that built-up pressure to prevent damage to your pump.

That's where unloaders come in.

They work by redirecting water leaving your pump back into the inlet of your pump, a mode called "bypass." This recirculation prevents pressure buildup that would otherwise immediately cause damage since the pressure would otherwise have nowhere to go when you stop spraying.

Now, under normal operation, your pump is always fed fresh, cool water. In bypass, the pump recycles the same small amount of water in a closed loop, which due to friction from the pump’s operation, heats up quickly.

This is fine for a short time, but after a while in bypass, this water will heat up enough to damage the seals of your pump, usually rated for around 140°F. This can soften and potentially melt seals, which will lead to complete failure due to loss of pressure.

How Do I Safely Idle My Pressure Washer Without Damage?

In order to pause your cleaning process safely, follow these tips:

1. Minimize Time in Bypass: If you take one thing away from the article, it is this: If your pump is running, keep it spraying (as much as you can). You can pause if you need to, but keep time in bypass to a minimum.
2. Don’t Idle For Longer Than 60 Seconds: The amount of time it takes for water in bypass to heat up enough to damage your pump will depend on several factors, from ambient temperature, the length of your bypass hose, your specific pump, etc.

Because of this, there's no truly hard-and-fast rule for how long you can let your pump idle without damage. Our recommendation is to never idle your pressure washer for more than 60 seconds. If you can periodically cycle some fresh water through to keep it cool, you can extend this a bit, but in most cases, if you need to step away from cleaning, it's best practice to shut the pressure washer off.

1. Shut Your Engine Off: If you need to step away from cleaning, it is best to shut your engine off. A 60-second task can easily turn into a 5-minute side quest, which isn't worth burning out your pump over.

Other Ways To Protect Your Pump

• Lengthen Your Bypass Hose: One way to give your pump a break is to lengthen the bypass hose. You can do this by installing a longer hose, and looping it around a few times if necessary. The threat of overheating remains, but this buys you more time before the water gets too hot in bypass. 
• Buffer Tank Bypass: If you use a buffer tank, you can modify your setup to route the bypass water directly into the tank, rather than directly back into the pump. This effectively turns your entire buffer tank reservoir into your bypass, virtually eliminating the overheating issue due to such a small closed-loop system. 
• Bypass To The Ground: While less elegant than these other solutions, you can technically route your bypass hose to the ground, rather than back into the pump. This will waste water, but it is virtually the same setup as the tank bypass in terms of what your pump experiences.

However, this won't be a good option if you are using bleach upstream from your pump since this setup would cause you to dump it out. 

And there you have it! Unloaders make it possible to pause your cleaning task for a short time, but make sure to exercise caution if you want to get the most out of your equipment.

Speaking of, our part advisors are available to assist with your maintenance and upgrades. They know all the best parts and accessories to get the most out of your machine to tackle the specific cleaning challenges based on your region. Get in touch with one of our experts here!