Pump Troubleshooting

By Dan Galvin / Published April 2022

The two most common pump problems operators say they have are “low pressure” or “no pressure.” Actually, the pump is the most durable part of your pressure washer. In my experience, usually what people think is a pump failure or problem isn’t caused by the pump at all. 

     While there are multiple possibilities why each of the following problems can exist, here are the most common. For accurate troubleshooting you’ll need to have a pressure gauge on hand. 

Low Pressure

     Low pressure is usually not a result of a pump malfunction. Often it’s a water supply issue, and occasionally it’s the unloader. To start troubleshooting, you’ll need to observe what your equipment is doing. When you open the trigger gun and your water is flowing, what does your pressure gauge say? Let’s say your pressure gauge is reading 2000 PSI, and you normally run at 3500 PSI. When you release the trigger gun, does the pressure go up before the unloader goes into the bypass? If so, that means the pump and the unloader are working and that you have a water supply problem. 

Is Your Water Flow Smooth or Pulsating?   

     Observe spray patterns to identify potential problems. Is the spray coming out of the high-pressure nozzle smoothly or pulsating like it’s missing a cylinder? 

If the Water Flow Is Smooth, Is the Hose Vibrating?

     If the answer is a “yes,” this occurs when there’s an air leak in the supply line to the pump. Imagine putting a hole in the top of a straw and then trying to drink with it. No matter how much you try, you’ll never get adequate suction. That’s what is happening when you have an air leak. Check for a loose hose clamp or a pinhole[s] in the hose. 

     If the hose isn’t vibrating, you most likely have a water supply problem. Does the pump make a loud screeching sound? If so, it’s due to insufficient water flow. Always look for the obvious solutions first. In this case, check for a kinked or pinched hose or a clogged filter. If that’s not an issue, it’s time to consider how the water is getting to the pump and from what type of water source. 

     Do an equipment check. Are you using the correct size supply line? A large diameter supply line helps water flow. However, if it’s too large, the weight of the water will be too much for the pump to draw. Also, keep in mind that the longer the supply line is, the lower the water flow will be.

     Once you’ve determined your supply line is appropriate for the job, then you’ll want to make sure the water supply can keep up with the demand of the pump. If the machine is fed by a direct hook-up to a domestic or city water source, run a test to determine the gallons per minute the water source produces. You can do this by running water from the hose into two five-gallon pails for 60 seconds. The water source should produce at least one gallon more per minute than the pump is rated for; if not, you’ll need to find an additional water source. 

     It’s also possible with a city water supply to over-pressurize the high-pressure pump. If this is happening, use a pressure-reducing valve on the supply line. If the machine has a float tank, be sure the supply line between the float tank and the pump is large enough to produce sufficient flow. The higher the gallon per minute rating of the pump, the larger the hose diameter must be. Don’t be mistaken and think that a float tank is a buffer that will allow you to connect to a low-flow water source. The small capacity of a float tank will provide only a few seconds of running time before running dry. A machine that’s supplied by a water tank needs a supply line with a larger diameter. The exact size required depends on the pump rating. 

In Case of Choppy Waters

     Is the water flow pulsating like it’s missing a cylinder? If so, it probably is. There are six check valves on the pump head—three on the top and three on the bottom. Look to see if one of the top valves is stuck in the open position. To do this with the power off, remove the valve and hold the retainer (plastic piece) in your hand. After you’ve rinsed and cleaned the check valve, test it by putting the stainless end to your lips. If the valve is operating correctly, you should be able to blow out through the valve, but you shouldn’t be able to suck the air back through it. If you can suck air back through it, the valve isn’t operating correctly. If that’s the case, look for any debris that could be keeping the valve open. Even a grain of sand can stop it from working. In most cases, the issue is occurring in the top valves. 

     If the top three valves are working, repeat the process for the bottom three. If the bottom valves are working, the problem is most likely internal to the pump and will require professional repair. If the valves aren’t working, follow the procedure described above to check for stuck valves.

No Water Pressure

     If there is no water pressure, check your unloader bypass to see if water is going through. If it is, the pump is working, and the problem is elsewhere. Make sure your nozzle is not clogged and the trigger gun is working. If both the nozzle and the trigger gun are working, check for debris in your unloader. To flush out the unloader, loosen the spring as far as you can. Then with the pressure washer running and the trigger gun open, start to tighten the spring on the unloader. Doing this should remove any debris. 

     No water pressure can also be a result of equipment wear and tear. Unloaders are power washing work-horses—because this piece of equipment is a high-use and high-wear item, you should plan on replacing it every year. It’s a best practice to always have a backup unloader in your inventory. 

No Water Coming Out

     You’ve turned on the water supply and you’ve checked for clogged filters and there are no kinks in the hose. Now what? With a good water supply established, inspect the lower three check valves in the pump head. In some pumps, if one of the lower check valves is stuck open, the pump won’t work. Occasionally, in brand new pumps the check valves are stuck closed. If you inspect and find the valves closed, follow the instructions explained earlier for checking valves. 

Preventive Maintenance

     Remember, the best form of troubleshooting is preventing problems from occurring with regular equipment maintenance. While there’s a chance of catastrophic failure in your pressure washer, most often the problem is an affordable, easy fix. The pump troubleshooting actions we’ve covered here should be enough to help you PowerThrough!™ and get you back in business. 

     Dan Galvin is EnviroSpec’s president and CEO and has worked in the power washing industry for 20 years. If you have more questions for Dan, contact him at (800) 346-4876 or visit www.envirospec.com.