Most Common Reasons for Experiencing Low Pressure and Troubleshooting Problems
Below we will be discussing several causes of low pressure most commonly appearing in conjunction with 3 other symptoms, pulsating, unsteady pressure, and steady, low pressure. We will start with the most common elements that fail and then lead into what components are difficult or easiest to check out.
Below we are referring to a cold-water pressure washer that is either tank fed or garden hose fed.
Pulsating Low Pressure - This can be felt as shaking or hard vibrating (also referred to as cavitations) when holding the spray gun while running the unit. Pulsating is usually associated with pump malfunction. It occurs when a cylinder misfires and results in a brief decrease in pressure.
First, check to see if there is damage to the pump’s head. If there is no visible damage, proceed to the following steps.
- Check to see that there is not debris blocking the valve. Inspect valves for deterioration.
- Check packings or seals for excessive wear.
- Check to ensure that piston or piston seals are not damaged. Leaking water from the crank case could easily indicated a damaged seal or valve.
* Note we skipped the rest of the machine and go straight to the pump in this case since this symptom is associated directly with the pumps pistons (plungers).
Unsteady Low Pressure - This is indicated by lower than normal pressure. The pressure may vary from slow to fast. Unsteady, Low Pressure usually signifies a problem with the water intake system (if the unit is tank fed.) This occurs when air enters the intake line.
First, check to see if there is an air leak. To detect an air leak, check the following components:
- Pump Inlet in Float Tank- Make certain that there is enough water in the feed tank so that the pump inlet is well below the water level.
- Ensure that your chemical injector is completely closed to prevent air from entering the intake line.
- Inspect the hose barbs to ensure that they are not cracked or weak. You can do this by giving them a firm shake. A damaged barb will bend or break.
- Examine all suction lines for cuts, cracks, abrasions, or heat damage.
If you have completed these 4 steps and still have not located the problem, you will need to pressure feed the suction lines to check for leaks. First, disconnect the feed line from the water tank and connect it to a garden hose. You do not need to run the machine, as the hose pressure is enough to reveal the leaks.
* After you turn the hose on, if there is water leaking from the pump crankcase the packing seals may be worn and need to be replaced. Water leaking from fittings indicates cracks or damage and may need to be replaced.
Steady Low Pressure - This is demonstrated when a machine is operating at a constant lower pressure than normal. Some possible culprits are pump starvation, loose belt drives, a clogged injector, or a badly worn tip.
- Pump Starvation (Tank Feed)- Check to ensure that the suction screen is not clogged. Pay special attention to make sure your intake lines are not obstructed or kinked. Pump Starvation (Garden Hose Fed)- Be sure that the garden hose spigot is producing adequate GPM. A damaged or kinked garden hose can also cause pump starvation. Check inlet filter and remove any obstructions. Inlet pressure regulator can malfunction or may be set too low.
- Loose Belt Drives- Check belt tension for slippage. If belt tension is off it can lower the RPMs that the pump is turning resulting in a lower operating pressure.
- High Pressure- If any leaks are occurring in the high pressure portion of the machine, it will contribute to pressure loss
- Wash Tip- Inspect wash tip for wear and tear. They need to be replaced often and can significantly reduce pressure. In addition, make sure you are using the correct orifice sized nozzles for your machine.
Inspecting the pump and unloader - After all the above has been checked and the problem still remains; we will turn to the pump/unloader to try and track down a solution to our low-pressure problems.
Unloader – While using your machine make sure that your unloader is functioning properly. It should move up and down and bypass the flow of water as you use or do not use the trigger gun. Also there is a quick check you can do to make sure the unloader is not bypassing unnecessary water. While depressing the trigger gun give the bypass hose a squeeze a feel for any unwanted water flow. If there is any water flow this could point to a malfunctioning unloader. *Please make sure the unloader is fully open to allow full pressure and flow.
Pressure Pump – The best way to check your pump and unloader is by separating the two. Remove the unloader, plug the bypass lines, and then connect your pressure hose directly to the pump. It is imperative that your trigger gun is fully depressed at all times when running this way. You may unwilling damage your pump otherwise. (Also be sure a pressure gauge is always attached to regulate the pressure output) If you are operating at normal pressure, your problem lies in the unloader. If the pressure is irregular have the pump serviced and then tested again.
Once your pump is operating at normal pressure reattach the unloader and make sure it functions properly as well.
* If you have a built in unloader this test cannot be performed.
Rapid Wear Out of Pump Internals – If your packings, seals, or other components are wearing out at a rapid rate you may be running the machine in bypass mode too long; running the pump dry can easily cause this rapid deterioration as well. Another cause can be running hot water through the pump itself. The seals and other components are not typically equipped for this unless otherwise stated in the pump specifications.
This basic overview of low pressure situations in cold water machines should help you deal with troubleshooting and resolving your problems with your pressure washer in the future.
Before trying any of these techniques described, be sure you understand what you are doing. If not seek the advice and help of an expert. There is a possibility and danger of equipment damage, shock, electrocution, burns, explosions, or fatal wounds can occur to you or a bystander without proper safety precautions and knowledge of the equipment. This material has been prepared as a guideline to help determine problems you are responsible for knowing exactly what you are doing. We are not help liable or responsible for any injuries or damage to equipment that is endured when trying these techniques.