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Why a Pressure Washer Loses Pressure – Best 2023 Read!

Attachments, Buyers Guide, cleaning guide, electric pressure washers, FAQ, Gutters, Pressure Lose, Pressure Washer, pressure washers, Wands


A pressure washer is great; however, it is only helpful if it can produce and sustain the required pressure. The three main problems associated with pressure include; low pressure, complete loss of pressure and surging/pulsing pressure (where the pressure is good for a moment but then weakens).

Common reasons for pressure loss in a pressure washer are:

  • Insufficient inlet water supply
  • A blocked nozzle
  • A worn out nozzle
  • A clogged inlet water filter
  • A damaged unloader valve (can cause a complete lose of pressure)
  • A faulty pump
  • Trapped air
  • Obstructed nozzle
  • Blocked water inlet filter

Before you rush to call your mechanic, you can easily fix most of these issues. This article will discuss the reasons why your pressure washer losses pressure and look at how you can quickly troubleshoot them.

Why a pressure washer loses pressure

1. Inlet Water Supply

The most straightforward reason you might not be achieving the desired pressure is insufficient water supply. The amount of inlet water supply you require will depend on the type of pressure washer you have (commercial or residential).

For heavy-duty work, you might require a lot of water. However, a light-duty residential pressure washer will work with an average garden hose. This is because such hoses allow water to flow at a rate of 5-10 GPM (Gallon per minute). Most power washers have a GPM of 2.2 to 10.

Therefore, as long as your garden hose is working, it should be able to support your pressure washer. Check whether the inlet hose might have any leak or if the mains water supply is disrupted.

Also, ensure that water quality is good and does not contain algae, dirt, or sediments that might clog the nozzle or the pipes. If you are not sure about the quality of your water sauce, you can use filters to clean the water.

Fresh main supplied water should always be used. Avoid tank water.

Why a Pressure Washer Loses Pressure - Best 2023 Read!

A good water supply is essential to maintain a high pressure from your machine

2. Worn Out or Blocked Nozzle

The most common cause of low pressure is faulty nozzles. If your nozzle is worn out or blocked by any dirt/ debris, it will more than likely reduce the pressure of your washer.

Blocked Nozzle

If the nozzle is blocked, it might cause a significant drop in pressure or produce a pulsating/surging water spray. Nozzle blockage often occurs when you have not been using your power washer for a while, and dust accumulates. Luckily, unclogging the nozzle is very simple. Most modern washers come with a nozzle cleaner.

The first thing you need to do is to remove the nozzle. You can do this by turning it or pushing it downwards, depending on the type of power washer you have. Then you can use something like a piece of wire, bbq secure or similar to poke the nozzle from the front end, i.e. where the water sprays out.

This will push the debris backwards and allow the accumulated dirt to come out from the back of the nozzle.

Once you are confident that all the blockage has been removed, place the nozzle under running water to flush out any remaining dirt. Lastly, fix the nozzle back on the pressure washer gun and test to ensure it is functioning optimally.

Worn Out Nozzle

While nozzles can last you a very long time, they eventually wear out just like any other equipment. One sure way to tell if your nozzle is worn out is to check the pressure output.

If you detect a significant pressure drop, it is time to get a new one. A worn-out nozzle, in most case, can drop the pressure by up to 10% or more.

Some pressure washers come with spare nozzles. However, others don’t. If you have to buy a new one, always ensure that you choose the right one. The nozzle must be sized appropriately to be correctly paired with the pressure washer gun.

Putting a small nozzle can result in too much pressure, which can damage your property, e.g. your car’s paint. On the other hand, a large nozzle lowers the pressure, beating the whole purpose of replacing your old one.

Keep in mind that if you are going to purchase a replacement nozzle, they are not usually universal.

3. Blocked Inlet Water Filter

All pressure washers come with an inlet water filter that prevents debris from getting into them. This filter is usually located at the point where you connect your garden hose to your pressure washer. Depending on how severe the blockage is, the pressure might reduce, surge, or there might be no output.

Blockages can be severe as they can limit the amount of water being pumped. If the inlet filer is too dirty or clogged that no water reaches the pump, it can be a severe problem for your unit due to the lack of liquid to the pump.

If you suspect this might be the problem, remove the filter and rinse off the debris under running water. You can also use an old toothbrush to get rid of the debris. It is also advisable to regularly unclog your inlet filter to avoid future blockage.

If you notice your filter is damaged, replace it immediately. This is because dirt could get into your pump and cause worse problems.

Why a Pressure Washer Loses Pressure - Best 2023 Read!

Pressure washer inlet filters can get blocked and reduce your overall pressure

4. Damaged Unloader Valve or Incorrect Adjustments

The primary purpose of the unloader valve is to regulate the water pressure. That is why it is also called the pressure regulator. However, it also diverts the flow of water when the trigger of the pressure washer gun is not pressed. Another function is to relieve the water pressure when the spray nozzle is blocked.

If it is faulty, it will not be able to regulate the water pressure. This can either lead to too much pressure or loss of pressure. Additionally, suppose the unloader valve is not properly maintained or replaced when damaged.

In that case, it will not only lead to low pressure but can be a safety hazard and even damage your washer.

The most basic unloader valve issue is incorrect adjustments. To get the optimum pressure, you need to adjust the unloader valve to the right setting.

This will help you increase or decrease the pressure of your washer. To modify it, use the unloader valve knob located where the high-pressure hose connects to the pressure washer.

Always be careful when adjusting an unloader valve and always read the instructions. Here’s a few tips that should help:

  • Ensure that the washer is running at least 3400 rpm under the load
  • Squeeze the trigger and note the pressure. If it is too low, you will have to turn the valve knob clockwise and vice versa.
  • Before turning the knob, squeeze the trigger for a while and then release. Only turn the knob one turn at a time. You will have to repeat this ‘Trigger-Turn’ motion until you achieve the desired pressure.
  • When you achieve your desired pressure, allow the trigger gun to go off for a minimum of 15 to 20 times to prevent any hung up.

Always check the unloader valve if you’re having pressure problems

The unloader is located just above the water inlet. Always check to see if it is restricted in any way or if it is worn out. One way to determine if it is time to replace your unloader valve is to check if the nozzle on the trigger wand is worn. If that is the case, replace it and try to adjust the unloader valve.

If you do this and adjustments do not fix the issue, you have to repair or replace the unloader valve. Another sign that you need to replace the unloader valve is if it sticks open and constantly recirculates water back to the pump inlet.

5. Trapped Air

While most modern pressure washers are not prone to having air trapped inside them, older models that use suction mechanism often develop airlocks. However, non-suction pressure washers can also have this problem if you use loose fittings that are not airtight, for example, the hose or valve seals.

This trapped air can cause a loss of pressure, vibrations and pulsing pressure. If this air gets into the power pump, it can result in more damage. This is because it can cause little ‘mini explosions’ that damage the pump.

To fix this problem, you need to ‘bleed’ out the air. This is not that easy as you first have to establish where the air is entering the system. When you identify the spot, you can either tighten the part or replace it if it is worn out.

Once you are sure that no more air will be introduced to the system, disconnect the outlet hose from the gun and ensure the inlet connections are tight. Afterwards, turn the supply on, and the water will eventually push the air out. Keep the water flowing until you are confident there are no air bubbles left in the system.

6. Faulty Pump or Engine Problems

If you have checked all the above and your pressure washer is still malfunctioning. Then you might have a worn pump, or the engine might be faulty. Unfortunately, unless you are a qualified technician, there is really not much you can do to fix this problem.

The best thing to do is to protect either the pump or engine from premature wear. For instance, the pump is usually damaged by not changing the oil, using the wrong lubricant, or operating the pump with no water running through it.

One sure sign that you need a new pump is if your old one cannot maintain at least 1000 psi of pressure.

The engine also requires constant maintenance to operate optimally. Some practices that you should adopt include replacing the engine oil, checking the sparkplug, and cleaning the air filter.

In the case of faulty pumps or engine problems, we recommend you consult a technician. Nonetheless, if you properly maintain your washer, these are problems you will not have to deal with for a very long time.

Final Thoughts

If your pressure washer is not producing enough pressure, do not panic and rush to call your mechanic. Most of the causes for the pressure drop can be fixed with some simple adjustments. In most cases, loss of pressure is mainly caused by nozzle problems, unloader valve adjustments or blocked inlet filter.

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