Why isn’t my pressure washer building pressure? Helpful tips


A pressure washer works so well cleaning the exterior of your house because it uses much higher pressure than a regular hose. But still, a lot of pressure washer users complain about their pressure washer not giving the pressure they expect or used to provide. There can be many reasons for this problem. We have listened to the most common causes and how to diagnose and fix your pressure washer low pressure.

Why isn’t my pressure washer building pressure:

In general, the most common reason for a pressure washer not building pressure is that it is not getting enough water. This can be due to a hose problem, leakage, or blockage. Another reason can be air can get trapped inside the pressure washer pump or a problem with the nozzle. Less common is a problem with the pump or the engine.

Why isn't my pressure washer building pressure? Helpful tips 1

How to diagnose low pressure on a pressure washer?

To diagnose low pressure on a pressure washer, you first need to determine the type of pressure you are receiving. For pulsating low pressure, check the pump for any visible damage. For unsteady low pressure, examine the pump inlet for any air leakage and ensure that your water source supplies enough water. For steady low pressure, pump starvation and a loose belt could be the reason behind low pressure.

Below, we look at the different steps to diagnose the low water pressure in your pressure washer. Low water pressure can appear with different symptoms, like pulsating, steady, and unsteady low pressure. First, we will discuss each element one by one and then the components that you need to check to diagnose the cause of low pressure.

● Low pressure and Pulsating

Pulsating low pressure feels like a hard vibration of a spray gun during pressure washing, also known as cavitation. This pulsating low pressure mainly occurs due to a pump malfunction. The cylinder of your pump does not produce enough pressure and misfires, resulting in a decrease in pressure.

– Diagnose: Check the pump

You can diagnose the problem in the pump by first checking the head of the pump. If there is no visible damage, then check the valve of your machine for any dirt blockage. Also, check the inline filter because with time, dirt and debris gather inside the inline filter, and they increase to a significant level after a couple of washings. As a result, your pressure washer runs with very low pressure.

After clearing the dirt and debris from the pump valve, move towards the seals and check for any excessive wear. Then inspect the piston seals and if there is any water leakage. If there is, it means that your seals are damaged, which is the reason for the low pressure.

Unsteady low pressure

Unsteady low pressure is basically the water coming out of the nozzle with the pressure lower than normal. The pressure may also suddenly change from low to high. This unsteady low pressure can be due to some fault with the water intake system or when air gets trapped in the intake line.

– Diagnose: Check the pump inlet

In order to diagnose the reason behind this low water pressure, first, you need to check for any air leakage. To do this, make sure that your water source is supplying enough water for the pump inlet to be completely immersed below the water level. Also, ensure that there is no air entering the intake line from the chemical injector and that it is closed completely.

Check the hose points for any cracks by giving them a firm shake. Weak or cracked hose barbs will bend or break. Then inspect the suction lines for any cracks or heat damage. Finally, remove the feed line from the water source and attach it to the garden hose. The hose pressure will reveal any leaks, so you do not need to run the pressure washer.

Steady low pressure

Steady low pressure basically happens when a pressure washer is producing a lower pressure than usual. There can be many reasons behind this problem, and you can diagnose them by following the steps below mentioned.

– Diagnose: Pump starvation

Pump starvation is one of the main reasons behind low water pressure from the machine’s outlet. Ensure that the intake lines are not kinked or clogged and supply enough water to the pump. Also, if your hose is damaged, it will not produce enough GPM for the pressure washer to run at normal pressure.

– Diagnose: Loose belt

If the belt of your machine is loose or slipping, then it results in a decrease in the pressure of water. You can fix this problem by tightening or replacing the belt.

Why doesn’t my pressure washer have any pressure?

In general, a damaged pump, engine problem, and motor malfunction are the most common reasons behind your pressure washer having no pressure. Besides these problems, using hot water in a cold water pump or a loosened or damaged spark plug can also lead to no pressure in your pressure washer.

If your pressure washer produces low or minimum pressure, then it could mean that some components of your pressure washer are not working correctly. Instead of hiring an expert, you can troubleshoot your machine yourself.

Reason 1: Spark plug (gas pressure washer only)

If your pressure washer gas engine is running, but it does not sound ok. And it is not producing or only low pressure. First, check your machine’s spark plug. Examine the wires of the spark plug, and if they are loose, you can tighten them. Also, check if there is any corrosion at the edge of the plug. You can remove this corrosion using a brush, and if it is widely spread, then replace the plug.

Reason 2: Carburetor problem (gas pressure washer only)

If the sparkplug looks ok, but the engine does not run well, the carburetor could be the reason. If it is dirty, the engine will work less optimally, resulting in less or no pressure. If your engine is not throttling up, this is a clear sign. Disassemble the carburetor and clean it using carburetor cleaner. Ensure that you do not use bad gas. Bad gas is gas that has been stored for multiple months. Add fuel stabilizer if you plan not to use gas for an extended period.

Reason 3: Air filter (gas pressure washer only)

Another reason for the engine not working well is a dirty air filter. Remove the air filter and check it. If it is dirty, clean or replace it. A paper air filter needs to be replaced.

Reason 4: Hot water in a cold water pump

Another reason for the missing pressure in your pressure washer can be pump damage. There are pressure washers that can be used with cold water only. If these pressure washer pumps are exposed to hot water, it can damage the pump, which causes low pressure in your washer. If this is the case, probably replacing the pressure washer pump is the only solution.

Reason 5: Damaged pump

Sometimes using the wrong type of oil or lubricant or running the machine with old dirty oil can damage the pump of your pressure washer. You must check and change the oil of your pressure washer regularly. A gas engine has an oil filter to clean the oil when it is running. A pressure washer pump does not have it. So when the oil is dirty, it needs to be replaced. Some cheaper pressure washers are using a closed-loop pump oil system. For those machines, you can not replace the oil.

If you use your pressure washer without water, it will run hot. Water cools the pump. When running really hot, it can lead to a worn pump. In this case, you need to replace the pump.

Reason 6: Motor malfunction (electric pressure washer only)

In an electric pressure washer, the electric motor is the source that powers the pump works that generate the high water pressure. If your motor malfunctions, the pressure washer ends up losing pressure. To check that the motor of your electric pressure washer is working fine, push the trigger a couple of times. If your pressure washer produces high and low pressure, then your motor is fine.

How do you fix low pressure on a pressure washer?

The first step for fixing the low pressure of your pressure washer is changing its oil and cleaning the filter. If the pressure of your washer has still not increased, then check the water supply hose and adjust the unloader valve to your desired pressure. Many times the nozzle of the pressure washer is worn out, which causes low pressure. You can fix this problem by replacing the nozzle of your pressure washer.

Solution 1: Maintenance of your pressure washer 

The first solution to fixing the low pressure on your pressure washer is to maintain it properly. Each machine needs maintenance to make it last longer. This applies both to gas and electric pressure washers. Gas pressure washers require a lot more maintenance than their electric cousin.

To fix the low pressure of your washer, you should give proper attention to the maintenance of your engine and pump and for gas pressure washers also the engine. Check and change the oil at regular intervals. The filter of your pressure washer can catch a lot of dust particles during cleaning. This can result over time in lower pressure. Check and clean the inlet filter of your washer regularly. Also, check if the nozzle you use wear and tear. If you have an additional one, use that one and see if there is a difference.

Solution 2: Fixing the hose

If your pressure washer is still producing low pressure after checking and changing the oil, filters and cleaning the nozzle, the next step is to check the hose and the water supply going into the machine. Most pressure washers need at least a water supply of 0.9 gallons per minute.

According to most experts, the recommended diameter of the supply hose should be ¾ inches to maintain the correct pressure. If the washer’s pressure is still low with a ¾ inch diameter hose, check for any blockage in the hose. Disconnect the hose from the inlet valve, and check if the supply is sufficient. Also, remove dust and debris from the inside of the inlet filter.

Solution 3: Replace the nozzle

Another solution to fix low pressure is to replace the nozzle at the end of the trigger wand. Sometimes, the nozzle becomes worn and this results in a unusual spraying pattern of water. This worn out nozzle can also be the cause of the low pressure because of the holes in it that widen with time. As these holes widen, more water flows through the nozzle and decreases the pressure of the water. Nozzles will wear over time with regular use, and will need to be replaced. It is recommended that you have a number of nozzles on hand.  This allows you to easily change the nozzle if you see any decrease in pressure, and to test other nozzles to check if the pressure is decreased due to the nozzle or not.

Solution 4: Adjust the unloader valve

The main function of the unloader valve is to divert the water flow from the pump towards the bypass. This unloader valve can sometimes be the reason for low water pressure.

If replacing the nozzle did not make a difference, we have to check the unloader valve. Adjust it in small steps to increase the pressure of the pressure washer. To ensure a safe pressure, connect a pressure gauge when adjusting the unloader valve. During the unloader valve adjustment, ensure that the machine is running and pull the trigger to allow a flow of water through the machine. If adjusting did not help, the valve could be broken. In that case, it needs to be replaced.

Recent Posts