Why pressure washers lose pressure & what to do?

Approx Reading Time: 18 minutes

Pressure washing is a great way to wash large areas quickly and effectively. But one of the most common issues pressure washer owners run into is that the pressure washer unit loses pressure after some time. If the pressure washer is not spraying water with enough pressure it becomes difficult to remove dirt and clean a surface effectively. Some of the most common reasons why pressure washers lose pressure over time are:

  • The water supply hose is incompatible, damaged or the inlet filter is blocked
  • Worn out or blocked Nozzle
  • Water temperature is not compatible with the pressure washer unit
  • Problems with the engine itself
  • Incorrect adjustment of Unloader Valve
  • The air inside the pressure washer system
  •  Bad water pump

Luckily most of the above-mentioned causes of low pressure can be fixed relatively easily while a few of them might require professional help. Owning a pressure washer that is not producing as much pressure as you want or has a complete loss of pressure can be frustrating. Therefore, we are going to explain in detail the possible causes of pressure loss in the pressure washer and how you can overcome these causes.

Why pressure washers lose pressure & what to do? 1

Incompatible damaged or blocked water supply hose

It is no surprise that pressure washers require plenty of water in order to work properly and produce a steady stream of highly pressurized water. A decent-sized pressure washer unit needs around 4 liters of water every minute to run properly. In fact, the supply hose or inlet hose of a pressure washer is probably the first component to check if you are experiencing low pressure from your pressure washer.

Incompatible inlet/supply hose:

The diameter of a pressure washer supply hose matters a lot and you can’t expect to use the same diameter hose on every kind of pressure washer unit. If you use an inlet hose that is too narrow or too wide for the pressure washer it is going to provide an incorrect amount of water to the pressure washer unit and reduce the pressure of the unit.

Fix: Incompatible inlet/supply hose

The only way to solve the issue of an incompatible inlet hose is to get a new hose that is designed to be used with your pressure washer. You can refer to the user manual of your pressure washer to know the correct diameter inlet hose for your pressure washer. But if you don’t have the user manual for your pressure washer here are some general inlet hose diameters and their compatible pressure washer unit sizes:

1/4” Hoses: These hoses are considered the smallest diameter and they are mostly used with small pressure washer units designed for home use or small electric pressure washers. If you have a pressure washer with a pressure rating of up to 3200 psi then a ¼” hose is the one you should use.

5/16” Hoses: These are considered as mid-diameter hoses and they are suitable for pressure washers rated between 2700-3600 psi. But these hoses are rarely used and are not very common.

3/8” Hoses: These are the largest diameter hoses you can find in the market and they are meant to be used for commercial grade pressure washers. Not only are these hoses wide but they are also made with tougher materials and can be used for a pressure washer with up to 10,000 psi rating.

Why pressure washers lose pressure & what to do? 2

Damaged supply/inlet hose:

If the inlet hose of your pressure washer has any leaks or cracks in it then the water can leak and insufficient water will be supplied to the pump causing low water pressure. Since the pressure washer inlet hose has to withstand a lot of pressure it is not uncommon for an inlet hose to crack or break. If the damage is not too severe and the cracks are not spread all across the length of the supply hose you can repair the hose at home but if the cracks are too big it is best to get a new hose similar to the old one.

Fix: Damaged supply/inlet hose

You can use shears, a coupling kit with hose clamps and screwdriver to fix a crack or cut in the inlet hose. Once you have all the items ready you can follow these steps to repair the cracked or damaged inlet hose:

Step 1. Remove the hose from the tap and the pressure washer unit.

Step 2. Once you have spotted the crack you can cut the hose perpendicularly to remove the damaged section of the inlet hose using shears. Make the cuts at least half an inch on both sides of the crack.

Step 3. Now take the coupling kit with both male and female parts. But before fitting the ends of the hose on the male and female sides of the coupling kit you will have to put the hose clamps over the hose to secure both ends of the pipe on the coupling kit.

Step 4. Next insert the male coupling into one end of the hose that you just cut and insert the female coupling into the other.

Step 5. Tighten the hose clamps on both the male and female ends of the coupling kit to make sure the hose is held tightly onto the coupling kit. Use a screwdriver if needed.

Step 6. Finally, you will have to join both the male and female ends of the coupling kit together to finish the repair. And you can do it simply by turning both ends together until they are tight.

Blocked water inlet hose or clogged inlet filter:

If the source of water you have been using to feed water into the pressure washer is not clean it can cause the inlet filter to get blocked with debris. Inlet filter is usually located inside the point where the water supply hose connects to the pressure washer unit. Its job is to make sure no debris gets into the pressure washer pump and damage it. Besides the blocked inlet filter, there can also be a blockage inside the hose itself and both of these blockages can be fixed fairly easily.

Fix: Blocked water inlet hose or clogged inlet filter

If you notice that you have a blockage in the hose pipe itself due to the accumulation of debris in it then the best way to remove the blockage is to cut the section of the hose with the blockage using the same method that we explained above to repair the inlet hose. The inlet filter can even The cuts will have to be made in such a way that the blockage is removed along with the cut section of the supply hose and then you can rejoin both ends using a coupling kit. But when it comes to cleaning a blockage inlet filter you can do that by following these simple steps:

Step 1. Remove the inlet hose from the pressure washer inlet before removing the inlet filter.

Step 2. Turn the inlet nozzle on the pressure washer unit anticlockwise to take it off.

Step 3. Once you have removed the inlet nozzle that the water supply hose connects to, you can see the inlet filter inside. To remove the inlet filter from the pressure washer unit you can use pliers to pull it out.

Step 4. With the inlet filter removed, simply rinse off the debris under running tap water.

Step 5. Place the inlet filter back inside the inlet housing and fit the nozzle on the inlet filter housing before reconnecting the inlet hose.

Worn out or blocked nozzle

Another more common cause of low pressure in a pressure washer is a worn out or blocked nozzle which restricts the proper flow of water through it and therefore reduces the pressure of the pressure washer. So if you are experiencing loss of pressure or pulsating spray of water then a blocked nozzle might be the culprit. The hole of the nozzle is already pretty narrow and if the nozzle gets blocked you will experience a significant drop in pressure. Similarly, if the nozzle of the pressure washer has not been replaced for a long time it will wear out and the hole of the nozzle will become wider over time causing a drop in pressure.

Worn out nozzle:

Most people think that the nozzles of their pressure washer are meant to last forever. But depending on the quality of water, frequency of usage, and amount of pressure the nozzle is handling it will wear out quicker and therefore you will have to replace the nozzle sooner.

Fix: Worn out nozzle

While there is no specific duration after which you will have to replace your pressure washer nozzle, a good indicator that it is time to get a new nozzle for your pressure washer is if there is more than a 10% drop in pressure. Every pressure washer has a pressure gauge that tells you about the operating pressure of the unit. And you will have to remember the operating pressure of the pressure washer when you bought it brand new to know if the pressure has dropped more than 10% or not.

Note: Since there are other causes of loss of pressure in a pressure washer it is a good idea to rule out other possible causes of a drop in pressure before you replace the nozzle. But normally replacing the worn-out nozzle of the pressure washer should resolve the low-pressure issue.

Blocked nozzle:

If you haven’t been using your pressure washer very often or if the nozzle of your pressure washer is not too old then the cause of low pressure can be a blocked nozzle. Especially if the spray of water seems to be pulsating or irregular along with low pressure. Luckily unblocking or unclogging a nozzle is a relatively simple task and you can give it a try before replacing the nozzle because sometimes a nozzle is simply clogged and not worn out.

Fix: Blocked nozzle

You can unblock a pressure washer nozzle with these simple steps:

Step 1. The nozzle has to be removed in order to clean it because trying to clean the nozzle without removing it is only going to cause the debris to go back inside the nozzle. So to remove the nozzle you will have to turn off the pressure washer unit and squeeze the handle a few times to remove any pressure inside the nozzle.

Step 2. Remove the nozzle from the pressure washer gun by either turning or simply pushing the nozzle downwards depending on the type of pressure washer you own.

Step 3. You can either use the nozzle cleaner that came with the pressure washer or you can use a straightened paper clip. But it is recommended to use the designated nozzle cleaner to avoid any damage to the nozzle. Poke the nozzle from the front end ( where the water sprays out).

Step 4. Push the blockage backward so that it comes out from the back of the nozzle.

Step 5. Once you are sure that the blockage has been loosened up, place it under running water preferably pressurized water so that any loose debris can be flushed out from the nozzle.

Step 6. Place the nozzle back on the pressure washer gun and test to make sure the pressure is optimal.

Incompatible water temperature

There are two types of pressure washers, hot water pressure washers, and cold water pressure washers. And both of them can only run properly when the correct water temperature is fed into them. If you are using incorrect water temperature in your pressure washer then your pressure washer will not be able to provide optimal water pressure. Not to mention that the pressure washer pump can get damaged if wrong temperature water is used in it. You can’t simply convert a hot water pressure washer into a cold water one and vice versa.  

Fix: Incompatible water temperature

Refer to the user manual of your pressure washer to know if it is a hot water or a cold water one. Once you have determined the correct water temperature for your pressure washer make sure you are feeding the correct water temperature to your pressure washer.

Engine problems

Gas-powered pressure washers provide the most power because they are powered by a gasoline engine. And just like any engine, a pressure washer engine requires regular maintenance to produce the optimal amount of power. But if a pressure washer engine is not being maintained regularly it won’t be able to perform properly and this results in a drop in pressure. From the fluids to the air filter of the pressure washer there are quite of few items in the maintenance checklist of your pressure washer engine. And it is important to take proper care of your pressure washer engine if you want to enjoy high-pressure cleaning. A telltale sign of a bad pressure washer other than low water pressure is stalling, engine running rough or suddenly shutting down. Sometimes a gasoline pressure washer might even fail to start at all which is also an indicator of an engine problem.

Fix: Engine problems

If you want to get the maximum pressure from your gasoline-powered pressure washer and get rid of low pressure you have to keep the engine in perfect condition. Some of the most common engine maintenance you can do to increase its output is:

  • Keep an eye on engine oil: Engine oil is an important fluid for the engine of your pressure washer because it keeps the engine running smoothly by reducing friction between the internal components of the engine. If you have been using the same engine oil for more than 200 hours, the oil will lose its ability to lubricate the engine, therefore, reducing pressure. So it is very important to check the engine oil level every time you use the pressure washer and change the oil when needed.
  • Check the sparkplug: A bad sparkplug will cause the engine to lose power and run improperly and even shut off completely. So if you notice misfires from your pressure washer engine and the fuel consumption is also higher than usual with an obvious loss of water pressure it is a good idea to check the sparkplug of your pressure washer engine. Remove the sparkplug and look for any cracks or signs of damage or being burnt completely. If you notice any of these signs, it is time to replace the sparkplug to get the proper water pressure out of your unit.
  • Check the air filter: Air filter does exactly what its name suggests. An air filter’s job is to provide clean air to the engine of the pressure washer and allow it to run properly. But if the air filter is not clean or it is damaged you will start to experience lower power pressure from the pressure washer because of unclean air coming into the engine. So to check the air filter, open up the air filter housing and check if the filter is dirty or damaged in any way. In case of a reusable foam filter, you can clean it and put it back inside the air filter housing. But if your pressure washer has a paper air filter you will have to get a new air filter if the old one seems dirty and worn out.

Incorrect adjustment of the unloader valve

The unloader valve is responsible for diverting the flow of water when the trigger of the pressure washer gun is not pressed. When you release the trigger the unloader valve sends the water back to the inlet of the pump, therefore, stopping the flow of water to the nozzle. But apart from stopping the flow of water unloader valve can also affect the pressure of water that comes out of your pressure washer nozzle. If the adjustments on an unloader valve are incorrect you will not be able to get the pressure you require.

Fix: Incorrect adjustment of the unloader valve

You can adjust the unloader valve using the unloader valve knob that is located where the high-pressure hose is attached to the pressure washer. Remember that adjusting an unloader valve is a very delicate task and you should pay extra attention when adjusting the unloader valve:

Step 1. Run the pressure washer, at least 3400 rpm under the load with water flowing through it.

Step 2. Now squeeze the trigger of the pressure washer gun and note the pressure that is shown in the pressure gauge. If the pressure on the pressure gauge reads low you will have to turn the unloader valve knob clockwise to increase the pressure.

Step 3. Squeeze the trigger again for a while and then release the trigger and start adjusting the unloader valve knob one turn at a time. Squeeze the trigger again and release it then turn the knob again you will have to repeat the process until the pressure reaches your desired level.

Step 4. Make sure that when you release the trigger the pressure gauge doesn’t increase more than 300psi above the pressure when the trigger is pulled and water is spraying.  

The air inside the pressure washer system

If your pressure washer system has air trapped inside of it you are going to experience a loss of pressure, vibrations and sudden drop and increases in water pressure. Pressure washers with a suction mechanism for sucking water into the pump are more common to get air trapped in them. But none suction pressure washers can also get air in them and lose their pressure. The main cause of air entering in the pressure washer system is loose fittings. If a hose or fitting is not airtight, air can get into the system very easily and reduce the pressure. Since pressure washers are meant to work in a closed system, even a tiny space can cause air to get into the system.

Fix: The air inside the pressure washer system

Inspect the hoses and joints to make sure there is no damage to the hoses and the fittings are airtight. If you replace the hoses or fittings make sure you replace them with correct sized hoses and fittings to avoid getting vacuum leaks and prevent air from getting into the system. Once you have identified and taken care of the cause of air getting into the system you can then remove the existing air from the pressure washer using the steps explained below:

Step 1. Connect the inlet hose with the pressure washer.

Step 2. Turn the water tap on to allow water to flow into the pressure washer without turning the pressure washer motor on.

Step 3.  Press the trigger of the pressure washer to allow water to flow through the system with the pump and engine off.

Step 4. Keep the water flowing through the pressure washer for a few seconds until you are sure there are no bubbles of air left in the system.

Bad or worn out pressure washer water pump

The pump of the pressure washer is what actually pressurizes the water coming into the pressure washer unit. Your pressure washer pump may become weak because of improper usage and can even fail, causing a loss of pressure and even no pressure at all. A pressure washer pump can go bad due to either lack of proper water supply or due to being in by-pass or standby for long periods. By-pass is a situation when the pressure washer is running but the trigger has not been pressed.

Fix: Bad or worn out pressure washer water pump

If your pressure washer is not able to maintain even a 1000 psi of pressure then it is a clear indicator that you need a new pressure washer pump. One thing to make sure when replacing a pressure washer pump is to get the right replacement pump for your pressure washer. Avoid installing a pump with a higher PSI than your pressure washer engine is rated for because your engine will not be able to run a pump if it is above its recommended psi range. It is best to get a professional to replace the pressure washer pump for you to avoid running into any issues and damaging other components. Make sure that the shape and size of the replacement pump are the same as the pump you are replacing for a perfect fit.

Conclusion

 All of the above-mentioned causes of low pressure should be investigated one by one because the loss of pressure might be caused by either one or due to multiple reasons. While most of the issues mentioned in this article can be fixed very easily other items such as replacing a pump can be costly and difficult at the same time. Therefore if you want to avoid damaging your pressure washer pump it is best to turn the pressure washer off when you are done cleaning instead of letting it by-pass for long periods. Also, connect the water supply hose first before running the pressure washer to avoid causing air to get into the system. With a little care, you can prevent your pressure washer from losing pressure in the first place.