How to Fix a Karcher Pressure Washer That's Leaking

If your Karcher pressure washer is leaking in some way, you'll be relieved to hear that you can fix the problem at home by yourself. All you need to do is figure out where your Karcher is leaking from leaking and why. That's where we step in to help!

In this article, written by an in-house eSpares repair expert, we run through all the possible reasons why your Karcher might be leaking water, or even soap. We also explain how to fix all of these leaks step-by-step, so let's get stuck in!

Where and why is my Karcher pressure washer leaking water or soap?

There are a few possible places your Karcher could be leaking from. These include:

• Your Karcher pressure washer leaking water from the bottom
• Your Karcher pressure washer leaking water at the hose connection at the back
• Your Karcher pressure washer leaking water from the lance or dirtblaster
• Your Karcher pressure washer is leaking soap

And more! Fortunately, as mentioned, any and all leaks can be fixed without needing to replace your pressure washer or call a repair professional.

What you will need

To fix a leaking pressure washer, there are a range of tools you might need, depending where the leak is coming from. These tools are:

• Torx T15 screwdriver
• Torx T25 screwdriver
• Small flatblade screwdriver
• Pin nose pliers
• H6 socket or a Torx T40 screwdriver (either one will work)
• Karcher O ring seals

If you need to buy any new rubber O ring seals for your Karcher pressure washer during this process, remember to make sure you get the correct ones for your particular make and model of appliance. If you're not sure what make or model your appliance is, our model number finder page is here to help!

Safety Advice

Remember, always make sure an appliance is switched off and unplugged from the mains (if applicable) before carrying out any work.

Also, please note that we're using a Karcher K4 model for this guide. If you own a different model of Karcher pressure washer, there's a chance that this process may differ slightly.

Fixing leaks from a Karcher pressure washer step-by-step

Let's dive in! To learn how to fix any and all leaks coming from your Karcher pressure washer, either watch our video tutorial below or follow our written step-by-step guide beneath.

In the video above, one of our presenters runs through every possible leak your Karcher pressure washer might be experiencing and shows you how to fix them.

Water leaking from the bottom

First, we'll cover how to fix your Karcher pressure washer if it's leaking from the bottom. If there's water on the floor around your appliance, this means the leak is likely coming from the main water inlet hose connection near the bottom of the pressure washer. First, make sure this connection is screwed on tightly all the way. If the connection was loose, tightening it may fix the leak.

However, if the connection was already tight - or if tightening it didn't stop the leak - you will need to check the rubber O ring seal inside. To check this, unscrew the water inlet hose connection from the pressure washer and look inside the connection. There should be a small rubber seal here. If there's no seal here, this will be the cause of the leak. Therefore, you will need to buy a new Karcher O ring seal to put inside the connection.

Alternatively, if there is a seal but your pressure washer is still leaking from this location, it means the seal is dirty or damaged and ineffective as a result. Remove the seal and inspect it. If it's just dirty, simply give it a good clean before refitting it back inside the connection. However, if the seal is damaged, you will need to buy a new seal and fit it inside the connection in place of the old seal.

When refitting the inlet connection back onto the pressure washer, make sure you tightly screw it back on all the way. If this is loose and not screwed on properly, this will cause water to leak out.

Water leaking from the hose connection at the back

Is your Karcher leaking water from the hose connection at the back of the pressure washer? If so, it means the Karcher hose isn't connected properly, so you will need to make sure it's connected in the correct way.

The main thing to note here is that, when fitting your hose, you need to slot it into the rear connection before clipping it into place. Otherwise, if you incorrectly try to slot the hose into the connection with the clip already fitted (as pictured below) the hose won't go all the way in - even though it will seem like it has. This incorrect fitting will cause water to leak out.

To correctly fit the hose, make sure the clip is not in place - and remove the clip from the connection if it is.

With the clip removed, take a look at the connection end of the hose. You will see that the connection has two flat sides.

Then look at the connection at the back of the pressure washer. You will see two flat sides (one on either side of the opening).

When fitting the hose, make sure the flat sides on both connections align properly. This will allow you to slot the hose connection all the way into the back connection until it clicks into place.

Then, once the hose is slotted into the connection, secure it by fitting the clip into place. Remember, this clip is essential. Without it, the connection will still leak water, and the hose will likely blow out next time you try to use the pressure washer.

Water leaking from the lance or dirtblaster

Now let's take a look at how to fix your pressure washer if it's leaking from the Karcher lance or Karcher dirtblaster. If you're using one of these tools and water is leaking from where the gun connects, it means there's a problem with the rubber O ring seal with whichever tool you're using.

To check the seal in either tool, first use a 50p coin to unscrew the yellow stopper at the end. This will just be a small twist, and the stopper will stay inside the tool at first.

Once unscrewed, use a flatblade screwdriver to pry the stopper out of the tool.

With the stopper removed, you will be able to see the small rubber O ring seal inside. This will be the same on both the lance and the dirtblaster. To stop your pressure washer from leaking here, you will simply need to replace the seal with a new Karcher O ring seal.

Disassemble your pressure washer to check for internal leaks

If your pressure washer isn't leaking from any of the above locations but is instead leaking from inside, you will need to disassemble your pressure washer to access and fix the cause of the leak.

First, unscrew and remove the small black water inlet hose connection located at the bottom of the front of the pressure washer.

Next, using your Torx T15 screwdriver, you will need to unscrew the eight screws that keep the front casing connected. Of these eight screws, six are located at the back of the pressure washer, with three on either side (leading down from just below the top handle to just above the wheels).

With these six screws removed, you will then need to unscrew the last two screws from the underside of the pressure washer (one on either side between the Karcher wheels).

Then you will need to remove the tool carrier. To do this, remove the two small black lugs that are located on the underside of the pressure washer. These lugs hold the tool carrier in place.

First, use your small flatblade screwdriver to carefully pry each lug out a little bit. You won't be able to use the screwdriver to fully remove the lugs - you just need to wedge the screwdriver blade underneath and loosen them enough to be able to grip the circular end with your pin nose pliers.

Once the lugs have been pulled out a little, use your pin nose pliers to work the lugs all the way out. The lugs will be quite stiff, so take your time and be careful not to damage them with your pliers as you remove them.

With the two lugs removed, you will be able to remove the tool carrier.

After removing the eight screws earlier, you will now be able to lift the front casing a little way off the pressure washer. Holding the casing on either side, carefully wiggle it free of the water inlet valve inside, and lift it up a little.

You won't be able to fully lift the casing as it will still be connected on the inside by the Karcher soap dispenser hose and the mains cable. To fully free the casing, first reach inside and pull the soap dispenser hose out of its inner clip.

Then also remove the mains cable from the inner clip that holds it in place.

Now, returning to the soap dispenser hose, you will need to pull off the end that's connected to the small soap feed pipe. This is the pipe that's on the pump housing, at the top of the Karcher motor inside the pressure washer.

You will now be able to lift away the front casing. At this stage, you will need to remove the Karcher control knob from the casing. To do this, just squeeze in the three small black clips that keep the knob held into place...

Then pull the control knob out of the front of the casing.

Soap leaking from your pressure washer

Now that you have access to the inside of your Karcher pressure washer, let's look at all the possible causes of interior leaks. First, we'll address how to fix your appliance if it's leaking soap instead of water, as there's only one place this can come from - the Karcher detergent dispenser bottle hose. Soap will leak from here if the hose isn't properly connected to the soap feed pipes on either end. So, to fix this, simply make sure this small hose is securely connected on both ends.

Water leaking from the top of the water outlet

Next, we'll look at how to fix leaks from the top of the water outlet. To access this area properly, you will first need to disconnect the end of the detergent dispenser hose that's connected to the Karcher pump at the top of the motor inside the pressure washer.

The outer casing will now be fully disconnected, so you can place it aside to access the inside of your pressure washer more easily. At this point, we recommend wearing some safety gloves to keep your hands protected whilst handling the internal parts of your appliance.

At this point, you might find that your Karcher pressure washer is leaking from the top of the water outlet (as pictured below). To fix this, you will first need to remove the motor from the inside of the pressure washer.

To remove the motor, use a flatblade screwdriver to pry out and remove the clip that holds the motor unit in place at the top.

Now you can go ahead and remove the motor. You will need a second person to help you do this. With one person firmly holding the pressure washer's main body, the other person will need to grab hold of the motor and work it off the pump housing (which is where the motor is connected at the top).

Once worked off the pump housing, the motor can be removed and stood upright.

With the motor removed and placed aside, go back and inspect the internal pressure washer connection you removed the clip from a few moments ago - this is the connection that the motor unit was connected to. If there is no O ring seal inside here, or if there is one but it's damaged, you will need to replace it with a new Karcher O ring seal. If there is an O ring seal in place inside this connection and it isn't damaged, you can move onto the next step.

Check the three remaining internal areas for leaks

At this point, there are three possible areas your pressure washer might be leaking water from inside. The first is the pump cylinder head, which is positioned at the top of the pump above the motor.

The other two areas include the pump feed pipe, which protrudes from the side of the pump and is pointing down by the side of the motor...

And the water inlet pipe at the bottom of the motor.

You will know which area is leaking depending on where there is water coming from inside your appliance. If water has sprayed up at the top, it means the pump cylinder head is the cause of the leak. However, if water has leaked down at the bottom inside the pressure washer, it means the pump feed pipe and water inlet pipe will need checking instead.

Water spraying up at the top from the pump cylinder head

If water has sprayed up at the top, as mentioned above, it means the leak is coming from the pump cylinder head. In this case, you will need to look inside the top of the pump cylinder head.

Inside the top tube (pictured below) there should be a small rubber seal. So, if your pump/cylinder head has leaked/sprayed up from here, it's likely that there's either not a seal where there should be one, or there is a seal but it's damaged. Either way, you will need to fit a new Karcher O ring seal here to fix the leak.

Water leaking down at the bottom inside the pressure washer

If water has leaked down at the bottom inside the pressure washer instead, the pump feed pipe and water inlet pipe will both need checking - as mentioned above.

To check these pipes, you will first need to slightly loosen the four bolts on top of the pump using your H6 socket or Torx T40 screwdriver (either one will work).

Then use your flatblade screwdriver to work out the metal circlip at the top. Once you've worked the clip a little way out with your screwdriver, you can pull it all the way out by hand and place it aside.

Once the clip is out, you can pull the pump feed pipe away from the pump/motor unit at the top...

Twist the pump feed pipe to the side, as pictured below...

And then pull it up and out to remove it.

Place the pump feed pipe aside and look inside the pump cylinder head opening on the pump itself - not the pipe. Inside this opening (where the larger upper end of the pipe was attached) there should be a small rubber O ring seal. However, if your pressure washer was leaking here, it means there either isn't a seal or the one that's there is damaged. Either way, you will need to fit a new Karcher rubber O ring seal here.

Then check the thinner bottom side of the actual pump feed pipe. As pictured below, there should also be a rubber O ring seal here. If this is missing or damaged, you will need to replace it.

Once you've checked and replaced these seals, you can refit the pump feed pipe. To do this, slot the thinner bottom side into the hole on the motor unit and push it down as far as it will go.

Then twist it into place and push the larger top end firmly into the pump cylinder head opening.

Make sure you also secure the pipe by pushing the metal circlip back into place...

And make sure you also retighten the four bolts at the top that you loosened earlier.

Now, you will also need to check the water inlet pipe to make sure your pressure washer isn't leaking from here too. To inspect this pipe, you will first need to unscrew it from the bottom of the motor unit. To do this, use your Torx T25 screwdriver to remove the two screws that hold it onto the motor (one above and one below).

Once unscrewed, pull the water inlet pipe off the motor and inspect the seal on the end that was connected to the motor. Again, if this seal is missing or worn/damaged, you will need to replace it with a new Karcher rubber O ring seal.

Once you've checked and replaced the seal, you can screw the water inlet pipe back onto the motor with your Torx T25 screwdriver.

Reassemble the pressure washer

Once you have checked for internal leaks and carried out the necessary fixes, you will need to reassemble your pressure washer. Start by fitting the motor back into the pressure washer - you will need a second person to help you do this. With one person holding the pressure washer, the other person will need to work the motor and pump onto the pump housing at the top.

Then slot the metal clip back into place on the pump housing above the motor. This clip will keep the motor and pump unit securely connected to the pump housing.

Now you can begin reconnecting the front casing, starting by refitting the soap dispenser hose and mains cable inside. First, reattach the end of the soap dispenser hose onto the small soap feed pipe above the motor.

Then reconnect the mains cable to its clip inside the casing.

You can then go back to the soap dispenser hose and clip it back onto the small inner clip.

You can now slot the front casing onto the pressure washer. There are a few things to note when you do this. First, make sure the two black tabs at the bottom of the pressure washer go outside the casing. Otherwise, if they're inside, the casing won't fit properly.

Also, on one side, you will need to align the mains cable with the indent on the side of the pressure washer (as pictured below) to ensure it doesn't get trapped between the casing and the pressure washer...

And, on the other side, you will also need to align the water outlet with the hole there for the same reason.

With all this accounted for, you will be able to slot the front casing into place on the pressure washer.

With the casing in place, secure it by refitting the eight screws you removed earlier using your Torx T15 screwdriver. These are the six screws at the back...

And the two screws on the underside of the pressure washer.

Now you can refit the tool carrier. First, slot the carrier into place on the front of the pressure washer at the bottom.

Then push the two black lugs back into place at the bottom of the pressure washer. Make sure you align the flat sides of the lug circles with the black ridges on either side of the openings, ensuring they can slot all the way into place.

Next, you can refit the control knob. You will be able to see the control switch through the control knob opening.

Make sure this is lined up with the slot on the inside of the control knob.

With this lined up, you can simply push the control knob back into place in the opening over the control switch.

Finally, screw the small black water inlet hose connection into place at the bottom of the front of the pressure washer. Once you've done this, your pressure washer will be fully reassembled.

How to find the right rubber O ring seals for your Karcher pressure washer at eSpares

By fixing leaks in your Karcher pressure washer by yourself, you don't only save money by avoiding calling a repair professional - you also save yourself from having to buy a whole new appliance needlessly!

Here at eSpares, we have everything you need to fix every leak yourself. Alongside this guide, we also have the Karcher rubber O ring seals you might need to fix many of the possible leaks on our online shop. Plus, if you're struggling to know exactly which seals to buy, we're here to help you find the right ones!

Does your Karcher pressure washer have everything it needs?

Now that your pressure washer is up and running again, ask yourself... do you have everything you need to get the best results? If you're not sure, we've got you covered with our wide range of pressure washer cleaning detergents to help you clean every surface and outdoor area of your home!

Finally, don't forget that eSpares is also here to help you fix any other problems or faults your pressure washer might run into. Alongside our library of pressure washer repair guides on fixing common issues step-by-step, we also have a huge range of affordable pressure washer parts and accessories to help you get the job done at home - and save while you do it. It's easy with eSpares!