How to clear a blocked pressure system

blocked pressure system A blocked pressure system on a washing machine can result in various different symptoms. But it’s not something to speculatively do in the hope that it will fix a fault. The pressure system isn’t always easy to get to – and all symptoms have other potential causes too.

Here is a list of common symptoms of a blocked pressure system –

  1. Washing machine won’t go into a fast spin. After a few minutes of successfully draining the water there is a click and the machine stops. Sometimes it might just switch off having not done the fast spin
  2. Washing machine overfills
  3. It produces an error code during the rinse cycle
  4. It won’t take in water and starts washing with no water inside (may energise the heater!)

Remember that all of these symptoms can also be caused by various different faults unrelated to the pressure system. The first one for example could be also caused by something as simple as an unbalanced load (won’t spin just one item or very small load).

To properly diagnose and understand if there is a blockage you need to carefully read and understand how the pressure system in a washing machine works – How a washing machine controls water levels | Faults on pressure system.

The most common symptom of a blockage in the pressure system is the first one in the list. But if it won’t kick into the fast spin there are more likely causes such as if it hasn’t drained the water out (water isn’t pumping out). It’s important to understand that a blockage in the pressure system will not stop water being pumped out. The problem is that the water has pumped away but the blockage prevents the signal that it has gone from being activated. The washing machine won’t do the fast spin if it thinks the water has failed to pump out.

Did you hear the water pumping away OK as normal? Unless sure, call an engineer


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Testing for a blocked pressure system

pressure tubing There is a quick test that may indicate a blockage. Once all the water has been pumped away and the washing machine has refused to spin or cut out, disconnect it from the mains power. Then take off the lid. With the washing machine totally disconnected from the mains carefully twist and pull the small rubber pressure tubing away from the pressure switch. If you hear a click when the tube comes off this is the pressure switch turning off as the trapped air is released.

Now try gently blowing down the tube. Is there any resistance? If you can’t blow down the tube it is blocked. However, if there is enough water in the drum the water will cause resistance and that’s not the same thing. If it is water you will be able to hear bubbling water when you blow hard.

Remember, if you take off the pressure tubing whilst the washer is full of water you will hear a click, and will feel resistance when blowing down the tube – not because of a blockage in the pressure system – because of the presence of water.


If there is resistance, and it isn’t water, blow harder and see if you can clear the blockage. Sometimes a solid blockage can need a lot of pressure to clear through it. If you blow down and clear something so that you have a free passage of air then you have temporarily cleared it. I’ve known this method clear the fault for a several wash cycles, a few months, or even totally, but most of the time it will only clear it for a while and needs fixing properly asap.

Do not forget to re-fit the tubing to the pressure switch, or the washing machine will overfill and flood, or trigger an abort and error. Also, always watch and test the washing machine for overfilling after interfering with the pressure system. A leak of air from a poor fitting tubing can stop the pressure switch from operating.


Clearing the blockage properly

close up of gunge in pressure chamber

The only way to properly clear a blockage is to remove the pressure chamber bottle and thoroughly clean it under the tap. If you look at the example picture you can see the gunge is caked inside the bottle and there is no way this blockage can be permanently cleared no matter how many times you blow down the tubing.

As the part is usually located deep inside the machine attached to the main tub you will normally need to partially dismantle the machine to get to it. Don’t forget to check the hole leading into the bottle where it attaches to the drum for blockages too.


Finding the pressure chamber

The pressure chamber bottle is at the other end of the small tubing attached to the pressure switch. I’m not able to give specific stripping down instructions. All washing machines are different. Even different washing machines of the same brand can have different methods. With some washing machines the pressure chamber bottle is accessible after taking off the back panel, and with many others you have to take off the front panel.

DIY Repair tips

You shouldn’t be messing with washing machines unless you are experienced at repairing and maintaining things and know what you are doing around electrics. Here is some vital advice – 3 good pre repair tips | DIY Washing machine repair warnings: 8 things you should never do


What causes a blocked pressure system?

Blockages are caused by a build up of grease, bacteria and slime and or limescale. Check out how to prevent this in my article here – Causes of grease, slime and black mould inside washing machines. But if you have a blockage already it is very unlikely you will be able to clear it with maintenance washes or washing machine cleaning products. Believe me I’ve tried.

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7 thoughts on “How to clear a blocked pressure system”

  1. marilyn levesley

    i wish i could find a definite answer as to where the pressure switch is definitely located on a WMXTF942P hotpoint washer, anyone know please advise asap many thank

  2. Marilyn, It’s near the top right near the front of the machine. I’ve got a suspicion mine is faulty becauset the machine doesn’t seem to take in much water any more, leading to less than clean clothes and mould on the rubber door seal.

    To access it, unplug the machine from the mains. Undo the two screws at the back that hold the top cover in place. Lift up the back edge of the cover to remove it. The pressure switch is attached to the right side panel (when viewed from the front) near the top very close to the front. It’s blue on mine and has a 3 terminal small white plug plugged into it. It also has a thin black rubber hose attached underneath leading off to the drum.

    I couldn’t see any continuity on any of the terminals and the switch only seems to softly click when I suck on a tube attached to it instead of when blowing which seems counterintuitive and not what any of the test guides suggest.

  3. I have a samsung echo bubble machine around 4 years old that fills for about 3seconds and stops and has one of these new resistive pressure switches which i thought may be the problem.I have cleared the pressure chamber and ther are no restrictions when you blow down the tube.Being an electrician you could test the old type of pressure switch with a meter when blowing into it. Is it possible you can give me typical resistance readings i should be getting from the device across the 3 pin connector.
    Many thanks
    Phil.

  4. Andy Trigg (Whitegoodshelp)

    Hello Phil. To be honest I can’t see much going wrong with these new type of pressure switches. The old types rarely fail to. They are extremely simple devices. The new type just appear to be a small coil with a magnet. The magnet will be pushed up and down by air pressure in the pressure system. I don’t have full technical specifications but I wouldn’t be surprised if the fluctuations in resistance or voltage within the coil are so small that they are only detectable by the PCB.

    I can’t imagine any problem with the voltages. The only problem I could imagine is that the small coil goes open circuit. Again I would imagine that to be highly unlikely. So if the coil was open circuit there would be no communication with the PCB. That should trigger a specific error code.

    Most washing machines now start up a wash cycle by draining for about 30 seconds. Then they fill with water for about 3 seconds. This initial water is intended to bypass the mains soap dispenser drawer. It is not intended to flush any detergent into the drum. This initial water is intended to run down into the drum and drain into the bottom of the sump hose. A small ball inside the sump hose will be raised up by this water and seal off the sump hose and pump.

    This is intended to prevent detergent being wasted. After this has happened, water will then be directed into the soap dispenser drawer to flush down the detergent. So it sounds to me like this is where the problem potentially lies? If the water that should flush in the detergent is supplied via a separate water valve solenoid than the one that flushes water for several seconds into the sump hose then a fault on this 2nd solenoid may well be the problem.

  5. I have a Hotpoint washing machine and I have the dreaded f05 error, everyone else seems to have the issue where the water isn’t draining. My machine starts a cycle and then comes up with the error, drains ok, any ideas?

  6. Andy Trigg (Whitegoodshelp)

    Hello Steve. The error F05 is covered in a different article Hotpoint Error Code F05 It explains how the error can be caused by not draining or pressure system fault but also other faults, so it may be better to get an engineer.

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