How to clear a blocked pressure system
A blocked pressure system on a washing machine can produce several different symptoms, some of which are easily confused with other faults. This guide explains how to identify whether the pressure system is the cause, how to test it, and how to properly clear a blockage – as opposed to a temporary fix that is likely to recur.
Working inside a washing machine carries real risks. Always disconnect the machine from the mains before removing panels or touching internal components. This guide is intended for those with experience of maintaining or repairing appliances. See: DIY washing machine repair warnings | 3 good pre-repair tips.
Common Symptoms of a Blocked Pressure System
A blocked pressure system can mimic several other faults. All of the following symptoms can also be caused by unrelated problems, so a blocked pressure system should not be assumed without proper diagnosis.
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Machine won’t enter fast spin. After draining the water successfully, there is a click and the machine stops – or it reaches the end of the cycle without having done the fast spin. This is the most common symptom of a blocked pressure system.
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Machine overfills with water.
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Error code during the rinse cycle.
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Machine won’t fill with water and starts washing with an empty drum – which can energise the heater with no water inside, causing damage.
Not entering fast spin, for example, is more commonly caused by an unbalanced load or water that hasn’t drained properly than by a blocked pressure system. See: won’t spin a single item or small load | water isn’t pumping out.
Understanding Why the Pressure System Causes Spin Problems
A blocked pressure system will not prevent the pump from removing water – the water will drain normally. The problem is that the blockage prevents the signal that the water has gone from reaching the control board. The machine therefore believes the water is still present and refuses to enter fast spin.
This is a critical distinction. If the machine is not spinning, the first question is whether the water actually drained. Listen carefully during the drain phase – was the pump running and did the water leave the drum? If there is any doubt about whether the water drained, the problem is more likely with the pump or drain than with the pressure system.
To properly diagnose and understand pressure system faults, read the background guides first: how a washing machine controls water levels | faults on the pressure system.
Testing for a Blocked Pressure System
There is a quick test that can indicate whether a blockage is present. It should only be carried out once the water has fully drained and the machine has cut out without spinning.
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Disconnect the machine from the mains completely before touching any internal components.
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Remove the lid to access the pressure switch and the small rubber pressure tubing that connects it to the pressure chamber.
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Carefully twist and pull the rubber tubing away from the pressure switch. If a click is heard when the tube comes free, the pressure switch is responding to the release of trapped air – this is a good sign that the switch itself is working.
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Gently blow down the tube. If there is resistance and no air passes through, the tube or chamber is blocked.
If there is any water remaining in the drum, blowing down the tube will produce resistance and a clicking sound – but this is caused by water pressure, not a blockage. Blowing harder should produce a bubbling sound if water is causing the resistance. Only carry out this test after confirming the drum is empty.
Temporary Fix: Blowing Through the Tube
If resistance is present and it is not caused by water, blowing harder down the tube may temporarily clear a soft blockage. If air eventually passes through freely, the blockage has been dislodged.
This method can sometimes restore normal function for several wash cycles, several months, or occasionally permanently – but in most cases the blockage will return. It should be treated as a temporary measure while a proper repair is arranged, not as a lasting fix.
Running the machine with the pressure tubing disconnected will cause it to overfill and flood, or trigger an abort and error code. After refitting, run a cycle and watch carefully for any signs of overfilling – a poor seal on the tubing fitting can prevent the pressure switch from operating correctly.
Clearing the Blockage Properly
The only reliable way to clear a blocked pressure system is to remove the pressure chamber bottle and clean it thoroughly under running water. When gunge has built up inside the bottle to the point of blocking it, no amount of blowing through the tubing will clear it permanently – the chamber must physically be removed and cleaned.
The pressure chamber is a small bottle located at the other end of the rubber tubing from the pressure switch, attached to the outer drum. Its exact position varies by machine. On some washing machines it is accessible after removing the back panel; on others the front panel must be removed. There are no universal instructions – each machine is different, and machines of the same brand may have different layouts.
When accessing the chamber, also check the hole in the outer drum where the chamber attaches. This hole can also become blocked and must be clear for the system to work correctly.
The pressure chamber is usually located deep inside the machine, attached to the main drum. Reaching it typically requires at least partial disassembly. If you are not confident in disassembling a washing machine, booking an engineer is the safer option. See: book an appliance repair.
What Causes a Blocked Pressure System?
Blockages are caused by a build-up of grease, bacteria, slime, and limescale inside the pressure tubing and chamber. This accumulation is the same process that causes black mould and bad odours inside washing machines generally.
Once a solid blockage has formed in the pressure chamber, maintenance washes and proprietary washing machine cleaners are very unlikely to clear it. Prevention is far more effective than cure. See: causes of grease, slime and black mould inside washing machines.
Need help diagnosing or repairing your washing machine?
Frequently Asked Questions
What are the symptoms of a blocked pressure system on a washing machine?
The most common symptom is the machine failing to enter fast spin after what sounds like a successful drain. The machine may produce a click and stop, or reach the end of the cycle without spinning. Other symptoms include overfilling, error codes during the rinse cycle, or starting to wash with no water in the drum. All of these symptoms can also be caused by unrelated faults, so a blocked pressure system should be confirmed by testing rather than assumed.
If the pressure system is blocked, will the machine still drain?
Yes. A blockage in the pressure system does not prevent the pump from removing water – the machine will drain normally. The problem is that the pressure system cannot detect that the water has gone, so the machine’s control board believes the drum is still full and refuses to enter fast spin. If the machine is not draining at all, the problem is more likely with the pump or drain system, not the pressure system.
Can I clear a blocked pressure system by blowing down the tube?
Sometimes, temporarily. Blowing hard down the pressure tubing can dislodge a soft blockage and restore normal function for a period. This method has been known to work for several cycles, several months, or occasionally permanently. However, when the chamber itself is caked with gunge, blowing is unlikely to give a lasting fix. The pressure chamber must be removed and cleaned properly to permanently resolve the fault.
Where is the pressure chamber on a washing machine?
The pressure chamber is a small bottle connected to the pressure switch by the rubber pressure tubing, and attached to the outer drum at the other end. Its exact location varies by machine – on some models it is accessible from the back panel, on others from the front. There are no universal instructions as washing machine layouts differ significantly even within the same brand.
What causes pressure system blockages?
Blockages are caused by the same accumulation of grease, bacteria, slime, and limescale that causes washing machine odours and black mould. The pressure tubing and chamber are narrow and trap residue over time. Prevention through regular maintenance washes is far more effective than trying to clear an established blockage. Once solid gunge has formed in the pressure chamber, cleaning products are unlikely to clear it without physically removing and cleaning the chamber.
How a washing machine controls water levels – Faults on the pressure system
9 Comments
Grouped into 4 comment threads.
2 replies 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
1 reply I have Amana Washer Tandem 7300, NFW7300WW01 Often, but not always, it stops while draining on the rinse cycle with Error code F1E1. I did a thorough cleaning of the pressure system, including removing the big rubber boot that connects to the drum. There was a lot of greasy build up so hoped this would fix the problem but it did not. The drain pump was noisy so replaced that with a new one, but did not fix the problem. Looking for any other suggestions.
I have Amana Washer Tandem 7300, NFW7300WW01
Often, but not always, it stops while draining on the rinse cycle with Error code F1E1.
I did a thorough cleaning of the pressure system, including removing the big rubber boot that connects to the drum. There was a lot of greasy build up so hoped this would fix the problem but it did not.
The drain pump was noisy so replaced that with a new one, but did not fix the problem.
Looking for any other suggestions.
Hi Steven. If you post your question on the washing machine forums it can be investigated better than on comments here, which needs to stick to the topic of clearing a blocked pressure system.
1 reply 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?
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?
Likely replying to Steve
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.
1 reply 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.
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.
Likely replying to Phil
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.
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
Likely replying to marilyn levesley
Hello Marilyn. They are described in detail on one of the links in the above article – here with photos Faults on pressure system
Likely replying to marilyn levesley
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.