Whitegoods Help article

Low water pressure and washing machines

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Quick Answer

Modern washing machines use software-controlled fill timers rather than the mechanical timers of older machines. If water pressure is too low to fill the drum within the programmed time limit, the machine aborts the cycle and displays an error code. UK water companies are required to supply mains water at a minimum of 1 bar, which should be sufficient for most machines. Problems are most common with unconventional supplies such as bore holes, wells, or header tanks.

Why Modern Washing Machines Are Less Tolerant of Low Pressure

Older washing machines used mechanical programme timers. During filling, the timer motor paused and waited until the pressure system confirmed the correct water level was reached – however long that took. Low water pressure slowed the fill but the machine still completed its cycle.

Modern machines are controlled by software on a PCB. The fill stage runs on a timed basis – the software monitors the water level and if the required level is not reached within a preset time limit, the programme times out. This triggers an error code and aborts the cycle. A washing machine that worked adequately for years on an older machine may cause repeated errors on a new machine drawing water from the same supply, purely because the new machine’s fill timer is less tolerant.

Why timed filling exists

Time-limited fill stages are a safety feature. If a hose bursts or a major leak develops during filling, the machine will detect that the water level is not rising correctly and stop rather than continue pumping water onto the floor. The timeout also triggers if a water valve fails to open. Manufacturers set these limits conservatively, and in some cases slightly too conservatively for very low-pressure supplies.

Minimum Water Pressure Requirements

Source Minimum pressure Notes
UK mains supply (legal minimum) 1 bar Water companies are obliged to supply at this level. Most supplies exceed this
Electrolux, AEG, Zanussi machines 0.5 bar Maximum fill time of 10 minutes. Below 0.5 bar the inlet valve may not close fully, allowing water to seep in when switched off
Miele washing machines 1 bar Miele engineers can adjust the fill time allowance on some models to accommodate borderline pressure situations
Header tank supply (gravity fed) Minimum 16.5 feet (approx 5 metres) tank height above machine If this height cannot be achieved, a pressure-activated pump is required – not a flow-operated pump
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The inlet valve and very low pressure

Washing machine inlet valves rely on water pressure to close fully. Below approximately 0.5 bar, the valve may not seal completely, allowing a slow seep of water into the drum even when the machine is switched off. This can also be caused by a faulty tap that does not fully close, reducing the effective pressure at the valve. If a machine is slowly filling overnight, check both the water pressure and the condition of the supply tap.

5 Things to Check if Low Pressure Is Causing Problems

  1. Check the supply tap and fill hoses.

    Ensure the tap supplying the machine is fully open. Quarter-turn lever taps can appear fully open but be partially seized internally – particularly the common blue-and-red lever type, which can crack or become caked with debris inside. Check that no fill hose is kinked. If uncertain about flow rate, disconnect the fill hose and run it into a bucket to check the flow directly.

  2. Check the main stopcock.

    If water pressure is low throughout the house, confirm the main stopcock is fully open. If mains pressure is genuinely below 1 bar, contact the water supplier – they are legally required to supply at this minimum level and should investigate.

  3. Replace self-tapping saddle clamp taps.

    Self-tapping taps that pierce a hole in the copper pipe to create a connection often deliver restricted flow because the pierced hole is small and rarely clean. In borderline pressure situations, replacing these with proper isolating valves fitted by a plumber can make a significant difference to flow rate at the machine.

  4. If fed from a header tank, check the tank height.

    A gravity-fed supply from a header tank needs the bottom of the tank to be at least approximately 5 metres (16.5 feet) above the top of the washing machine to achieve sufficient pressure. If this height cannot be achieved, a pressure-activated booster pump is the only solution. Note that a flow-operated pump (as used for showers) is not suitable – it must be a pressure-activated type that maintains system pressure even when no water is flowing.

  5. Try running the machine at a different time of day.

    Mains water pressure can vary depending on overall demand from the local network. In some areas, pressure is noticeably lower during peak periods such as mornings or early evenings. If the problem is borderline, running the machine at an off-peak time may allow it to fill within the time limit.

What Pressure Is “1 Bar”?

1 bar of pressure is equivalent to the force needed to push water to a height of approximately 10 metres. A mains supply at 1 bar can therefore push water up a vertical pipe 10 metres tall and still have water coming out at the top. For most domestic installations this is more than adequate. Properties with very low-lying mains connections or those at the end of long supply runs in rural areas are most likely to experience pressure below the minimum threshold.

Options If the Pressure Cannot Be Increased

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Pressure-activated booster pump

A pressure-activated pump pressurises the household water system to 2 to 5 bar even when no water is flowing. This is the correct type for washing machine use. A flow-operated pump (the type used for shower boosters) is not suitable – it only runs when water is flowing and cannot maintain the inlet valve closure pressure needed by the machine.

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Ask the manufacturer about fill time adjustment

On some models, the fill time limit can be extended by an engineer. Miele explicitly offers this as a service – their engineers can adjust the programme to allow more time for filling on borderline low-pressure supplies. This is likely to be a chargeable service call. It may be worth asking other manufacturers whether similar adjustment is possible on their machines, though most do not offer this.

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Choose a machine with a longer fill timeout

Fill time limits vary between models and manufacturers. Some machines allow more time than others before triggering an error. If purchasing a new machine in a known low-pressure situation, research the fill time tolerance of specific models before buying. Electrolux group machines (AEG, Zanussi, Electrolux) use a 10-minute maximum fill time and work from 0.5 bar – a longer timeout than many competitors.


Frequently Asked Questions

Why does my new washing machine not fill but the old one did?

Older machines used mechanical programme timers that paused during filling until the correct water level was reached, regardless of how long it took. Modern machines use software-controlled fill timers – if the required water level is not reached within a preset time, the programme aborts. The same low water pressure that was tolerated by the old machine’s mechanical system is not tolerated by the new machine’s timed fill stage.

What is the minimum water pressure for a washing machine?

UK water companies are legally required to supply mains water at a minimum of 1 bar. Most machines are designed to work at this level. Electrolux group machines (AEG, Zanussi, Electrolux) will work down to 0.5 bar with a 10-minute fill timeout. Miele machines typically require 1 bar minimum but can be adjusted by their engineers. Below approximately 0.5 bar, inlet valves on most machines cannot close fully, risking slow water ingress when the machine is switched off.

Can a booster pump solve low water pressure for a washing machine?

Yes, if the correct type is used. A pressure-activated booster pump maintains system pressure at 2 to 5 bar even when no water is flowing. This is the type required for washing machine use. A flow-operated pump (as used for shower boosting) is not suitable – it cannot maintain the minimum inlet valve closure pressure the machine needs when idle.

Last reviewed: April 2026. Water pressure specifications are based on information from manufacturers at time of writing and may vary between models. Verify minimum pressure requirements with the manufacturer before purchasing in a known low-pressure situation.

Discussion

102 Comments

Grouped into 102 comment threads.

True but it just goes to show how counter intuitive this low pressure business is. You'd never guess the model would work going by what the manual states and never know these models could actually work in a low pressure setting without asking. So much so that the owner told me he was glad he was unaware otherwise he'd have concluded that a front loader with an overhead tank just 9 feet above would disqualify him from ever owning a front loader. His Bosch model was still on sale as late as last year in India while stock was available. The Bosch model i quoted earlier where the owner had to reset the play button has a 2 digit display. Same drum capacity as the basic model with little more features and one unwanted drawback. 0 replies
Seven

True but it just goes to show how counter intuitive this low pressure business is. You’d never guess the model would work going by what the manual states and never know these models could actually work in a low pressure setting without asking. So much so that the owner told me he was glad he was unaware otherwise he’d have concluded that a front loader with an overhead tank just 9 feet above would disqualify him from ever owning a front loader.

His Bosch model was still on sale as late as last year in India while stock was available. The Bosch model i quoted earlier where the owner had to reset the play button has a 2 digit display. Same drum capacity as the basic model with little more features and one unwanted drawback.

Thanks Seven, It could be they are basic enough to not have time outs and error codes but these days that would be unusual. Appliances can still use error codes if they don't have a physical display by crudely flashing lights or maybe even beeping instead. 0 replies
Whitegoodshelp (Andy Trigg)

Thanks Seven, It could be they are basic enough to not have time outs and error codes but these days that would be unusual. Appliances can still use error codes if they don’t have a physical display by crudely flashing lights or maybe even beeping instead.

Spoke to a couple of people who had the following models Siemens WM07A160ME with the overhead tank 20 feet above. Bosch WAG14060IN with tank just 9 feet above. Manuals for both state minimum 1 bar pressure. The owners have had no problems in operation with either at all. The Bosch was a real surprise, you'd never expect it to work but it does. I asked them to measure flow rates but they were not forthcoming. There is no way either gets anywhere close to 1 bar pressure. The common point with both these two machines is they have no display. So no way for the machine to display any 2 letter error codes. Just because it worked for those models does not mean it will work with others. I notice those two models have been discontinued and even the basic models for either brand these days have displays. 0 replies
Seven

Spoke to a couple of people who had the following models

Siemens WM07A160ME with the overhead tank 20 feet above.

Bosch WAG14060IN with tank just 9 feet above.

Manuals for both state minimum 1 bar pressure. The owners have had no problems in operation with either at all. The Bosch was a real surprise, you’d never expect it to work but it does. I asked them to measure flow rates but they were not forthcoming. There is no way either gets anywhere close to 1 bar pressure.

The common point with both these two machines is they have no display. So no way for the machine to display any 2 letter error codes.

Just because it worked for those models does not mean it will work with others. I notice those two models have been discontinued and even the basic models for either brand these days have displays.

To me they are the same. It's like comparing how much energy someone puts into a run using the scientific measuring system of joules with how far he actually runs. So you might say an athlete uses 1000 joules or the 1000 joules enable him to run 500 metres. If you know an athlete can run 500 metres on 1000 joules you could use the distance as a crude way of describing using 1000 joules. (That's a very crude analogy but hopefully it works :) ) Unless I'm totally misunderstanding something that's what the flow rate is being advised for. The manufacturers know most people can't measure water pressure so they say if water pressure is 1 bar it should fill up x amount of litre jugs? My article quotes a source which says, "1 bar is a pressure that’s capable of supplying water 10 metres high. So if water was fed to a pipe at ground level that was 10 metres tall there should be enough water pressure for the water to come out at the top of it." This is just another variation on the filling 3 litres of water in 15 seconds test for between 0.5 and 0.8 MPa I would expect that the flow rate is defined exactly by the water pressure. :) The old system by the way, when they just waited until the right amount of water went into the machine. Even if it took 10 minutes it would still work. I used to go to washing machines which took an extra 15 minutes to complete a wash cycle but still worked perfectly OK. The only reason they should be worried about very low water pressure though is if it's so low the valve doesn't shut off properly and water seeps in. This did used to happen, but rarely. I can only assume they introduced these time limits of fill to detect water pressure being so low the valve won't shut off. 0 replies
Whitegoodshelp (Andy Trigg)

To me they are the same. It’s like comparing how much energy someone puts into a run using the scientific measuring system of joules with how far he actually runs. So you might say an athlete uses 1000 joules or the 1000 joules enable him to run 500 metres. If you know an athlete can run 500 metres on 1000 joules you could use the distance as a crude way of describing using 1000 joules. (That’s a very crude analogy but hopefully it works :) )

Unless I’m totally misunderstanding something that’s what the flow rate is being advised for. The manufacturers know most people can’t measure water pressure so they say if water pressure is 1 bar it should fill up x amount of litre jugs?

My article quotes a source which says, “1 bar is a pressure that’s capable of supplying water 10 metres high. So if water was fed to a pipe at ground level that was 10 metres tall there should be enough water pressure for the water to come out at the top of it.” This is just another variation on the filling 3 litres of water in 15 seconds test for between 0.5 and 0.8 MPa

I would expect that the flow rate is defined exactly by the water pressure. :)

The old system by the way, when they just waited until the right amount of water went into the machine. Even if it took 10 minutes it would still work. I used to go to washing machines which took an extra 15 minutes to complete a wash cycle but still worked perfectly OK. The only reason they should be worried about very low water pressure though is if it’s so low the valve doesn’t shut off properly and water seeps in. This did used to happen, but rarely. I can only assume they introduced these time limits of fill to detect water pressure being so low the valve won’t shut off.

No, flow rate and pressure are not equivalent in the sense there is no way to derive one from the other. Flow rates are provided i would assume so that there is some easy way to measure whether enough water arrives to satisfy the timer. My tank is at a height of little over 6 metres (20 feet) and i get a flow rate of around 6.5 litres/min. Rough correlation there between height in metres to flow rate. The variance in flow rates stated in the panasonic & gorenje manuals is noticeable, former says 5 latter says 12 L/min with bosch/siemens falling in the middle with 8 L/min. All 3 spec a minimum incoming pressure of 1 bar. So Panasonic's timer is little more forgiving than the germans and so on compared to Gorenje. But you said in the article that incoming water pressure is required to close the inlet valve. I've not understood how, if the timer were reset one time to allow more water to fill that the valve closes eventually at all if the pressure stays low. If the valve does indeed close eventually then its the machine that closes the valve at some point irrespective of the water pressure. Update my mistake gorenje stated 0.5 bar to 8 bar. still the flow rate of 12L/min does not correspond to 0.5 bar in my opinion. The gorenje timer will time out and give errors. 0 replies
Seven

No, flow rate and pressure are not equivalent in the sense there is no way to derive one from the other. Flow rates are provided i would assume so that there is some easy way to measure whether enough water arrives to satisfy the timer.

My tank is at a height of little over 6 metres (20 feet) and i get a flow rate of around 6.5 litres/min. Rough correlation there between height in metres to flow rate.

The variance in flow rates stated in the panasonic & gorenje manuals is noticeable, former says 5 latter says 12 L/min with bosch/siemens falling in the middle with 8 L/min. All 3 spec a minimum incoming pressure of 1 bar.

So Panasonic’s timer is little more forgiving than the germans and so on compared to Gorenje.

But you said in the article that incoming water pressure is required to close the inlet valve. I’ve not understood how, if the timer were reset one time to allow more water to fill that the valve closes eventually at all if the pressure stays low. If the valve does indeed close eventually then its the machine that closes the valve at some point irrespective of the water pressure.

Update

my mistake gorenje stated 0.5 bar to 8 bar. still the flow rate of 12L/min does not correspond to 0.5 bar in my opinion. The gorenje timer will time out and give errors.

I would have thought the flow rate is just a crude method of measuring the water pressure, they are one and the same? 0 replies
Whitegoodshelp (Andy Trigg)

I would have thought the flow rate is just a crude method of measuring the water pressure, they are one and the same?

More low pressure revelations, this time from Panasonic (generic model#s NA-107VC4 & NA-127VB3) "Optimum mains water pressure is 0.1 - 1.0 MPa. If the water pressure exceeds this value, install a pressure reducing valve. Water-flow from the tap should be more than 5 L/min." which corresponds to 1-10 bar pressure. However the 5 litres per minute requirement is odd. A 1 bar minimum pressure means roughly at least 10 litres per minute. Yet the Panasonic manual states it can handle half that amount. So the timer is not going to trip if the water pressure slows down to that rate so long as the flow stays above. But what about the inlet valves. If they're spec'd for 1 bar minimum then a low pressure most of the time may not work out too well. What isn't clear is whether it wants a 1 bar minimum pressure most of the time and can handle pressure as low that amounts to 5 litres/min or Whether it will function at all if the flow rate is little over 5 litres per minute but less than 1 bar. A crucial distinction. It makes me wonder which is the more important parameter to take into consideration. The incoming water pressure or the flow rate ? 0 replies
Seven

More low pressure revelations, this time from Panasonic (generic model#s NA-107VC4 & NA-127VB3)

“Optimum mains water pressure is 0.1 – 1.0 MPa. If the water pressure exceeds this value, install a pressure reducing valve.

Water-flow from the tap should be more than 5 L/min.”

which corresponds to 1-10 bar pressure. However the 5 litres per minute requirement is odd. A 1 bar minimum pressure means roughly at least 10 litres per minute. Yet the Panasonic manual states it can handle half that amount. So the timer is not going to trip if the water pressure slows down to that rate so long as the flow stays above. But what about the inlet valves. If they’re spec’d for 1 bar minimum then a low pressure most of the time may not work out too well.

What isn’t clear is whether it wants a 1 bar minimum pressure most of the time and can handle pressure as low that amounts to 5 litres/min or

Whether it will function at all if the flow rate is little over 5 litres per minute but less than 1 bar. A crucial distinction.

It makes me wonder which is the more important parameter to take into consideration. The incoming water pressure or the flow rate ?

The Gorenje 3 litres of water in 15 seconds test for between 0.5 and 0.8 MPa is useful. 0 replies
Whitegoodshelp (Andy Trigg)

The Gorenje 3 litres of water in 15 seconds test for between 0.5 and 0.8 MPa is useful.

Another possibility is that a lot of the initial water gets soaked up by the dry laundry when it first fills. Also, it's more critical on wash because if there isn't enough water in the heater may not be covered, which would be very bad. 0 replies
Whitegoodshelp (Andy Trigg)

Another possibility is that a lot of the initial water gets soaked up by the dry laundry when it first fills. Also, it’s more critical on wash because if there isn’t enough water in the heater may not be covered, which would be very bad.

Gorenje manual, states the following.. "To ensure correct operation of the appliance, water pressure inlet must be between 0,05 and 0,8 MPa. Minimum water pressure can be established by measuring the quantity of poured out water. 3 litres of water must be poured out from completely opened tap in 15 seconds." Gorenje wants a minimum flow rate of 12 litres per minute compared to 8 litres for bosch/siemens. Even though the minimum incoming water pressure is 0.5 bar, the flow rate or what the machine expects also matters. 0 replies
Seven

Gorenje manual, states the following..

“To ensure correct operation of the appliance, water pressure inlet must be between 0,05 and 0,8 MPa. Minimum water pressure can be established by measuring the quantity of poured out water. 3 litres of water must be poured out from completely opened tap in 15 seconds.”

Gorenje wants a minimum flow rate of 12 litres per minute compared to 8 litres for bosch/siemens.

Even though the minimum incoming water pressure is 0.5 bar, the flow rate or what the machine expects also matters.