Low water pressure and washing machines

Low-water-pressure Low water pressure has become a big problem for a minority of washing machine owners due to the way modern washing machines work. Some people find that even though their old washing machine may have been slowed down by a lack of good water pressure, it was still able to complete a wash cycle.

Yet when they buy a new one it sometimes refuses to work.

Why is water pressure so critical now?

Stop-watch In the past, washing machines were controlled by simple mechanical program timers. When filling with water the timer motor in the programmer was turned off. The whole program came to a stop until the pressure system detected the right level of water had been reached.


It then powered up the timer motor, and the washing machine commenced washing or rinsing. This system was highly tolerant of low water pressure. It wasn’t dependent on time. It was just dependent on getting the correct amount of water inside eventually.

Washing machines are now far more sophisticated and most are controlled by software built into PCBs. The wash cycle is controlled like a computer program. This is an excellent advancement and brings lots of safety features and efficiency improvements.

One side-effect is that without a high enough water pressure many washing machines will detect a fault and abort the program – even if the same water pressure has sufficed for many years with the old washing machine.


Time-out The amount of time allowed to fill can vary from machine to machine. So some washing machines are more tolerant than others (more on this later). Some washing machines may allow too little time to fill and can abort the program unnecessarily at times.

The fact that the previous washing machine worked perfectly OK with the old mechanical timers backs this up.

How does low water pressure affect a washing machine?

When reaching a fill section, the programmer now no longer shuts off. Instead, the clock is ticking.

The software constantly checks to see if the correct water level has been reached. If the correct water level has not been reached before a pre determined time limit then the program times out. This usually triggers an error code, and aborts the wash cycle. When setting the time limit though, some manufacturers may set it slightly too cautiously.


Why do they do this?

Setting a predetermined time limit for specific events is a good method of averting potential disasters. It can prevent things like flooding or overheating. Suppose there’s a big hole in something and the washing machine is trying to fill the drum – but the water is just pouring onto the floor.

If unattended this could be a disaster. So if the washing machine times out after 3 or 4 minutes because the water level hasn’t risen inside the drum, this is very desirable.

Also, if water pressure falls below a certain level there is another safety issue because the washing machine fill valves need a minimum water pressure in order to close off properly. This can cause water to seep slowly into the drum and is arguably a very silly design.

What can you do if you have low water pressure?

There may not be an easy answer. Especially if you don’t have access to a mains water supply and rely on a bore hole or a well to supply water. In these cases you would need to do some research into using an appropriate booster pump.


It must be a pressure activated type i.e. pressurises the house water system to approximately 2 – 5 Bar (depending on pump used) even when off. You cannot use the flow operated type (as used for shower pumps).

Miele washing machines

If your washing machine is a Miele, it may be possible for one of their engineers to adjust the time limit on your machine to allow a little longer to fill.

I don’t know any other manufacturers that can do this, and I especially doubt most ordinary ones do but you could always try asking. If nothing can be done and you can’t fix the problem you may need to replace the washer with one more tolerant to low water pressure.


Miele’s technical manager has told me that their machines will work down to almost half a bar. So anyone affected must have a very low water supply. Also, Miele washing machines can be adjusted by a Miele engineer to adapt more to low water pressure situations. I’m not sure exactly what they do but I suspect they can increase the amount of time allowed for filling.

It’s a sign of the extra sophistication you get with Miele product but of course this is likely to be a chargeable service as it’s not addressing a fault on the machine. It should rescue you if you just laid out for a new Miele, which didn’t work due to low water pressure and the water pressure was only just too low.

The vast majority of people have perfectly adequate water pressure. This article is for those who are aware that they have very low water pressure, or for those where their water supply may be from an unconventional source such as a bore hole or well. In such cases some sort of pump booster would be needed if pressure was too low to run a modern washing machine.


What is 1 bar of water pressure?

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.

Water companies in the UK are obliged to supply mains water at a minimum pressure of 1 Bar. Washing machines should be designed to work on a minimum of 1 bar so unless you have an unconventional supply you shouldn’t (in theory) be affected. I’ve been told by an Electrolux that their washing machines will work with a minimum of .5 a bar. Miele washing machines need at least 1 bar.

If concerned about very low water pressure, ask your local water authority what the water pressure is to your home. If they say it is 1 bar or over then modern washing machines should work. If not you would need to complain to the water authority that your supply isn’t good enough to use a washing machine with.

Of course you need to make sure nothing within the house is restricting the water flow like the stop tap being turned down low.


5 things to try if you have low water pressure

1 Make sure the tap supplying the washer is turned on fully. Also make sure that no fill hoses are kinked. Ensure the tap isn’t faulty. The ubiquitous taps with the blue and red levers in particular can often partially seize up inside. They can become caked in sludge inside, or the plastic operating lever can crack meaning that the tap appears to be fully on but it isn’t.

2 If it’s just general low water pressure all over the house and you have already got the main stop cock on full, get in touch with your water company who may be able to help. Water companies in the UK are obliged to supply mains water at a minimum pressure of 1 Bar. This should be high enough for a washing machine. If you don’t think your water pressure is particularly low, test by disconnecting the fill hose(s) and running the water into a bucket to check the flow rate in case the low pressure is just at the washing machine’s tap.

3 Don’t use those self-tapping self-plumbing taps that just clamp on to the copper pipe and pierce a hole to “tap” into the plumbing. Most of them pierce such a small hole (and often not cleanly either) that you probably won’t get a full water flow. In border-line cases it may be enough to prevent the washing machine getting the right amount of water in time. If you have those taps fitted and especially if you didn’t have trouble in the past then getting them replaced with proper taps may make a big difference.


4 If the washing machine is supplied with water by a header tank instead of mains water then it needs to be high enough to create an adequate water flow. However, raising it may not make enough difference unless you can raise it high enough and that’s not always possible. Here’s what Electrolux’s technical spokesman told me –

.. in order to obtain the minimum pressure, there should be a minimum vertical distance of 16.5 feet from the bottom of the tank to the top of washing machine. If this is not possible i.e. a bungalow or flat, then the only other option would be to fit a pump. However, this must be a pressure activated type i.e. pressurises the house water system to approximately 2 -5 Bar (depending on pump used) even when off. You can’ use the flow operated type (as used for shower pumps)

5It’s possible that your water pressure may vary, and be slightly stronger or weaker at certain times of day, especially if you live in flats. At weekends or after work for example it could be that more people are drawing on the water. So try changing when you put the washing machine on. It’s a long shot, but if borderline it could make a difference.

UPDATE: I’ve managed to get a comment from a technical person at Electrolux who make Electrolux, AEG, Zanussi and Tricity washing machines which may be of use to anyone with known low water pressure such as water supplied from wells or tanks. Here’s what they said ..


All of our washing machines are now electronic and incorporate a maximum time fill of 10 minutes, the minimum water pressure required is 0.5 Bar (Maximum 8 Bar), this minimum pressure is required to ensure that the valve closes completely, (if less than 0.5 Bar there is a possibility of water entering the machine even when off electrically).

In low water pressure areas, we recommend that the machine is tank fed, but in order to obtain the minimum pressure, there should be a minimum vertical distance of 16.5 feet from the bottom of the tank to the top of washing machine. If this is not possible i.e. a bungalow or flat, then the only other option would be to fit a pump. But this must be a pressure activated type i.e. pressurises the house water system to approximately 2 -5 Bar (depending on pump used) even when off. You cannot use the flow operated type (as used for shower pumps)


Anyone looking for a pump to increase their mains water pressure should Search Google for – pump increase water pressure

Further update:

A comment from Tim has highlighted a Panasonic washing machine, which he says works as low as 0.3 bars and has got it working in his low water pressure situation.

Update:

A design anomaly or flaw with washing machine water valves is that very low water pressure can cause the washing machine water valve to not shut off properly allowing water to seep into it overnight. This shows the reason why manufacturers say you need a certain minimum water pressure although in this particular case it was caused by a faulty tap that didn’t actually shut all of the water off reducing the water pressure down so low the valve couldn’t shut of.

It does seem a very flawed method of stopping water from entering a washing machine, that is, using the pressure of the water itself to shut off the valve – when if the pressure falls below a certain level it fails to shut it off.

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103 thoughts on “Low water pressure and washing machines”

  1. Barry: I understand they are obliged to supply a minimum of 1 bar pressure to your house. It depends where their delivery point officially starts though logically it should be at your main kitchen tap.

    However, there is a difference between water pressure and water flow so they may well be supplying sufficient pressure but if the water flow is reduced by furring of pipes that’s possibly another matter.

  2. Thanks Andy. I’m pretty sure the water co’s responsibility ends at
    the property boundary; hence the scary junk mail from utility co’s
    offering insurance against leaks in supply pipes underground
    though a trawl of the small print reveals my furry pipes aren’t
    covered.

    I’m going to try an old Indesit machine I have which is ok down to
    0.5 bar, according to the instruction booklet. I’ll let you know in a
    week or so.

  3. Please do Barry: I wonder why the pipes are only furring up from your boundary onwards? Have they said what they blame for the furring?

    Unless the bore of the pipes to your boundary is much bigger than the ones taking the water into your house it doesn’t make sense why only your pipes are furring.

  4. The supply pipes from the mains in the road are metal and only
    about 1″ diam. The furring is part corrosion, part deposits. Sounds
    like a recipe for disaster if the corrosion causes a leak.

    The new spare machine works fine but, like the old one, doesn’t take up the fabric conditioner. I think my only remedy is to ask
    the water co. to install a new supply to the back of the house
    where my existing stop-cock is.(The back wall is on the boundary
    of the property) This would entail the new supply going about 15mtrs under a footpath.

  5. Hi i bought a bosch28363, a couple of days ago, ahd it all connected up, but wont work it keeps giving me the error code for low water pressure. My old hoover machine worked marvellously for a few years. I am connected to the mains supply. What can i do..

  6. Lindsey: You need to make sure the water supply is still there by checking the tap is on full and that the hose hasn’t got kinked.

    It’s also possible that even if the tap looks on, if it’s the type with a plastic lever they are known for sometimes going faulty so they appear to turn on but don’t fully. Sometimes this is caused by the plastic lever cracking so it rides over the metal valve it’s supposed to be turning.

    The best way to check is to turn the tap off, disconnect the hose from the washing machine and then hold it over the sink or into a bucket whilst turning the tap back on. Check that there is full water pressure.

    If you can’t see anything wrong but the water pressure is low then you may just not have enough pressure to run most modern washing machines as described in my article. If your cold water supply is from an unconventional source such as a well or a tank something needs doing to sort it.

    If your washer is connected to the mains water supply and stop tap is on full and you have a low water pressure you may need to ask your water company to check you are getting the required minimum water pressure or call in a plumber to have it checked.

    Find your local water authority (please report if this link no longer goes to the right page as they keep moving it. Use the “contact” link at the top of this page – Many thanks)

  7. Very useful – in fact the article confirmed the resolution of the ‘problem’ we had with an AEG we bought second hand recently. It was in mint condition and had had one year of light use, but it kept hanging at the rinse fill stage showing a C1 fault. We were running it, as we had our previous machine, a WhirlpooI, from the cold tank in the loft. I’d checked the inlet filter was clear, removed the mains pressure restrictor, replaced the 3-way inlet valve, the analogic sensor and the 2-level water sensor, all to no avail. In desperation I got an chappie from Swift Appliance Services to call who confirmed that I’d done everything – except check the water pressure. It was only then – having spent £100 on parts and a visit – that I found the article above. I rigged up a temporary mains feed and…bingo! …no C1 fault and no hanging.

    Hindsight is such a gift, no?

    KevinF.

  8. Thanks Kevin: It’s very easily done something like that. When diagnosing a fault it’s common to assume the cause is more complex than it really is. Many people trying to sort out a dead appliance for example fail to check the wall socket, which should be the very first thing to check.

    Your example was similar, although if your previous washing machine worked OK it’s not surprising you didn’t suspect the water pressure. That’s why I wrote the article because no one would suspect the water pressure if it hadn’t changed and their previous washing machine worked OK.

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