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. John:

    The enquiries I made lead to a company who make booster pumps and they suggested “if noise is not a problem I would put these two products together..”

    Unfortunately the two products cost nearly £200, would probably need fitting by a plumber and looked bulky and by their own admission noisy. I decided it wasn’t an ideal solution at all.

    If you are getting 0.95 of a bar I will contact Miele and ask their technical guy if it’s possible to adjust the time somehow to make it work. It’s a long shot but I will let you know what he says.

  2. John:

    I’ve refreshed the main article adding more information although nothing approaching a cure-all I’m afraid. I’ve been in touch with the Miele technical guy and still trying to clarify whether they are able to adjust anything I’m afraid. I will post further info asap.

    Miele told me that their machines should work with as little as about 0.6 bar.

  3. Thanks to your latest advice and the plumber’s measurements of pressure in my system, I have now made more phone calls and made some progress. Whereas first time, Miele Customer Service told me there was nothing I could do, I have now been told they will come out and adjust the settings to take a lower pressure – for free!

    I cannot believe we have had so much hassle when they could have suggested this earlier. Thanks again for your help.

  4. Thanks for the update John. I spoke to the guy in charge of the technical side at Miele and he said they would have a look for you but I didn’t receive a reply when I followed it up by email.

    Please keep us informed. I hope it can be resolved asap.

  5. Yes Andy, it’s sorted. A Miele engineer finally came and in 1 minute adjusted the time it takes to fill, and it works fine. He couldn’t understand why there was nothing in the manual about it, because he says it is possible to do it yourself manually! I think he is absolutely right, and it should be included in the spec for the machine etc as well, and retailers should know how to deal with the problem. I was thinking of writing a complaint to Miele, but some one suggested it might be better to ask Which? to do it – as you know the problem must be quite common. Anyway, thanks for all your help on this.

  6. Great news John. It’s unfortunate that it took so long. I don’t know how you managed.

    If the adjustment could be made available it would be much better. However, unless the code or special button combination to get into the configuration only affects the time taken to fill they wouldn’t want people to have access to it.

  7. I have a Bosch Exxcel WAE24467GB washer. I live in a top floor flat with storage tank fed cold water supply. The machine works ok but has posted a few low pressure error codes (4-5 times) but on the whole works ok. I’m guessing my water pressure is borderline. Will I make things drastically worse, do you think, if I use the cold water supply to feed a coffee machine that needs plumbed in. I propose to split the supply with a T-joint and use 3/8″ tubing to connect the two appliances. The length of connections is very short. I just bought a water pressure gauge but I see that you have to measure flow to accurate predict whether the flow will be enough for the machine. I don’t want to purchase an expensive coffee machine, plumb it in, and find that the washing machine is affected! Any advice would be much appreciated!

    Steve

  8. Hello Steve: I can’t claim to be an expert on plumbing but this is how I see it –

    I don’t think splitting the supply would affect the water pressure to the washing machine as the supply to the washer would presumably be the same as it is now. If you just split the supply to run off a short distance to another appliance then only when that appliance is taking water should the pressure to the washing machine be affected.

    When the other appliance isn’t drawing water, then the water would just run up to the appliance and reach a dead end. I would expect as it’s not drawing any water it couldn’t be diverting any water pressure from the washing machine.

    That’s how my logic sees it. I hope it’s right.

  9. Very interesting! I’m about to order a Bosch WAE24467 washer
    but I’m worried about our low water pressure which is caused by furring up of the metal supply pipe running from the road under
    the garden and the house to the rear of the property. It can only
    worsen over time but is apparently my responsibility. Our existing
    Bosch washer has refused to take powder and conditioner from
    the tray for quite a while now but using wash tablets in a bag in the drum has overcome that problem. Items needing fabric conditioner have to be rinsed in the sink and spun again—very
    time-consuming.So the question is; can the water co. be pressured
    (forgive the pun) into putting this right?

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