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?
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.
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
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.
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.
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.
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)
It’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 (below), 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.
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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Hi Faith,
I had your exact problem of the washing machine filling up and flooding the kitchen when not in use.
The cause was my water softener seal breaking down and putting tiny plastic beads into the water which jammed the valve open at little bit in the washing machine, and caused the machine to eventually flood.
To test, get a very clean large bowl, quater fill it with water, and very gently swill the bowl round to create a circular vortex in the bowl. This action will cause the beads to come to the middle of the bowl and you can see them as tiny black dots.
Do a sanity check, and bypass the softener and you should see that the beads are not there when the water does not come through the water softener.
I hope this has helped.
Hello again :)
Thank you both Washerhelp and Neil for your comments, they’re much appreciated.
Finally, after several months, I think the “problem” is solved and want to share my joy with you, hehe!
First, I tested the tap like you suggested, Washerhelp, closed the tap and disconnected the hose to see what was up. We don’t have the blue tap, but this green knob that turns in a circle to open and shut – and sure enough, while it wasn’t pouring there was a steady drip coming from the tap even when it was shut off.
The solution presented itself quite by accident – I was running around busy one day, and completely forgot to shut off the valve when the machine completed the cycle and the clothes were out! Lo and behold, NO water seeped into the machine. This only occurred to me several days after the fact, and I belatedly decided to shut off the tap just to be on the “safe” side. What happened? There was water in the machine the next morning. I drained it, but it just kept coming back. So I opened the tap fully, to test, and just left it like that – it’s been almost a month, and there has not been one instance of water filling the machine overnight!
It seems to me (and this is only a guess of course), that my previous washer had the problem with our low water pressure when the tap was left open – because the pressure was too low the valve didn’t close properly, and water would seep into the machine. As a result, I got into the habit of shutting off the tap. When that washer went crazy with a bunch of (non-related) problems we replaced it. This new washer seems to be fine with the fact that our water pressure is relatively low – as the valve actually doesn’t have a problem shutting off when the tap is actually left open, and the cycles complete around the “scheduled” time.
Thus, I conclude, the problem with this new washer arose not from low water pressure, but from my previously developed habit of shutting off the tap (that never actually fully turned off). The steady drip of water from the faulty tap was definitively not enough to shut off the valve and kept seeping into the washer.
I am ecstatic about this discovery, and I sincerely thank Washerhelp once again, for both the answer and the wealth of information provided on this site, which helped me rule out numerous possibilities that only baffled an amateur like myself – as well as helped me learn quite a bit about my favourite home appliance. :)
just want to explain my situation: I use a simple water pump to pump it from a private well from 20m depth up to the water tanks situated 2-3 meters above the ground in the attic. Right now, the water pressure is not so high from the water tanks.
I purchased a new LG washer with requirement 0.3 bar but I still want to boost the pressure of cold water supply from the tank (not from the well).
What is the eficcient low cost water pressure booster pump to do this ? (I need only 1 bar pressure which I assume is sufficient for showering, dishwashing, etc)
registoni: I don’t have any experience with these pumps at all I’m afraid.
One pump experience story for you:
we specced a fancy mixer tap on the sink in our new kitchen. But as it turns out, the inlet pipes to these things are really thin! Flow from our mains pressure cold is fine; but the hot was a lousy trickle due to low pressure from the low header tank in our flat. Probably we should have replaced the sink with something with two separate taps with decent size inlets (which is what everyone else in the block with the same problem has, we realised later), but instead we just put one of these pumps into the hot pipe under the sink:
(just one side of it used, despite the instructions warning you both sides should be plumbed. It was cheaper than any similar single-pump device though). Now we have gushing hot water at the cost of some under-sink noise while it’s running. We’re on the second one in ~9 years. Not sure if we were just unlucky with the first one, or we’re basically abusing it and it broke prematurely.
We did briefly consider also trying such a pump as a solution to the washing machine fill-timeout problem (which takes its cold from a header tank, not mains unfortunately) and which originally led me to discover this forum, but something put us off (maybe something above on this page even?) and made us think this wouldn’t work well (some bad interaction with the intake valve on the gadget or something like that). Seems to be fine for boosting tap pressure though, and the thing is obviously designed for showers.
Tim
Sorry, no idea, I’m not a plumber… I do know a cottage which gets water from an adjacent stream with little pressure and has a pump with a compression chamber with a rubber diaphragm in it which keeps the water pressure up after the pump has stopped running (a bigger version of your linked pump, I think)… supposedly it’s more like having “proper” water pressure and is supposed to generally work better than simply having an on-demand pump in the circuit. There’s no modern washing machine there (just an ancient twin-tub!) so I can’t comment on whether it’d help you though :^)
BTW thanks Faith, I’ve added a link to your comment at the bottom of my article.
Thanks so much for this article and this incredibly useful comment thread. This is almost the only resource on the internet, that I could find, that talks about this issue. I am just adding my 2c of research to the general body of information, out of gratitude to everyone else above.
I have an internal storage tank in a loft that gives me a flow rate of approx 5-6 liters per min. As per Tim’s comment above (1 bar ~ 8 lpm )then mine would work out to a pressure head of about 0.625 bar. (I think, this is assuming a flow through a standard 1in tap??) I am not sure how pressure head correlates to flow out of a tap of specified diameter. Please correct me if I am wrong.
It seems to me there are 2 independent factors to consider:
1. flow rate: to ensure that the machine fills up in a specified (pre-programmed) amount of time.
2. pressure head: to ensure that the inlet solenoid valve can be turned off and on.
Now most manufactures (in fact almost all) specify only factor #2 in their manual. Whereas it seems to me that factor one is almost as important as well. I could throttle a small flow rate using a narrow tap and generate enough pressure to satisfy #2 but that will still not get the machine to work as planned.
A siemens rep told me their machines need a flow rate of 8-10 lpm to work. Some LG machines I found could work on a pressure head of 0.3 bar, but no one had any idea about the flow rate needed.
This data would probably be available with the machine DESIGNER, but in this globalised era, finding that one person halfway around the globe seems impossible. With a lot of these firms, there is no way to get reliable technical information out of the system.
I did not find any machine that could reliably work with my restrictive parameters (0.6 bar, 6lpm) as per the incomplete data that I got from the manufactureres (LG, smasung, whirlpool, siemens, Bosch) so I finally went for a very old school and bought a twin tub semi automatic machine, which works just fine.
Of course it means some more labor, but I definitely did not want to go thru the hell of a booster pump, (more things to potentially fail), and I did not want to risk spending money on a machine that may not have worked.
SO this is the tradeoff that I made. Apart from the grunt work involved in the semi-auto,. I am very pleased with its wash, it takes less time and water too.
thanks and regards.
I think there are many model of washers that can do work at water pressure less than 0.5 bar. Mine one is LG direct driver inverter plus model, claims to be working at only 0.3 bar. I connected it to the pipes coming from under the water tank (2 m from above the ground) and it did worked fine.
Just to be on the safe side, before washing I refill to the top the water tank so that natural water pressure would be the highest available.
It might be time for them to redesign the water valve. It’s always seemed bizarre to me that a water valve needs a certain amount of water pressure to stay closed. Why can’t a water valve solenoid properly shut off on its own without needing assistance from water pressure, which clearly isn’t reliable enough?