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 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.
Several Which? Trial Offers available to allow you to research all future purchases and see expert reviews and recommendations. Easily save a lot more money than it costs. I know I do.
H.Davies says
This has been a really useful article as we have just been told that
problems with our new John Lewis washing machine are down to low water pressure. Our water is drawn by pump from a well. What is the best method of increasing the pressure?
Washerhelp says
There are pumps designed to pump water from basements to supply a washing machine by companies like saniflow. They can bring water pressure up to the required level. You’d need to research if this is appropriate for your circumstances and how you would connect one.
Joe Frannino says
Your article expalined the mystery as to why my 4 month old GE washer keeps overflowing. Twice the water that oveflowed was minimal and easily cleaned up with a towel. The third time it flooded 3 rooms. GE tech came out and found nothing. I mentioned your article as to the problem coming from low water pressure suplied by the water well. He said it was not possible. Have you done any additional research on this problem and is there anything I can do other than stand next to the washer while washing? I was not at home the last time it overflowed but from the amount of water (oveerflowed over the outside porch) I doubt a pan under the machine would have been able to contain the water. Do they still make washing machines using the old method of checking the water level? May be cheaper to buy a new washing machine with the old technology than having to replace hardwood floors and sub floors.
Washerhelp says
Hello Joe: As far as I know all washing machines in the UK now use software built into a control pcb to run programmes as opposed to the mechanical clockwork- timers of the past.
The only way your low water pressure could be associated with a leak is if it is too low to shut off the water valve properly. This could allow water to slowly seep into the soap dispenser where water goes into the machine. It’s less likely to cause problems whilst the washer is running apart from the aborting problem due to timing out on fill.
If a washer connected to very low water pressure isn’t shutting off the valve properly then a washer could start to fill up with water inside the drum overnight and eventually run out of the dispenser drawer or other places.
Anyone concerned about this should turn off the taps each time they finish washing. However, I would speculate that if anyone’s water pressure was so low as to allow this, then the modern washing machine should probably not work properly as described in this blog article. This is precisely why manufacturers introduced time limits for fill. Turning off taps when the washing machine is not in use is definitely wise, and advised by all manufacturers.
In other words, manufactures are deciding that if your washing machine doesn’t supply a certain amount of water in a set time they don’t think your water pressure is high enough and may have problems closing the valve off properly, so they refuse to work.
If low water pressure is the cause of your flooding you should be able to see a slow dripping of water in the soap dispenser with the drawer taken out and you should be able to see that water is filling up inside the drum when not in use. (NOTE: another cause for water running into the washing machine when not on use is siphoning from an incorrectly fitted drain hose connected to the u-bend – Washing machine fills with water overnight or when not in use)
The problems raised with the blog article are that it’s often a bit of an arbitrary decision because the time allowed is clearly set too low with some washing machines. This accusation is valid because some people have used a washing machine without any problems for many years, but when they replace it with a software controlled one it keeps aborting on fill and will not work. However, a washing machine obviously will work OK because their old one did.
H.Davies says
To follow up my experience with the John Lewis washing machine – two engineers’ visits resulted in the conclusion that the water flow was too low. However each time the error message was something like ‘Check hose and connector’. I realized that neither engineer had really done anything about this this as they were so convinced it was low pressure. So as a last-ditch attempt to sort the problem, I removed the hose which incidentally has a fail-safe valve built-in, reversed it and flushed it through via the tap. Nothing came out but – -touch wood on reattaching the hose correctly the problem seems to have disappeared for the time being!
John Moore says
We have low water pressure. The system is gravity fed from a holding tank fed by water pumped up from a spring. By the time it gets to the kitchen taps water pressure in the hot and cold taps is about the same, the hot tank outlet being maybe 2.5m above the taps. There is a header tank about 1m above the hot water tank. The washing machine inlet is about another 1m lower than the kitchen taps. Is this sort of pressure likely to be sufficient to run a modern washing machine, as our old one an Indesit 1063W has about had it?
Presumably I could measure the water pressure at the washing machine inlet by attaching a hose and seeing to what height the water rises? I seem to remember 1 bar being 10m head of water?
Washerhelp says
Hello John:
I’ve added an update to the bottom of the original article (scroll back up to it), which you may find helpful. I would go for an Electrolux washing machine to be on the safe side as they say they only need half a bar water pressure. That I presume means 5 feet of pressure instead of 10.
If still having problems you would need to try doing something about it as mentioned in the quote from the Electrolux spokesman. Electrolux are one of the best makes in the mid price range.
John Willis says
A really useful article, thank you, but can you suggest a way out in my situation? I have bought a new Miele machine – expensive but with a free 5 year guarantee! – and did not discover it requires 1 bar of water pressure until getting to the technical spec at the back of the manual (buried deep inside the packaging). I only have about 6m of fall from my cold water tank to the machine, which aborts every time I try to wash with it, with the Check Inlet light flashing all the time. To connect the mains to the machine will be an expensive process as it is an old rambling house where lots of bits and pieces have been added on by everyone who has lived there. And I could have bought a Zanussi and saved myself the trouble.
Miele say they have no responsibility as there is no fault with the machine; they won’t take it back because I have started to use it; and the retailer disclaim any responsibility too. Surely suppliers should make this kind of thing clear before you buy?
Have you any suggestions on getting round this, or comments on what my rights are?
Washerhelp says
John:
This is a very awkward problem because it’s hard to find someone to blame. In reality most homes have much more than 1 bar of water pressure. The problem seems to occur mostly when someone (like yourself) has connected their washing machine up to a non-conventional water supply such as a bore hole, well, or a gravity fed storage tank.
Most washing machine manufacturers design their machines to work on at least 1 bar. As I mentioned in my main article Electrolux (who also make AEG and Zanussi) are particularly generous with the time allowed for fill, and their technical spokesman says they will work on just half a bar.
Miele (amongst other manufactures) have made a decision to play it safer and insist on at least 1 bar. Their machines should work with any mains plumbing*, which is available in the overwhelming majority of cases. They say that less than that could adversely affect the water valve’s ability to shut off properly. However, I expect there is a margin built in. Let’s say a washing machine has just 1 bar of pressure but whilst the washer is filling there is a drop in pressure due to peak demand or someone drawing off water elsewhere. The pressure could drop below the required amount.
You could argue that’s what the program software is supposed to protect against though, and it should be sufficient to produce an error in such an instance and abort the programme. The counter argument to this is that if starting off with only half a bar, if pressure dropped enough to stop the valve shutting off then aborting would be futile. This is because the valve would simply not be able to shut off unless enough water pressure returned. (Water valves in washing machines need the pressure of the water to shut off properly. It sounds bizarre but it’s always been so)
Who’s to blame?
The dilemma is in deciding who’s fault it is that your new washing machine won’t work and therefore who should bear the cost of it being replaced. It’s hard to blame Miele as they are designing to work on mains water pressure in a safe manner as they always have done. It’s hard to blame the retailer because they didn’t know you would be connecting it up to such low water pressure. Sales staff would be as unaware of this issue as the public and it may only be one in many thousands of customers that aren’t connecting the washer to the mains water supply. That only leaves you, and you aren’t to blame either. How could you possibly know the Miele wouldn’t work? Especially if your previous washing machine did work.
If I was forced to blame someone, I wouldn’t be able to although it’s the seller you have the argument with in UK consumer law. You could always ask what Citizens advice think.
The most desirable option would be if possible to keep the Miele and connect up a booster pump. This would solve the problem for all future washing machines too. I’ve made enquiries about if such a booster pump is available and will let you know if they are fruitful.
*All water authorities are legally obliged to supply water at a minimum of 1 bar in the UK. Therefore any washing machine sold in the UK needs to work on a minimum of 1 bar. If a washing machine connected to the mains water supply does not work because of low water pressure and you know you have the stop tap adjusted correctly then the local water authority should be obliged to ensure you are supplied at a minimum of 1 bar of pressure.)
John Willis says
Thank you ever so much for this – I have only just realised you replied.
I have talked to CAB & Trading Standards and all agree with you that no one can be blamed. I am still trying to come up with ideas as all the plumber can suggest costs many hundreds of pounds in his labour. He has meanwhile fitted a flexible hose from our outside mains tap. If you can find a suitable booster pump that would be great. He has measured the pressure as 0.95 of a bar but that still isn’t enough for the machine.