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Blog > White Goods articles > Washing Machines & Washer Dryers > Don’t connect the hot water supply to the cold valve on a cold-fill washing machine

Don’t connect the hot water supply to the cold valve on a cold-fill washing machine

I’ve had several people ask whether it’s possible to connect a cold fill washing machine up to the hot water supply. They were unhappy about the disappearance of the hot water valve in UK washing machines.

Many people who are using solar powered energy to heat their water, or who had another cheap or environmentally friendly supply felt that the advantages of their environmentally friendly and economical hot water will be wasted by not utilising their hot water supply.

The answer to the question is no, for the following reasons -

A full explanation as to why almost every washing machine is cold fill these days is here – Should I buy a cold fill washing machine or hot and cold fill?

Written By - Washerhelp on May 24th, 2007 with 32 comments
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#1. June 28th, 2007, at 11:47 AM.

I want a washing machine with a hot water valve – Whitegoodshelp Blog: Can you connect an environmentally friendly and economic hot supply to the cold valve to utilise it? The short ...

Wookey Wookey
#2. February 22nd, 2008, at 1:50 AM.


The problem of the incoming water being too hot is easily dealt with by fitting a thermostatic mixing valve set to 30C (or 40C if you use that wash temp).These are now widely and cheaply available.

Washerhelp Washerhelp
#3. February 22nd, 2008, at 12:18 PM.


Hello Wookey. Thanks for your comment. I’m not sure which angle you are coming from though. The scenario in the article is of cold fill only washing machines with only one valve. If the hot water was connected to it instead of cold the problems I listed would be experienced. If you mixed a hot and cold supply to a thermostatic valve then the water supplied would always be at that temperature.

This would mean all rinsing would be done at 30 or 40 degrees which would reduce rinsing efficiency. It would also waste a lot of heated water because only a small amount of warm water is needed for wash and all rinsing needs cold.

If you mean the manufacturers should fit a thermostatic mixing valve and make washing machines hot and cold fill again the problem is that it takes so long for hot water to start running through to the machine that it’s already finished filling up by the time it does. In order to use hot water you’d have to let the hot valve run until it was delivering hot water and monitor the temperature. Then either store the cooler water that cam out first (but there’s no space to store it) or pump it down the drain and waste it. Even then, the simple act of drawing off water from the hot supply means that extra hot water would be drawn into the plumbing pipework which is likely to just cool down and be wasted. Cold water would top up the water in the cistern and cool down the rest of the hot water in the tank which may then need heating up further.

I have to say I can see why manufacturers decided it’s simpler and more economical overall to just take in cold and heat it up. The fact that a small minority of users may have ideal set ups with short pipe runs, solar powered heated water and maybe insulated pipes doesn’t detract from the fact that overall, chances are that the UK will use much less energy using cold fill washing machines than hot and cold. I remain open minded but am mostly convinced of the argument.

lemurtail lemurtail
#4. July 24th, 2008, at 1:40 AM.


Would it damage my washing machine if I attach a hose to the hot tap and channel it into the drawer when the cold water is going in?

If I do this will it save time as the water won’t have to be heated up, or will the machine automatically heat the water up anyway and cause the machine to overheat?

OK, you can tell from those 2 questions that I haven’t a clue how washing machines work but I’d like to know the answers as I know several people who are wondering the same things. I’d rather not risk finding out by trial and error that I ‘ve written off a new washing machine!

For the record, from the late 80’s early 90s, I used to obtain endless hot water from an experimental solar panel (now defunct) so it always made sense to use a hot and cold fill machine. Running costs were very cheap, and my washing was never damaged or overheated. Even though I mainly used 30 and 40 degree washes, the hot water definitely flowed into the machine. It filled up in a fraction of the time as my new machine does.

I don’t see the point in saving up for a domestic solar panel to heat water if that water can’t be used in washing machines and presumably dishwashers too?? Cold fill only has made them a bit redundant hasn’t it?

My new machine is cold fill only but the quick wash takes at least one and a half hours as opposed to my 14 year old machine’s 40 minute quick wash. I don’t see how my modern machine is saving energy!? The parts will wear out quicker too, considering each wash will generate twice the wear and tear of the old one. It doesn’t look like progress or efficiency to me.

Washerhelp Washerhelp
#5. July 24th, 2008, at 10:29 AM.


lemurtail: You make several good points.

If you can’t use solar powered hot water in the washing machine and dishwasher it seems a waste. Unless a household runs lots of baths each day it’s hard to see how you would save lots of money considering the amount of initial investment needed in solar heating because most people probably hardly use any hot water if they have a dishwasher and washing machine.

I know that apart from baths and showers, our household hardly uses any hot water from the hot water system, and in fact heating up a massive hot water tank each day just to use several litres of water is a waste. I tend to agree that water should be heated up at source – just the amount needed and nothing more. A large hot water cylinder can hold over 200 litres of water. What’s the point of heating up all that each day to 60 degrees only to use a couple of bowlfuls at most?

However, solar powered hot water is still more environmentally friendly so many people will still want to convert.

It wouldn’t damage your machine to mix in a little hot water in during the initial fill process if you were prepared to go to the trouble. It should increase the initial wash water temperature and in theory the washing machine would use a little less energy. However, it could use more water because most people would need to run off a fair bit before seeing any hot water due to cooling in the pipework. Then all the water you run off plus the water that goes into the washing machine will need replacing in the hot water cylinder (unless you have a combination boiler).

In this scenario this would cool down the hot water in the cylinder as all the water used is replaced by cold water from the tank in the loft. This would trigger the immersion heater to heat this water back up to temperature causing extra energy usage that goes towards cancelling out the lower energy used by the washing machine. Hot and cold water fill washing machines always heat the water. Many people mistakenly believe they don’t but they always still use the heater and it’s all controlled by thermostats so no over heating can occur.

The points I’m making are pretty general. There will be lots of people where this doesn’t apply exactly as some may have shorter pipe runs and experience less cooling in the pipes and some may use combination boilers etc. but the average UK user still uses a gravity fed how water system as described and washing machines are designed to run efficiently with that system.

A further point on this topic is that if you make the initial water intake to hot it can interfere with the efficiency of biological detergents which work best when used in cold water that’s heated slowly. Anything over 40 degrees is bad for biological detergents as it kills off the enzymes.

Some washing machines have 30 minute quick washes still. Economy washes take longer to wash because they use less energy heating but need to spend longer allowing the detergent to work as explained here – Economy settings take much longer – why?

Jacky Jacky
#6. July 29th, 2008, at 6:09 PM.


Howdy again. I’ve now found a (rather expensive) German device called the Alfamix, which is a smart mixer installed outside the washing machine. A manual in English can be found at http://www.solarlink.de/PDF-Files/Alfamix/ALFABedienA4English.pdf
and a flier at http://www.solarlink.de/PDF-Files/Alfamix/ProspektEnglish1.pdf

The blogger at http://www.grumpyoldman.be/batteries-not-included/ seems to like it, but I wonder what you think? Clearly it would still need very short coupling or one would have to run off contents of the feed pipe first. (I’ll be using a combi – and anyway hope to tee-off mains pressure solar hot water before it even reaches the combi).

Also, did I rightly understood the second bullet point in your article, about warm fill undesirably shortening a machine’s cycle? So the washing machine starts timing from the moment the correct temperature is reached?

Washerhelp Washerhelp
#7. July 30th, 2008, at 10:57 AM.


Hello Jacky: I think for most people such a device would be pointless because when the washing machine calls for water on the initial wash it only asks for about a bowlful of water. By the time hot water starts to run through the valve (in the average situation) the washer will have virtually stopped filling.

All that will happen is that the pipework between the hot water cylinder or boiler and the washing machine will get the most hot water drawn into it and this water will sit in the pipework and go cold. Plus if hot water is supplied via a hot water tank then all the water drawn into the pipework will be replaced by cold water from the storage tank cooling down the water in the hot tank and possibly triggering the boiler to top it back up to temperature.

Washing machines usually impulse on after reaching temperature, if not instantly at least after a set time. If you supply a cold fill machine with hot water I would expect it to reduce wash efficiency. Ultimately these machines are designed to use cold water and they have achieved A wash efficiency ratings by washing slowly and thoroughly using small amounts of cold water heated up slowly.

This issue of using hot water efficiently in the home needs a complete rethink regarding how we heat up water. For one thing, why are none of the internal hot water pipes lagged to slow down the wasteful cooling of water in the pipes?

Astrand Astrand
#8. November 19th, 2008, at 9:17 AM.


I don’t think we should dismiss these kind of solutions just due to the “average” situation. Clearly, there are cases when hot fill solutions makes sense. In my case, I have a Geothermal heat pump with a COP of 5.03 just a few meters away, so it only takes 20% of the energy to heat water with the heat pump, compared to heating it in the washing machine. Most of our pipes are lagged as well, and those that aren’t will just act as radiators, thus contribute to the heating of the house.

I think that the Alfamix device looks interesting, but it’s too expensive: Even if the claimed 300 kWh savings per year is true, it will take something like 7 years before break even, with our current energy prices.

I’m considering a simpler solution: A mechanical thermostatic mixer valve that will always provide the washer with water of a temperature of, say, 25 degrees. This should be cold enough for efficient rinsing etc, but heating from 25 to 40 will consume much less energy than heating from 10 to 40 (or whatever temperature that cold water has). Of course some energy will be wasted due to consuming more warm water than necessary in the rinsing, but as long as the cold water usage is less than 5 times the hot water usage, you should save energy.

Washerhelp Washerhelp
#9. November 20th, 2008, at 5:34 PM.


Astrand: I agree with your point that there are cases when hot fill solutions makes sense and have said so several times. The problem is that unless it is commercially advantageous to offer these solutions it will never happen. It isn’t realistic to expect manufacturers of any product to redesign and make their products more expensive than the competition in order to please a minority of customers. But as more and more people start to use environmentally friendly methods of heating their water the commercial advantage for manufacturers to redesign their washing machines in order to utilise this hot water increases.

Current thinking is that hot water costs a certain amount of money and the vast majority of people would benefit from simply heating up the exact amount of water that the washing machine requires. Until enough people are using free or very cheap environmentally friendly hot water supplies this is not a likely to change.

I agree about not investing in something likely to take seven years to start producing savings. There is a fair old chance that seven years from now washing machines will be quite different and may even use cold water only to wash.

As you point out, using hot water all the time will counteract some of the savings in heating the wash water. I’m not sure how much potential savings can be gained by heating from 25 to 40° of just several litres of water compared with the wasting of possibly 20 L of hot water being used during all the rinses.

Deter-gent Deter-gent
#10. December 9th, 2008, at 3:49 PM.


For some years I’ve used a hot-cold fill washing machine. I had two pipes connecting to the machine but each has aa tap which I turn on hot at the outset and after the wash starts, I switch to the cold supply.

This ensures the machine has very little furring in the heater, which would lead to less efficiency in the heating and consequently more cost to heat the water. (I use a gas heater for the water and although I live in the London area have had no problems with scaling)

For me the only answer is to place a Y connector to supply both hot and cold water and then switch the required tap as before.

I can easily turn the temoerature of the Hot water to the required heat level, so dfeel there shuld be no problem with the arrangement.

Deter-gent Deter-gent
#11. December 10th, 2008, at 12:04 AM.


PS. I’m told by an American internet friend that pretty nearly all washing machines in the States have Hot and Cold fill

Jillian Jillian
#12. April 4th, 2009, at 10:44 AM.


can I just add some hot water to the drum before turning on the washing machine?

Jillian Jillian
#13. April 4th, 2009, at 10:46 AM.


See above, I do this all the time (add hot water to the drum before starting the wash cycle)

Washerhelp Washerhelp
#14. April 4th, 2009, at 2:56 PM.


Hello Jillian: Yes you can but if you have to run the water for a while before it gets hot and you don’t use that water for something then you are wasting water.

Also, for anyone with a hot water tank in the airing cupboard, or with their boiler not close to the washing machine, by running the hot water to put into the machine they will have drawn x litres of hot water into the pipework which probably will just cool down and get wasted. In such cases it’s not really saving anything.

David Smith David Smith
#15. June 23rd, 2009, at 1:06 PM.


See how I do it here
http://www.solarfriend.co.uk/machines.html

Alissa Alissa
#16. July 29th, 2009, at 9:36 AM.


Hi there, I have a Samsung washing machine. The machine has a “Water Supply” button on it, where I have to indicate whether the water supply is hot or cold, when I do my washing.

I’ve connected the washing machine to a tap, however I’ve just discovered that it’s a hot water tap, not a cold water tap, and I have no alternative except to use this tap (I don’t own the cottage I live in; I rent, so therefore can’t make changes to the plumbing etc). I live in a cottage with a geyser which is very far away from my washing machine. It takes a few minutes for the water to heat up in this hot water tap.

These are my two questions:

1) If I’ve indicated that my water supply is “hot” on the machine, will this affect how my clothes are washed, as cold water is actually filling the washing machine initially as the water hasn’t heated up yet?

2) Will the water used to rinse my clothes be hot or cold? Will the water have cooled down in the pipes by the time the rinse cycle is on? I’ve heard that it’s good to rinse clothes in cold water, not hot, but my washing machine is connected to a hot water tap. Fortunately, my machine has the option for receiving a hot water supply, so it’s not as if I’m filling a cold fill machine with hot water. I only have one water supply valve, though, so I don’t have two separate valves where hot and cold water can flow in separately, and I’m not sure if this is a problem?

Please advise how I should proceed in using my washing machine. (It’s quite an old machine – bought in 2003, although it was only used for a couple of years. I then got a frontloader, but it’s broken, so I’m reverting to my top loader). It’s quite a basic machine, and there are no temperature settings really that I can see.

Should I be concerned about the hot water supply? I would have preferred a cold water supply as I’m used to doing my washing this way, and I’m not sure how clothes are washed with only a hot water supply. Thanks.

Washerhelp Washerhelp
#17. August 1st, 2009, at 12:12 PM.


Alissa: I’ve not heard of such a button before and can’t imagine why any manufacturer would allow you to only use hot water because the washing machine can’t control the temperature of this water. I can’t see how a washing machine could work connected only to a hot water supply for the reasons I listed in this article.

As the hot water temperature in our supplies are usually at least 60 degrees centigrade how could you do a 40 degree or 30 degree wash? It would ruin woollens and badly crease laundry as well as shrink some. It would kill the biological enzymes in biological detergent reducing its effectiveness an would waste loads of hot water and energy.

If you are renting the house the landlord surely has a duty to provide a means for you to use a washing machine so you need a cold supply plumbing in.

Alissa Alissa
#18. August 1st, 2009, at 4:43 PM.


Hi there,

Thanks for your answer!

I’ve managed to make another plan regarding my washing machine. I had a feeling connecting the washing machine to a hot water tap wasn’t a good thing to do. Glad you confirmed it. I’m not sure why my landlady has only a hot water tap in the laundry room she said I could use. Very odd!

Alissa Alissa
#19. August 1st, 2009, at 4:48 PM.


I’ve placed my washing machine in my kitchen, however, it’s a top loader, and there’s a marble counter top above the washing machine (that’s why I didn’t think I could put my washing machine in my kitched originally – see above post). I now have to pull out the washing machine every time I use it. I’ve bought castors, and will be placing the machine on them. I just hope it’s safe to use… do you know if it is OK to put a washing machine on castors? I bought them at a hardware store and they look pretty stable…

Washerhelp Washerhelp
#20. August 1st, 2009, at 5:47 PM.


It’s impossible to say without knowing what they are like and how they are being fixed but if if they are the kind that are designed for appliances to stand on it should hopefully be OK.

Alissa Alissa
#21. August 3rd, 2009, at 8:00 AM.


Thanks very much for your help!

Tim Tim
#22. October 7th, 2009, at 4:01 PM.


Been planning on using a thermostatic tap when I return home and fit a solar system. Thanks for some invaluable information clearly explained. I shan’t be connecting up the plumbing now!

louise louise
#23. November 6th, 2009, at 2:38 PM.


I have just proved what I suspected… that my partners cold fill AEG has been connected to the hot water pipe by accident for 4 years because the blue (cold) plastic lever was on the hot pipe and visa versa. Will this have done any damage to the machine?
when it was opened at the end, the washing was steaming!

I’ve changed it over now.

Washerhelp Washerhelp
#24. November 6th, 2009, at 5:15 PM.


Louise: Glad this article helped. It’s not uncommon for that to happen as I said in the article. No damage should have been done to the washing machine, just a lot of wasted hot water and extra ironing will have been needed, maybe even shrinkage caused to clothes.

Alan Alan
#25. December 4th, 2009, at 5:52 PM.


When we had our solar panels fitted the plumber removed the cold water header tank and fitted a pressure regulator on the feed into the hot tank. So now our hot tank fills straight from the mains and the hot pressure is only a tad lower than the cold. We were told that this is now standard practice.

We are just getting rid of a 16 year old hot and cold fill machine and replacing it with a cold fill only one, having contacted all the manufacturers I could think of and being told all machines are cold fill only. I have been holding on hoping that as the number of people with solar panels increases one of the manufacturers will have the foresight to see that there is a market for a machine that intelligently mixes water to the correct temperature, but the old machine has finally died so I’m forced to make a purchase.

It’s all very well manufacturers quoting these wonderful efficiency ratings but any machine that heats cold water when there is surplus hot water available is extremely wasteful. Also I understand the efficiency ratings are based on low temperature washes. Anyone who cares about the environment wouldn’t put bological washing chemical down their drain, so would need to use a higher temperature wash.

Washerhelp Washerhelp
#26. December 7th, 2009, at 1:40 PM.


Hello Alan. It would be nice if washing machines were sophisticated enough to perform optimally by adjusting how they work according to the environment they are placed in instead of being designed to work optimally for the average customer only. Being able to configure the washing machine by telling it whether we are using biological detergents or not, whether we are using solar heated hot water or a combination boiler or an immersion heater tank upstairs etc. might be better.

However, it’s not accurate to assume that using cold water only is always inefficient as my article describes in detail Should I buy a cold fill washing machine or hot and cold fill?. As this article describes, in circumstances where the hot water to the washing machine is supplied via a hot water tank a long way from the washing machine it can be very wasteful to use hot water.

The point is though that cold fill only washing machines are only “better” for a customer using hot water from a hot water tank upstairs and using biological detergents and doing mostly 40 degree washes. There must be a substantial number of customers where this scenario is just not the one they are using which is why with so much focus on efficiency and energy saving many would prefer washing machines to be designed to always be the most efficient for all customers.

Daisy Daisy
#27. December 11th, 2009, at 12:23 PM.


Hi

I have been reading this thread with interest and hope someone can help.

We just had a cold fill only machine fitted, the previous one was hot and cold fill. However, the hot water pipe had no cap and no lever to turn it off, so we connected to the hot water supply instead of the cold.

The main thing I am concerned is the temperature being too high to start with if I am only doing a 30 degree/40 degree wash. To stop this, could I turn down the temperature of the water on the combination boiler? There is an option to do this I believe, but would it solve the problem or am I better to get the hot water pipe capped and then connect it to the cold pipe/valve as it was meant to?

thanks
Daisy

Washerhelp Washerhelp
#28. December 11th, 2009, at 8:34 PM.


Daisy, you need to get the hot supply capped off and use the cold water supply for the reasons I list in my article. It’ll work out cheaper in the long run even if you pay a plummer as you are wasting all that hot water each time you wash.

daisy daisy
#29. December 13th, 2009, at 3:01 PM.


hello

I understand that but as a temporary solution, would turning the temperature down on the combi-boiler to 30 degrees work?

Washerhelp Washerhelp
#30. December 13th, 2009, at 6:27 PM.


That would make sense Daisy. Or turn the temp right down when washing.

Bournetoride Bournetoride
#31. February 28th, 2010, at 8:12 PM.


Alan
There is a machine suitable for solar heated water, the Electrolux (REX) Sunny, alas it seems to be sold only in Italy where solar heating is more prevalent.
Its not rocket science despite Washerhelp’s objections, when the”Solar” button is pressed hot water mixed with just enough cold to achieve the desired temperature for pre-rinse and main wash. Cold only for rinses.
The net result is that the hot water pipe is flushed of cold water during the pre-rinse and hot water is used for main wash.
The cold water that refills the hot tank will be replaced by more solar heated water on any sunny day.

Washerhelp Washerhelp
#32. March 2nd, 2010, at 9:01 PM.


Bournetoride: The article advises not to connect the hot water hose directly to the washing machine as it would result in all the problems described in the article.

It isn’t about washing machines designed to use solar heated water or even attaching a thermostatic valve to mix hot and cold water. The article is only responding to people asking if it’s OK to just connect the hot water directly to the washing machine’s cold only fill valve.

 

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