I’ve had several people ask if you can connect a cold fill washing machine to the hot water tap instead of the cold one. They were unhappy about the disappearance of the hot water valve in UK washing machines, and were wondering if they could circumvent the change.
Many people who are using solar powered energy to heat their water, or who had another cheaper environmentally friendly supply felt that the advantages of their environmentally friendly and economical hot water will be wasted by not using their hot water supply.
However, the answer to the question is no, for the following reasons..
Hot water supply is too hot
The incoming water temperature would be too hot (usually at least 60 degrees Centigrade). This can damage delicate laundry and shrink woollens.
There would be no way of controlling the temperature of the water going into the drum and onto the laundry.
A washing machine designed to use hot & cold water will control the temperature of the water in the drum by either filling with a mix of hot and cold – or filling only with cold water on all wash cycles except the really hot wash.
Too hot for most wash cycles
The temperature of household hot water is also too high for most commonly used wash cycles, which only need 30 or 40 degrees.
It is pointless putting on a wash cycle that needs to heat the water up to 30 or 40 degrees if the water is 60 degrees from the start.
So apart from potentially damaging some laundry, the washing machine’s thermostat would close almost immediately and the wash cycle would move on to the rinsing too soon. This would shorten, but compromise the wash quality.
Hot water not good for biological detergent
Biological detergent contains living enzymes. These enzymes are killed off at the temperature of most people’s hot water. So filling with hot water only would again compromise wash efficiency when using biological detergents.
Biological detergent is more effective when starting in cold water with the water gradually heating up.
Rinsing in hot water is very bad
If a washing machine is only connected to the hot water supply then obviously when it comes to rinsing the laundry – the water going in would also be hot.
So the laundry would be rinsed in hot water. This would cause severe creasing, as well as wasting all the hot water and being very energy expensive. Also hot water tends to activate detergent and create suds whereas cold water doesn’t and is therefore more likely to be better suited to rinsing laundry.
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What about connecting both hot and cold hoses to a cold fill washing machine?
You can’t swap the cold water supply for a hot supply for the reasons given in this article. However, there might be an argument for using a y-connector to connect both hot and water supply at the same time. However, this seems a lot of trouble for little benefit. You would need to manually adjust the water pressure of both supplies to get a balanced, “warm” combination.
But as hot water usually takes a while to run through the pipework, the chances are it wouldn’t use much if any on the wash cycle anyway. This is in fact one of the main arguments for cold fill only machines. It would do all the rinses in warm water, which may (or may not) be better. But it would also use a lot more energy.
A full explanation as to why almost every washing machine is cold fill these days is here – Pros and cons of hot and cold fill verses cold fill washing machines
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can I just add some hot water to the drum before turning on the washing machine?
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.
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.
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.
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!
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…
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.
Thanks very much for your help!
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!
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.