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 washers
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louise says
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 says
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 says
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 says
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 says
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 says
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 says
hello
I understand that but as a temporary solution, would turning the temperature down on the combi-boiler to 30 degrees work?
Washerhelp says
That would make sense Daisy. Or turn the temp right down when washing.
Bournetoride says
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 says
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.