I’ve had several people ask if you can connect a cold fill washing machine to the hot water tap. 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 cheaper 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.
However, the answer to the question is no, for the following reasons..
Water 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. A washing machine designed to use hot & cold water will control the potential temperature of the hot water by 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.
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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…
No good for biological detergent
Biological detergent contains living enzymes. The enzymes are killed off at the temperature of most people’s hot water. So wash efficiency would again be compromised when using biological detergents. This type of detergent is more effective when starting in cold water with the water gradually heating up.
Rinsing in hot water is very bad
The laundry would also be rinsed in hot water. This would cause severe creasing as well as wasting all the hot water and being very energy expensive.
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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
Andy Trigg (Whitegoodshelp) says
Hello rad. The biggest problem is that hot water coming into a washing machine is never instantaneous. Even with a combination boiler, if everything is set up okay, hot water can reach the washing machine reasonably quickly – but still potentially not quick enough for most settings. Any washing machine supplied with a hot water pipe that has quite a long pipe run from the boiler will take a while to deliver hot water because all of the previous hot water that had been drawn in has since has cooled down and gone cold.
With hot water supplies in the UK commonly being delivered by a hot water cylinder in an airing cupboard upstairs, this problem is even worse. It can take so long for piping hot water inside the tank to actually get to the washing machine that with today’s washing machines hardly using any water the washing machine has just about finished filling up by the time any hot water arrives.
The only way around this involves wasting water or trying to recycle it but with no room to store it . Temperature sensors on the incoming water could divert the water from the drum and from washing in the detergent until it gets to the correct usable temperature. But this water would need to be diverted to a separate container and there is definitely no room for one in a modern washing machine. Or alternatively it would have to be pumped away down the drain instead. So one potential problem is solved by causing water wastage.
So it is technically possible for manufacturers to utilise hot water intelligently and effectively, but only at the expense of wasting water, or trying to recycle the unneeded cold water in the hot pipes later on by storing it in a container somewhere inside the washing machine. It is just completely impractical to do so. So it’s either go back to hot and cold fill washing machines (that for most people means hardly any hot water getting into the washing machine) or use cold fill only and heat up just the right amount of water that is needed for the wash which is the current trend. In the great scheme of things, looking at the most common scenarios and the most common requirements it is by far the most sensible way of doing it.