In theory yes, but the way washing machines work means that in the majority of UK households it’s likely to be more economical to use a cold-fill washing machine.
It does depend on how close the source of hot water is to the washing machine, but a substantial percentage of households in the UK get their hot water supply from a hot water tank upstairs, and this experiment demonstrates the problems with that. Note that even combination boilers take a long time to start supplying “hot” water.
I have previously written in greater detail about this subject (links at the end of this article), but I wanted to carry out this experiment to demonstrate the argument in a very simple way.
Here is a visual demonstration of how hardly any hot water gets into a modern washing machine, and therefore, why a hot water valve isn’t necessary for most people.
Wasted Water from Hot Tap
The photo above shows how much water was drawn from my hot water tap in the kitchen right up until it started to run hot. So this is basically a bowlful of cold water.
How Much Water is Used on Wash?
The photo above shows how much water was pumped out of my washing machine at the end of the wash section. If you compare it with the previous photo, it’s only got a little bit more water in it.
Most wash cycles typically only use just under a bowlful of water on the main wash (I used Cotton’s 40°).
This means if I’d been using a hot and cold fill washing machine, then by the time it had drawn in the amount of water needed (second photo), there would be little more than a few cups full of hot water in the drum.
In fact, in my case, the washing machine would have had to fill up entirely with the hot water valve in order to just get a splash of hot water right at the end.
This shows that unless you can get hot water running through the washing machine hose within several seconds, you will not get any useful amounts of hot water into the drum at all.
There are other problems explained in my related articles (below) such as wasted hot water in the plumbing pipework and hot water already in the hot water cylinder being cooled down with replacement water.
There is a belief that using hot water in a washing machine is more economical, but it’s not true in the overwhelming majority of cases. One reason is demonstrated in this article. Another is that washing machines are not sophisticated enough to properly utilise hot water with such a variety of delivery methods and with totally unpredictable lengths of time before hot water reaches the washing machine. This is also explained in detail in my previous articles.
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