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.
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
Fixed-price repairs, Pay monthly, Repair & protect your whole appliance..
50% off annual membership
Subscribe to Which? today and save 30% on Digital Annual subscription for your first year. Offer ends 18.03.24. This offer is only available for new Which? annual subscriptions (excluding Gardening, Travel, Computing or Money packages).