I get a lot of queries from people who’ve discovered modern washing machines are cold fill only but still want to use their hot water supply. Many are very frustrated because they may have a “free” hot water supply where maybe their hot water is included in their rent, or they have invested a lot of money in a solar powered or otherwise eco-friendly hot water supply and are furious that none of their domestic appliances use hot water any more.
You can’t just connect the cold fill washing machine to the hot water supply instead of the cold because of the reasons in this article – Don’t connect a cold fill washing machine to the hot water tap. However, some people are thinking laterally and wondering if they could connect the hot and cold fill hoses to the washing machine using a y-connector so the washing machine would receive a blend of hot and cold water. (This is an alternative genuine Hotpoint y-piece hose connector which is more expensive but possibly better quality. Both will fit any UK washing machine fill hoses)
All I can say is that theoretically this could work, but without a thermostatic control valve it would be difficult to get the mix right so the washing machine only ever received “warm” water. If the washing machine received water which was too hot then the problems mentioned in my article (linked to above) would come into play.
Cold water works better with biological detergent
Also, cold fill washing machines are designed to perform better when using biological detergents or detergents designed for low temperature washes. They start from cold water and slowly heat it up, which manufacturers claim gives better wash results. If you supply the washing machine with water already heated it could affect wash results by not utilising biological detergents optimally or by potentially speeding up the wash time. This latter point sounds great, we are all frustrated with how long washing machines take to wash these days, but wash efficiency could be compromised if the wash time is artificially increased because some detergents need a long time to do their job properly.
So the answer is yes, but you would need to ensure only warm water entered the washing machine and ideally not too warm. If the cold water pressure dropped because of a problem with the supply or because of someone drawing off cold water elsewhere any delicate balance would be disrupted and potentially very hot water could enter the machine and damage delicate laundry. So without a thermostatically controlled valve it might be a bit hit and miss.
Are there any advantages to warm water being used? Potentially, it’s been suggested that rinsing in warm water may give better results.