This article was inspired when comments from another article ventured into the subject of whether you can connect a dishwasher to the hot water supply instead of the cold. This doesn’t appear to have a clear-cut yes or no answer. There is conflicting advice, even from dishwasher manufacturers. Some claim it’s more economical but others say it’s better to run a dishwasher using cold water.
Most dishwashers in the UK are supplied with a cold fill hose and with instructions to connect it up to the cold water supply. Most people do connect it to a cold water supply and they work perfectly well. Many dishwashers are designed to work by heating up water from cold.
Some dishwashers can be connected to a hot water supply though. If so, it should say so in the instruction manual. If you do connect a dishwasher to the hot supply you should use a hot fill hose, which is designed for use with hot water. I’m not able to emphatically say that connecting a cold water hose to a hot water supply is running any risk.
But fill hoses have always come as either hot or cold. Either in red or blue, or with a red stripe or blue stripe. So the implication is that they are different in some way. If this is pure marketing spin I wouldn’t be too surprised. But it is reasonable to expect that the individual requirements for hot and cold water are different enough to require specialised hoses.
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Pros and cons of connecting a dishwasher to hot water
The next sections look at some of the advantages and disadvantages of using a dishwasher connected to a hot water supply.
Depending on how your hot water is generated, it potentially saves electricity. Dishwashers often wash at high temperatures. They also often use high temperatures for the last rinse to aid drying. However, If using hot water is so much more efficient, why aren’t all dishwashers coming with recommendations to use hot water? Why don’t manufacturers advise that cold water can be used if preferred – instead of the other way round? The answer may be very much related to the same question about cold fill only washing machines
Quicker wash times
If you can get hot water into the dishwasher efficiently, that is, it doesn’t take a long time to start running hot. Then wash times can be speeded up.
If the water entering the dishwasher is over 60 degrees it can damage the filtration system built into dishwashers. So don’t use hot water if this is the case. My understanding is that hot water should only be set to 60 degrees anyway, which is the optimum setting for a hot water supply in most homes. But some people may have set it higher.
Hot water supplies may not have the same water pressure as cold, especially if supplied through a hot water cylinder in the airing cupboard. Hot water hoses are more prone to kinking too, so you would need to ensure the hose isn’t under any physical strain at the back because when hot water runs through it, the hose can go soft and develop a kink.
If the initial water is hot it can bake some food onto plates and make it more difficult to clean.
Dishwashers often have a 50 degree wash cycle. If the water inlet temperature is already 60 degrees this programme may be compromised.
If you want to check your dishwasher can use hot water but don’t have the instruction book you may be able to download one here – download instruction manual for washing machine or other white goods appliance