Can you connect a dishwasher to the hot water supply?

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.

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.

Pros –

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.

Cons –

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

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49 thoughts on “Can you connect a dishwasher to the hot water supply?”

  1. I’m not sure if this thread is still active: the water heater on my Zanussi dishwasher has given up and it only washed cold. Rather than scrap it and spend a small fortune on a new dishwasher I connected it to the old (and redundant) hot water feed for the washing machine that was close by, the water inlet temp is around the 60°C mark and it seems to be working fine. My hot water is heated in summer by off peak electricity and during the winter by a back boiler fitted to the woodburner, so hopefully I will see a saving in my fuel bills as well askance more having clean dishes.

  2. I have a indesit dishwasher and brought a y fitting to fit my washing machine and dishwasher to the cold pipe feed , and its very annoying as the hot pipe feed valve is just above the cold one and the valve is in the way !!!!!! I have a combi boiler and would love to put the dishwasher into the hot feed pipe and then my issue is sorted in theory , but could I do this with a indesit dishwasher , as when I research it , it states and advice not to do it its very annoying to the point of no washing is getting done and a dishwasher that’s sitting doing nothing . Please help thanks xx

  3. I thought I would state the reason for the cold water supply. The EU energy labelling scheme has caused this need for cold. It’s based in the fact that most people’s incoming cold water is a similar temperature. Hot water is produced by individual household with varying carbon footprints and as such would be impossible to provide a energy rating based on that, so cold water is used for the calculation purpose only, therefore forcing the machine to heat up water from cold.
    I have solar thermal at home and am about to connect the dishwasher to a 40deg C Feed. This will improve the efficiency of energy use as the temperature difference is less and it will use less electricity for the top up to 50 or 69 deg.

    1. Cold water boils faster than hot water. Therefore, I would believe cold water running to your dishwasher would do the same. …physics

  4. I have noticed that some dishwasher manufactures are marketing their machines as suitable for warm water inlet up to 60C (one at 70C). We have solar panels and have a device that directs ANY surplus solar energy to the hot tank. For full benefit a large hot tank (which doesn’t have to pressured) is needed. The only qualification seems to be that glass ware can become tarnished at higher temps – we use hand washing for these.

  5. Most home hot water cylinders are set to temps below 60C (55C is recommended to avoid water based bacteria surviving) , so dishwashers would suffer no harm. Unless you have the boiler constanting heating the water to the desired temp, its likely the hot water is much closer to mid 50C that whatever the tank cylinders thermostat is set to. Most eco settings on dishwashers is 50C. I would be very surprised if any solar thermal or even PV electric to cylinder heater would be the only source or heat and apart from the peak summer, heat the water anywhere close to 60C (unless you have a massive solar array). At dusk that solar heat is already dropping. Would most cold water often not come from attic tanks and in the daytime be heated anyway? Heating water to 50C+ or 40+(washing machines) not require large amounts of power. Hence we are all told to wash clothes at 30 (or less) and use the 50C eco setting on the dishwasher.

  6. We have a Belling Dishwasher model number BELFDW150, bought 2017, on a cold fill.
    We have solar water heating, which raises the temperature in the hot water tank. We have to heat the hot water tank on occasion, so we can have a lot of hot water.
    We have a plug-in electricity usage monitor which shows the dishwasher uses 27p of electricity on a 30 min cycle and 26p on the Eco cycle.
    We also have a washing machine with a hot and cold fill. When the hot water tank is hot, the normal cycle costs 9p. When we turn off the hot feed and use cold only, it costs 22p.
    I rang Belling today and was advised we can use a hot fill into our dishwasher model.
    Hope this helps.
    Many thanks for running this very helpful site.

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