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.
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
Oliver Shaw says
Hi andy,
Personally I feel it may be better connected to the cold supply, as you say the hot water will bake proteins on and shorten the wash cycle so results will be compromised!
Our Tecnik (economy Bosch) says you can connect to a hot supply below 65 degrees, but do advise against it, also the economy 50 cycle would be rendered usless! And the pre rinse only cycle would be hot and bake foods on while waiting for a full load to collect.
The fill hose situation, the cold ones are a plastic type material, but the hot ones should be a form of rubber. Our old Bosch dishwasher said if connecting to the hot supply, you need to send away for a special rubber fill pipe before doing so, but that was a long time ago. Whether there is any difference today I would not know. I have hot and cold (red and blue) fill hoses on my washing machine and they appear to be identical except for the colour! The difference in material me be internally though. The hot one may have a slightly larger bore for improved flow rate. Although my washing machine is connected to a cold supply using a “Y” adaptor. But the dishwasher is connected to a cold supply aswell, and the results aren’t perfect, but I feel that may be the dishwasher being a cheap job opposed to anything else, we use a good quality detergent, Finish.
HTH,
Oliver.
Dave says
Miele recommend using hot fill for their dishwashers and Hoover also recommended it for their (now discontinued) HD97 triple A rated model which was on sale in 2003 – 2007.
I have a Miele which uses hot fill (and has done since new) – the wash time for a 75 degree “sensor wash” is 1h35 mins when the water going in is at 65 degrees; if I happen to have drawn a lot of hot recently and the cylinder has not recovered the wash time increases to about 1h55 / 2h when the water is around 30 degrees going in.
Wash results using Ecover tablets and Ecover rinse aid are superb whatever the inlet temperature. I did try using vinegar instead of rinse aid, as recommended by Miele, for environmental reasons but I have to admit that the results for glasses were poorer.
The pre rinse (which I rarely use – and Miele recommend NOT using unless your pots are very dirty and to be left for a long time, again for Environmental reasons) is hot of course, but I have never had any problems with anything being baked on. Indeed using the hot pre rinse seems to shift things better than my old Bosch dishwasher ever did on a cold rinse, although that was 18 years ago and at that time I understand the Bosch machines were made by Hotpoint, who we know are not especially highly rated.
I would highly recommend hot fill for any dishwasher – it certainly saves vast amounts of money and time.
Oliver Shaw says
I though Bosch made Hotpoint machines?
18 years ago Hotpoint made excellent machines, it is only recently mainly since the Merloni take over has the quality some what dropped, maybe now should be called “COLDBLUNT”!!!
Also tried Ecover and found it to not be half as good as Finish, your experience is interesting to find that it works! Tried their laundry powder and had to rewash the entire load using my normal biological Ariel and a long 60 wash. Things did not even smell clean, and my work clothes came out asdirty as when they went in.
So perhaps having a dishwasher connected to the hot supply is not such a bad thing provided the water is not too hot. Particulally if like you Dave you have a free hot water supply. We could do with free hot water, but cannot fit solar panels due to our house being a listed building.
All the best,
Oliver.
Washerhelp says
Oliver, Hotpoint are owned by the same company that makes Indesit. Bosch are made by the company that makes Siemens ( Who owns who? Who really makes your washing machine? )
Regarding Ecover detergent, they didn’t do too bad on Which? dishwasher detergent tests, “This Ecover tablet is the best dishwasher detergent we’ve tested which has ecological claims.”
Which is the best dishwasher detergent?
Anonymous says
Andy,
I know that, many many years ago Bosch did make dishwashers for Hotpoint, it is a hell of a long time ago though. This hasn’t been the case for many years now, Merloni make everything for Merloni, not buying badged up machines like Hotpoint did.
Regarding Ecover, useful as a snooze button on a smoke alarm IMHO!!!
HTH,
Oliver.
Dave says
Not been back to this page for ages and only just seen the comments re Ecover.
I’ve got to say that I use ecover washing powder, Fabric Softener, Dishwasher Tablets and Rinse aid and they are all actually very impressive.
The washing powder works far better than Persil or Fairy non bio ever did either in my old Hoover washer or in my new LG. I do have to use it sparingly though as it is very sudsy. The fabric softener is good, but I must admit that I am not a big fan of fabric softeners anyway, so I don’t have a lot to judge against except Waitrose’s own brand which I used to have before Ecover. I can’t tell any difference between that and Ecover.
For dishwashing I used to use Finish, but it Finished off all my glasses and some of my better crockery as it is so very abrasive. To be fair it does carry warnings that it may affect your dishes and glasses and many comparison web sites and reviews such as Which? also warn that most traditional dishwasher detergents can do this. The Ecover tablets work pretty well and my glassware is nice and shiny, rather than looking like it’s been sprayed with a thin coating of PVA glue. The only thing that the Ecover tablets don’t seem to deal with is baked on mincemeat when I make mince pies and they boil over onto the baking tray; but Finish never touched that either. A good old Brillo pad and a sink full of red hot water seems to be the only way to deal with that one.
Ecover Rinse Aid looks, smells and seems to behave like Finish, Co-op’s own brand and Waitrose’s own brand to me. In fact it was because they all seemed the same that when I read in the Miele book that vinegar does the same job but is cheaper and kinder to the environment that I thought I’d try it, but I have to admit that it didn’t seem to do such a good job. I’ve also had a free bottle of Miele’s rinse Aid, which seemed to work fine but it looked just like tap water! Heaven knows what was in it.
It’s interesting to see the comments about Hotpoint and Bosch’s relationship: in my old Bosch dishwasher instruction book I remember clearly that it stated that for service you had to ring Hotpoint, hence my assumption that it was Hotpoint doing the making. I also recall that I bought that dishwasher from the Co-Op and they had the identical machine in at a lower price with the Hotpoint badge on it and also their own brand which was also identical on the outside but inside had grey baskets not white. This was back in 1988 and that machine really was utter rubbish. It was the worst ever buy that I have made in terms of electrical appliances. In fairness it was a slimline model and I don’t think that helped as I have heard many people say since then that slimline models don’t tend to work as well as full size, but even allowing for that it was a bitter disappointment and I got shut after a very few years, going back to hand washing my pots for about a decade before getting a Hoover dishwasher in 2003, which proved to be very good at washing but very unreliable (what do you expect when it’s a Candy in disguise – it even had Candy labels on the circulating pump and some of the electrical components in it) and then the Miele that I have now in 2007.
The old Bosch-Point that I had also had provision for hot fill I recall. Of course back then I didn’t have solar water heating but as it was going in a space where a washing machine had been I did connect it to hot water tap that was already there. The instructions for doing so consisted of telling you to undo the water inlet hose from the back of the machine, use long nosed pliers to pull out the strainer, then remove a small rubber pressure reducing device, put the strainer back and connect up. I did all those things but the machine would not operate as the hot water pressure was too low (back then I also had lead hot water pipes which were all furred up and had a very tiny bore!), so I had to put the rubber part back and use cold anyway.
A colleague of mine at work has just moved into a new house and has room for a dishwasher now so he’s been looking at them. He has a 12 year old Bosch washing machine that is still hot fill and he was horrified when he found that Bosch don’t do hot fill dishwashers as such, but after referring him to this site he went and downloaded the instruction manuals for some Bosch dishwashers that he is considering and is now quite happy to find that they (apparently – I have not verified this myself) state that hot water fill is OK. He’s very brand-loyal to Bosch so he was keen to get one of theirs if he could possibly use hot water.
Oliver Shaw says
Hi Dave,
You can still connect a Bosch dishwasher to a hot water supply.
I have had no luck with Ecover at all, their laundry powder was rubbish from what I could tell, not even a tenth as good a Ariel bio powder or Persil bio powder.
We use Finish detergent, salt and rinse-aid and find they work a treat, like you say burn’t on food needs a helping hand, such as Fairy Power Spray, then everything comes out clean.
We had a Bosch slimline Dishwasher, funnily enough bought in 1988 (the year I was born), and it was excellent, it got everything clean, even with own brand crappy detergent. So maybe yours was a bad one!! It was far better than modern Bosch. I have a 15 year old Bosch washing machine and thats also excellent, shifts all stains and muck perfectly.
Oliver.
Expertcat says
Did you know that most manufactuers dont recommend the tablets.
As I have found out the consumers still put in salt and rinse agent and with the 5in1 tablets (which has them all in) and so the machine will generate excess foam which causes water friction inside the machine hence poor washing of dishes.
The tablet idea is consumer led by the manufactuers of the detergent.
Just think if the machine was made to take just tablets would the manufactuer of the appliance still put in rinse aid and salt regeneration units the answer would be no so in therory the appliances wouls become cheaper.
Washerhelp says
You make a good point Expertcat. I use 3 in 1 tablets with good results but we don’t use dishwasher salt or rinse aid.
Oliver Shaw says
Hi Andy and Dave,
On the strength of what I have read on here and Daves experience I have put the crappy Tecnik on Hot fill only. Well the first thing I can say is it is not such a crappy Tecnik after all! It now does a pre-wash in hot water instead of cold, so there are no more grease blockages forming, the dishes are coming out spotless and the machine (now 4 years old or so) smells fresh. It has a regular monthly cleaning with Finish dishwasher cleaner, but still smelt, now on Hot fill the food is broken down from the off so nothing can vegitate inside the machine.
As it is an economy version of a Bosch there is no intensive wash cycle, just a “Normal 65oC” and “Economy Wash 50oC”. and the “Pre Rinse only”. None of these use the heater in the pre wash, so it was cold, all the grease built up inside the machine and made it smell, and as the soiling was not being softened by a warm prewash, it used to get baked on by the hot main wash. Not any more, our hot water is about 40oC just the right temperature for a “biological prewash”, the grease and proteins are broken down before the main wash can begin by the Finish powder which is biological, so no more dirty pans or hand washing either.
The new programme sequence for a Normal wash is:
Prewash (40oc incoming water temp.)
Mainwash (65oC heated by machine)
Rinse 1 (40oC incoming water temp.)
Rinse 2 (40oc incoming water temp.)
Final Rinse (70oC heated by machine)
Drying.
The new Economy wash sequence is:
Prewash (40oC incoming water temp.)
Mainwash (50oC heated by machine)
Rinse 1 (40oC incoming water temp.)
Final Rinse (65oC heated by machine)
Drying.
The Prewash only cycle is now 40oC but we rarely use it as the dishwasher is on once or twice a day.
It is like having a new dishwasher, it actually does it job properly and in less time, it has gone from 2:30 to 2:10 for a normal wash. Haven’t tried the economy wash yet but was the same length a normal.
I was very wrong to be sceptical of this, the only problem was fitting a “Y” adaptor to the washing machines hot supply so they could both use hot water, but all works and no leaks. I have to say there are for me no negative points, only a hell of alot of positive ones, everything in every respect has improved dramatically!
The manual for the machine says you can use Hot water upto 60oC (ours is never above 55oC or so but in the main about 40oC)but recommend cold – don’t know why, the dishwasher was rubbish with cold water. It washes betterthan our previous machine now and equally as good as our old Bosch bought in 1988.
All the best,
Oliver.