Tankless water heater + new dishwasher = ???
April 2, 2016 10:20 AM   Subscribe

I have a tankless water heater (a Takagi T-K Jr.) and am in need of a new dishwasher. The dishwasher we're replacing is an old (at least 15 years old if not more) Maytag with a heating element and it's always done a sufficient job. I was planning to replace it with a Bosch, but just learned that new Bosch dishwashers don't have a heating element...so I'm wondering if the water will get hot enough to clean the dishes.

I've talked to salespeople at two appliance stores, and neither seemed very confident in their "I don't think it will be a problem" answers (tankless water heaters are not common where I am in the midwest US). Bosch customer service said the water needs to come into the dishwasher at 120 degrees and they hadn't heard of problems with tankless water heaters...but I don't want to make an expensive mistake. And People on the Internets have reported problems. So, I would love to hear real life stories from people with tankless water heaters and newer (water/energy efficient) dishwashers. Do Bosch dishwashers draw water for long enough that the water from a tankless heater will get hot enough? Should I focus my search on dishwashers with heating elements instead? Any brand/model recommendations? Many thanks!
posted by Empidonax to Home & Garden (6 answers total) 1 user marked this as a favorite
Best answer: Bosch dishwashers don't have a heated drying element. They heat water just fine.

In fact, we have a one-year-old Bosch Ascenta and a tankless hot water heater. What I've done to avoid the short draw problem (this is not specific to Bosch, any efficient dishwasher will be the same) is just to hook the dishwasher up to cold water and let it heat its own water. It does take a little longer (maybe an additional hour if the inlet water is very cold), but it works just fine and I'm sure it is much more efficient than all those short draws. This is the standard way to hook up a dishwasher in most of the rest of the world and I highly recommend it with a tankless water heater.
posted by ssg at 10:31 AM on April 2, 2016 [3 favorites]

We bought a Bosch three years ago and hate it. It kept leaving bits of food in the glasses on the top shelf, but because of the drying process the food was caked on. We had Bosch out 8 times in the first year, and they kept saying that our water wasn't hot enough and wouldn't replace it. Yet when they tested the water it was above 120 degrees. Now I just make sure everything that goes into the dishwasher has no bits of food, otherwise I'm manually rewashing all the glasses. So my recommendation is not to get a Bosch.

That said, I just put in a tankless water heater 2 months ago and have had no problems with anything. The dishwasher operates the same as before.
posted by herda05 at 10:00 PM on April 2, 2016

Many (most?) dishwashers just use cold water and heat it themselves. How you heat the house water should not matter to a dishwasher.
posted by bonehead at 11:22 PM on April 2, 2016

Best answer: The Bosch SilencePlus 44 we bought back in 2013 has been totally awesome.

We do NOT have a tankless water heater, but our hot water is only about 125 degrees and there's at LEAST a 30 foot section of 1/2" pipe, so a third of a gallon of coldish water starts most wash loads. The Bosch unit we have uses about 2.3 gallons per load IIRC. We do not run the water at the sink or do anything else to warm up the water prior to running a load.

According to this blog post the Bosch units all have the ability to heat water. I know if you open ours early in the cycle it lets out this huge cloud of very warm steam, a lot hotter than our water heater generates.

We tend to run the dishwasher somewhat frequently and we use the Finish Quantum Max pods. It is very unusual for dishes not to get very, very clean, and usually when something goes awry, it is because something tipped over and collected a puddle of water.

I did a lot of research on dishwashers before selecting ours. There's a huge amount of variance in quality and satisfaction with the various units, and I have a suspicion that careful research is a much more important factor in the result than water temperature.
posted by jgreco at 7:07 AM on April 3, 2016

Best answer: Yes, Bosch dishwashers have a inline water heater - that is the only way they can reach the sanitation temperature. They don't have the ridiculous exposed heating element for drying like many American models do. Incidentally this means that there are no top rack restrictions in such a dishwasher, anything can go anywhere.
posted by werkzeuger at 9:10 AM on April 3, 2016

Response by poster: Thanks all! A second call to Bosch customer service and your answers have put my mind at ease. I suppose I shouldn't be so surprised that a big-box store salesperson gave me false information (he told me that the dishwasher wouldn't heat the water - that it just relied on the water heater to heat the water). Dishwasher has been ordered!
posted by Empidonax at 10:58 AM on April 4, 2016 [1 favorite]

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