Thread Number: 80699  /  Tag: Modern Dishwashers
Bosch Dishwasher not cleaning properly
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Post# 1046853   10/4/2019 at 21:14 (276 days old) by Dustin92 (Jackson, MI)        

We have a Bosch Ascenta dishwasher, model not easily obtainable (it's on the side of the door facing a cabinet) anyway it's a couple years old and recently it hasn't been cleaning and/or rinsing well. It's had pretty heavy daily use but still seems to sound/act normal, water is being heated, cycles take normal amounts of time etc.. If I open the door quickly water is spraying from both arms and they seem to be turning. Normal everyday food soil is being removed but the majority of that is deposited in the filter at the end of the cycle, and any water remaining in the sump is cloudy and starts to smell after about 24 hours. Dishes look cloudy and streaked, anything dark has a film on it.. Dishes don't "feel" clean. We have been using Sam's club ultimate clean pods since we got the dishwasher new, and recently bought a box of Cascade complete powder when things weren't getting clean.. That works in very small doses- small enough I'm not sure it's doing any good.. Like a teaspoon or so or else everything is streaked. Using Jet dry in the dispenser, believe it's at setting 2 of 5. Filter used to go months between cleaning, now it's partially blocked every few days if I don't clean it. I usually use the Heavy Wash or Auto Wash with or without sanitize. Something's up and I'm not sure what, but I don't like it. Any advice is appreciated but I have checked everything obvious and to the best of my ability, just running out of ideas and not wanting to replace it if I don't have to.

Post# 1046857 , Reply# 1   10/4/2019 at 23:27 (276 days old) by combo52 (Beltsville,Md)        
Poor Cleaning Bosch DW

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We see a lot of these that have bad inlet valves, often as they fail they do not let enough water in the DW.


To test try adding about 1/2 gallon of hot water after the DW has filled and is running, if the wash action improves noticeably change the inlet valve.


John L.

Post# 1046869 , Reply# 2   10/5/2019 at 01:39 (275 days old) by MattL (Flushing, MI)        

One other thought might be a partially block drain line.  If the sump water starts to smell after 24 hours odds are garbage is collecting there and not getting pumped out.

Post# 1046871 , Reply# 3   10/5/2019 at 03:43 (275 days old) by thomasortega (El Pueblo de Nuestra Señora de Los Angeles de Porciúncula)        

A third possibility is the detergent.

Try Cascade Fryer Boil out. You can find it on Amazon.

This product, now meant to be used to clean deep fryers in restaurants is nothing more, nothing less than the vintage Cascade dishwasher detergent.

You'll be shocked with the results after the second or third load. The first and second loads it will actually clean your dishwasher and get rid of that nasty film left by regular modern dishwasher detergents.

Post# 1046879 , Reply# 4   10/5/2019 at 07:14 (275 days old) by DADoES (TX, U.S. of A.)        

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Boil Out (formerly Cascade Institutional) has been my go-to for 8+ years, is a phosphates/chlorine bleach formula.  It works great for tea/coffee/tomato stains on plastics and majority of soil types ... but not on egg residue (which needs enzymes).

Post# 1046909 , Reply# 5   10/5/2019 at 15:54 (275 days old) by jamiel (Detroit, Michigan)        

Presumably you've taken out the bottom wash arm and made sure the downward-facing sweeper nozzle (sweeps debris off the metal screen into the fine filter) isn't clogged (so is actually washing debris into the cylindrical fine filter). Other than that I've got nothing...our Ascenta does a fine job.

Post# 1046917 , Reply# 6   10/5/2019 at 17:37 (275 days old) by henene4 (Germany)        

Dunno about US machines, but EU machines of last gen (before the EcoSilenceDrive was introduced) could get clogged float\pressure switches and\or airgaps in the water pocket which led to further and further lowering of fill levels...

What's the age of the machine?

Post# 1046986 , Reply# 7   10/6/2019 at 16:57 (274 days old) by petek (Ontari ari ari O )        

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Can't add anymore suggestions than what others have.. I'm perplexed though when you say it's a model not easily obtainable positioned on the side of a door facing a cabinet? side of a door?

Post# 1046996 , Reply# 8   10/6/2019 at 17:37 (274 days old) by earthling177 (Boston, MA)        


A bunch of Euro Dishwashers have a sticker containing the appliance info (Model Number, Serial Number, Voltage, Wattage etc) that is located either at the left or the right side of the door, so, when you open the door, you can look at it.

Trouble is, when a kitchen layout is an L, it can easily happen that the dishwasher door can open just fine, but you cannot look at that label because it is facing another cabinet and there's not enough room for a person to look at it or photograph it.

(The Dishwasher in the picture [which I found by googling] would make it very hard to see the label if it were on the right side of the door, for example.)

CLICK HERE TO GO TO earthling177's LINK

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Post# 1047038 , Reply# 9   10/6/2019 at 21:37 (274 days old) by Dustin92 (Jackson, MI)        

I used the Cascade institutional formula once years ago and it didn't do well with our hard water, plus if I remember properly, Bosch doesn't want detergents with chlorine used in it.. I do cheat and add a splash of bleach when it starts to smell funky.
Yes that picture is similar to the setup we have, our sink is to the right and the dishwasher opens in front of it.. The kitchen is a small U shape more or less. Weird setup I know, but it works. Both wash arms are completely clean and turn freely. It's still washing dishes but not as well before and there is usually food residue left in the filter or on the bottom of the dishwasher, whereas that was being washed away before. Dishes seem to have a food or detergent residue, which can be seen in the picture to follow.

Post# 1047039 , Reply# 10   10/6/2019 at 21:42 (274 days old) by Dustin92 (Jackson, MI)        

First pic is filter after one load, it normally doesn't get this dirty in a month.. Second pic shows residue on the black air fryer basket- I wiped some away to show the difference. This was after a normal/lightly soiled load washed on heavy wash with sanitize.

  Photos...       <              >      Photo 1 of 2         View Full Size
Post# 1047041 , Reply# 11   10/6/2019 at 22:53 (274 days old) by appnut (TX)        

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Have you tried the suggestion above to add more water after it fills for a cycle circulation phase and see if that improves the situation? That's implying that it's not it's getting as much water is it used to in should be for Effective cleaning. This a restricted inlet valve

Post# 1047048 , Reply# 12   10/7/2019 at 06:00 (273 days old) by appnut (TX)        

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Dustin, you mentioned hard water.  Hard water killed the distribution valve in my Kenmore Elite (KitchenAid) 2 years ago.  4 loads later, hard water also contributed to the failure of my pump overall.  It was noted on the invoice evidence of hard water build-up was noticed with the first repair.  The repairman, who had been repairing for over 30 years, suggested I I use Lemi Shine dishwasher cleaner once a month and also put some Lemi Shine dish detergent booster in the dispenser with the tablet/pod.  I also put a little Cascade Complete powder in the prewash dispenser each load too.  Thus far, no issues 2 years later.   the next time I replace the dishwasher, I'm going to get a model with built-in water softner.  

Post# 1047312 , Reply# 13   10/9/2019 at 19:55 (271 days old) by SudsMaster (East of SF, West of Eden, California)        

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I recently had an issue with an older Bosch (SHU43C) that's about 15-20 years old. The problem was not with the water inlet valve, but with the drain valve. It wasn't draining completely and yes, there were would be dirty water at the end of the cycle - to the point where it was above the coarse filter. Replacing it wasn't difficult and fixed the problem. It went back to washing as good as new. A subsequent problem was a lot of noise when draining. Apparently something got past the fine filter (I found a plastic blood glucose test strip in the sump). I pulled the cover over the drain pump and sucked out what water and debris that was in there (with a little wet vac, of course). It's possible there was some broken glass in there as well. Again, it's back to normal after that.


One thing I've noticed is that with this Euro style dishwasher, with no disposer function, it's important to keep food debris off the stuff being washed. The fine filter does a good job keeping debris out of the recirculation, but then it seems to try to flush it down the drain, past the fine filter. Sometimes that debris gets hung up in the air gap on top of the sink.  It's possible your drain line is blocked, as somebody already suggested.


Post# 1047331 , Reply# 14   10/9/2019 at 23:43 (271 days old) by askolover (South of Nash Vegas, TN)        

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Can you stick a camera inside and film a cycle? 

Post# 1048472 , Reply# 15   10/22/2019 at 21:09 (258 days old) by Dustin92 (Jackson, MI)        

Well life has happened and I haven't posted on here in a minute- we do use the LemiShime booster and I did find a small amount of stuff in around the drain pump port- cleaned it out but doesn't seem to have a lot of effect. It is draining completely but the small amount of water left under the filter in the sump is cloudy and greasy. I did add a quart of water to a cycle once it had started washing and it just drained it back out and continued washing. I did notice a different noise as the cycle is starting before the pump ramps all the way up, sort of a vibration.. It seems like when it's making that noise the pump is losing speed, I'm wondering if unfortunately the pump is starting to fail. Hopefully it's something simple, if we end up replacing a 2 year old high end dishwasher, it won't be another Bosch.

Post# 1048687 , Reply# 16   10/24/2019 at 18:05 (256 days old) by SudsMaster (East of SF, West of Eden, California)        

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When my Bosch failed, I had been using some Costco dishwasher detergent packs. I didn't like the results - cloudy water, deposits, and streaking. I switched (back) to Finish Tabs and the results are much better. Of course the  problems with the Costco detergent might have been related to the other problems the DW was having. I haven't gone back to it so see. Although I have a large amount left.




Post# 1052326 , Reply# 17   11/25/2019 at 23:37 (224 days old) by Joe_in_philly (Philadelphia, PA, USA)        
Slow sink drain?

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I had something sort of similar happen with my Bosch dishwasher.

When the drain in my kitchen sink was partially clogged and draining slowly, I had grit on the “clean” dishes. In my case everything looked clean, but I could feel some grit on the dishes and the water in the sump at the end of the cycle looks cloudy. I would run the dishwasher at night, and didn’t know what was going on at first. But I realized that when the dishwasher drained (into the garbage disposal) it would back up into the disposal and even a little into the sink. When the drain pump stopped, some of the dirty water would drain back into the dishwasher. Once the drain was cleared the problem went away.

I believe one plus of the Bosch’s heated wash and final rinse is that it seems to keep my kitchen sink drain clear. Before I got the Bosch dishwasher my kitchen drain would get slow a few times a year. In the 14 years I’ve had my Bosch dishwasher the sink drain has only become slow that one time.

Post# 1052425 , Reply# 18   11/27/2019 at 02:21 (222 days old) by SudsMaster (East of SF, West of Eden, California)        

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I confess I'm getting a bit tired of having the clear the air gap on the sink before each time I run the dishwasher.


Last time I had the Bosch out from under the counter, I noticed that the drain line takes a big loop up to the top of the dishwasher. I am thinking this effectively functions as an anti-drainback feature - at least that's the impression I got from the manual. I am thinking of reconnecting the Bosch direct to the disposer port, and bypassing the air gap nonsense. Anybody else try this?


I suppose the worst that can happen is dirty drain water being flushed back into the dishwasher. The benefit could be not having to clear the air gap all the time.


Post# 1052430 , Reply# 19   11/27/2019 at 05:31 (222 days old) by Logixx (Germany)        

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Sometimes I wonder if these kitchen sink air gaps even exist outside of the US... Have never had water backing up into any brand of (Euro) dishwasher.

Post# 1052432 , Reply# 20   11/27/2019 at 05:47 (222 days old) by ozzie908 (Lincoln UK)        
Similar problem

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My Miele dishwasher drains into the waste disposer it does remove grease etc but a bad design in the plumbing under my sink is, there is no way to clean out the pipe that goes to the main drain, We have to remove all the pipes and use a pressure pump to unblock it now the problem I have had is the water pumped from the DW never goes back into it as it has a anti syphon which believe it or not is just a large stainless steel ball sat in a housing that drops when the pump stops thus preventing back flow. A simple but effective device I wish the plumbers and electricians had thought about my sink though as we have a boiling water tap with a trap that allows unused water to drain away if we have a blockage every thing flows out of this little trap and guess what's been fitted directly under it ????? Yes the power points for the DW etc so off goes the power so not only is it wet its now dark.... All good fun lol

Post# 1052436 , Reply# 21   11/27/2019 at 07:29 (222 days old) by combo52 (Beltsville,Md)        
Built-In DW Air-Gaps and other Anti-Siphon Devices

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Most built-in DWs in the US originally required a drain air gap , a drain AG is the ONLY way to completely insure that dirty can-not possibility back up into your DW that is always installed lower than the sink and sinks drain line.


Many parts of the US did not require AGs so DW manufactures started building various types of built-in check valves into the DWs plumbing, these helped a lot, but if a tiny bit of glass or other object gets in the CV it will not function.


Having a high loop also helps a lot but of course dirty water can still siphon back through a HL.


Because of these improvements in DW design most places in the US have stopped requiring sink mounted AGs, here in the Washington area we no longer have to install them. We just loop the drain line as high as possible under the sink and secure it to the under side of the countertop and hope for the best. This type of installation would not pass muster in commercial installations etc however.


Hi Rich, in your case you can probably just get rid of the air gap or replace your AG, an AG should almost never clog so there is truly something wrong with your current AG if you are having to clean it on a regular basis, we still have thousand of customers with AGs and they generally do not even know they have one let alone know how to clean it.


John L.

Post# 1052445 , Reply# 22   11/27/2019 at 09:57 (222 days old) by foraloysius (Leeuwarden, Friesland, the Netherlands)        

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No air gap here either, never seen one in the NL. My dishwasher is connected to the sink drain.

Post# 1052446 , Reply# 23   11/27/2019 at 10:01 (222 days old) by foraloysius (Leeuwarden, Friesland, the Netherlands)        

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I found an installation instruction for my dishwasher online. No air gap required.

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Post# 1052469 , Reply# 24   11/27/2019 at 14:29 (222 days old) by marky_mark (From Liverpool. Now in Sitges [Barcelona] & Palm Springs, CA)        

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My dishwasher in Spain is connected directly to the Insinkerator disposal -- all that hot water and detergent running through it keeps my disposer and drains as clean as a whistle.  No air gap, but it does have a check valve of course, which functions as Ozzie describes in his post above.  I have never seen dishwasher air gaps outside of the US.  


The most useful thing about having a sink with an air gap is that you have the option (local code permitting wink) of removing it and using the hole for something else such as a soap dispenser, air switch, sprayer, reverse osmosis, boiling water unit etc.


I can't offer any advice to the OP that hasn't already been mentioned.  I hope you get the problem resolved!

Post# 1052515 , Reply# 25   11/27/2019 at 22:10 (222 days old) by SudsMaster (East of SF, West of Eden, California)        

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Thanks for all the responses. This DW is a Bosch SHU43-C/U. I'm not sure if it has a check valve, but I suspect it does.


The air gap is very old - made of copper mostly. The problem is that relatively small pieces of food, maybe 1/2" long and 1/4" wide at most, get caught at the top of the air gap before the path goes 180 degrees down again. There simply is not enough clearance between the copper feed pipe into the air gap and the plastic cap that covers it - too tightly it would seem. I have tried cutting away part of the air gap to make more clearance, but this doesn't eliminate the problem.


I will probably try by-passing the air gap  and monitor the DW sump to make sure it doesn't flood from the sink. I doubt it will. I figure the SHU series is new enough that it has built-in anti-drainback features as mentioned.


I will however keep the current airgap in place, but not connected to anything, since I have a few vintage American style DW's in storage, one of which might wind up in place of the Bosch should it ever finally die for good.


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