Thread Number: 84941  /  Tag: Modern Dishwashers
Dishwasher Pre Wash
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Post# 1094077   10/22/2020 at 17:20 (1,252 days old) by chetlaham (United States)        

chetlaham's profile picture
So yesterday I opened my Maytag during the pre-wash and their was a stream of "soapy" water running out and down the detergent dispenser. Which got me thinking. How essential are pre-washes?

A lot of older machines had 3 or more prewashes and typically two rinses. GE had 3 rinses, Whirlpool often had one rinse with a post main-wash purge.


Later machines seem to be ditching pre-washes and adding more rinses. I remember the 2002-2006 Maytag tall tubs had one or two pre-washes, but added 5 or more rinses depending on the soil level according to the tech sheet. My maytag at most has done only one pre-wash, but I've noticed 4 or more rinses on average. Tech sheets of newer machines (excluding Frigidaire) indicate the same- less prewashing more rinsing.


For those who don't know my terminology goes like this:

Prewash- any fill and drain BEFORE the main wash

Mainwash- the cycle where the detergent cup opens.

Rinse- and fill and drain AFTER the mainwash.

I know people think of rinses as anything without detergent (a prewash could be called a rinse) but thats not what I have in mind.

With that said, can dishwashers even successfully skip the pre-wash altogether and just tag along 4-6 rinses?





Post# 1094091 , Reply# 1   10/22/2020 at 20:14 (1,252 days old) by murando531 (Augusta, Georgia - US)        

murando531's profile picture
I use the exact same terminology when talking DW cycles. A Prewash is always the quick washes before the main wash, because to me calling it a "prerinse" doesn't click right seeing as how the water is going to be dirty and possibly have detergent as well. Then comes the Main Wash, then how ever many rinses, then the Final Rinse. The terms Purge and Eco Rinse come up too sometimes when talking with fellow washer fanatics because of newer machines being designed with clever ways to flush the filters clean without a full fill charge.

Purge, for example with Whirlpool machines, is like what the PowerCleans do after the main wash on the Normal cycles, filling with enough water to surge through the filter assembly and arms for a second or so before draining. The Voyagers and GlobalWash machines also do this before the main wash on certain cycles and sensor readings. The GWs I've had have been known to do two of them back to back after the main, and very often in between the prewashes as well.

Eco Rinse is still a "purge" but with slightly more water. The GlobalWash platform is the first I've known in WP's designs to do this, but it involves filling with about half the normal fill charge, and running the pump for a few seconds at a time, which causes just enough of a surge of water through each arm or arms to spray for a second or two at high pressure and rotate slightly before surging on air, pausing for about 15-20 seconds inbetween, and it does this repeatedly for several minutes, so that by the time it drains, the whole load has been sprayed down at least once from top to bottom. Then follows either another full rinse or final rinse.

Interestingly, the new house we moved into a few months ago had a 2006 PowerClean installed, which I tried for a day or two before replacing it** with my TOL 2004 PC. This slightly newer model isn't changed at all except that the Heavy cycle defaults to a prewash, 135F main wash, but then in place of the normal purge, it actually does something more like the "Eco Purge" where it fills with a bit more water and runs the pump for a minute, with the water surging and cavitating just enough to spray a bit at a time through the arms. It's the first PowerClean I've ever come across to do this, and only on Heavy. The Normal cycle would still use the traditional purge behavior. (**The existing one just hadn't been taken care of and because I have two immaculate machines already, it doesn't make sense to invest time in restoring a third one so my plan is to part it out.)


Post# 1094098 , Reply# 2   10/22/2020 at 20:51 (1,252 days old) by murando531 (Augusta, Georgia - US)        

murando531's profile picture
Moving on to the subject of prewashes being necessary, I'm probably about to blaspheme in everyone's eyes because prewashes to me are overkill in 99% of dish loads. Drag me through the dirt I guess, but the idea of filling a dishwasher full of dirty dishes, then setting it to its roughest longest hottest cycles just takes the fun out of how the machine works, *especially* on older dishwashers like the PowerCleans and old school KitchenAids. It's interesting that we all agree that manually rinsing dishes clean before loading them is just wasteful and silly, and yet running a Pots&Pans cycle with two full detergent cups full practically does just that, because after those 2-3 prewashes, (in most cases HEATED prewashes) those dishes are spotless before the main wash even starts. As a result, that main cup of detergent is popped open to barely any food residues at all, which seems to me to cause the same problem as people who scrub everything clean before loading and then complain that their racks are corroding away or the motor seal has etched away and caused water to ruin their nice floors.

Prewashes in a cycle seem even more unnecessary when considering that modern detergents actually perform best with food soils to activate them. I've washed more loads than I can count that were filled with dishes covered in sauces and dried goop and the door and tub bottom completely covered in drips and splatters, and after just a Normal cycle in the PowerClean it's all spotless, and that's with going straight into the main wash AND a purge before the final rinse! *gasp*

One thing I will add to be fair is that with the shorter wash cycles of the PowerClean and older machines, because I know for sure it's going to start with the main wash, I'll drop the detergent pac in the bottom of the tub and just close the cup to get that satisfying pop when opening the machine when it's done. That way the pac is already dissolved or almost dissolved during the fill before the wash action starts. Otherwise the detergent actually doesn't dispense until 6 minutes in, and the whole main wash is 12 min, which worked fine in the days of phosphate Cascade powder, but I like knowing my Platinum pacs today are getting the full time. Since doing that, I've never had anything after a Normal wash in terms of specks leftover or residues or odors.

This all is not to say that one prewash isn't sometimes useful in a super heavily soiled load, but I think one is plenty. That's all the PowerClean will do when set to Normal with Hi Temp Wash selected, and it's just a six minute prewash to sweep away the loose excess but not enough to take away all the soil before the main. I never actually use the Heavy on my machines and haven't even touched Pots&Pans because they both have thermal hold prewashes, and that's just... too much energy and water for no reason.


Post# 1094103 , Reply# 3   10/22/2020 at 21:11 (1,252 days old) by iheartmaytag (Wichita, Kansas)        
In my head

iheartmaytag's profile picture
And probably no one else's, I have viewed the pre wash as purge wash of sorts. It helps to start loosening the soil that is more easily washed away, as well as it serves to start heating up the tub and dishes so the main wash will be hotter and detergent more effective.

This may be able entirely wrong, but I justified it that way when I used to lay in front of the Mobil maid and listen to the wash action.


Post# 1094107 , Reply# 4   10/22/2020 at 21:31 (1,252 days old) by RP2813 (Sannazay)        

rp2813's profile picture

I think Andrew has made valid points about machines pre-washing vs. pre-rinsing by hand.  I never use the pre-wash cup in my Miele.  It's not necessary.

 

Disclaimer:  Since it's just me in the house most of the time, I use the rinse/hold option as needed.  Usually this happens when there's soil on the dishes such as egg residue that could dry and harden.  Without fail, after I run the rinse/hold, the dishes look sparkling clean.  This after just a few minutes of run time with water that the machine hasn't even heated.

 

When adding the last items that will fill the machine and call for a full cycle, I scrape but don't pre-rinse so there's soil for the detergent to work on, I run a "normal" cycle and only use the main wash detergent dispenser.  Never a pre-wash no matter how much soil, such as a BobLoad after hosting a dinner party.  Without fail, contents come out sparkling clean. 

 

As far as modern day well-designed dishwashers are concerned, there is no need for a pre-wash IMO.


Post# 1094109 , Reply# 5   10/22/2020 at 21:36 (1,252 days old) by chetlaham (United States)        

chetlaham's profile picture
I agree, never pre-rinse.


And yes, per washes warm up the machine.


All good replies, keep em coming!


Post# 1094111 , Reply# 6   10/22/2020 at 21:58 (1,252 days old) by GELaundry4ever (Nacogdoches, TX, USA)        
My kenmore

will do a pre-wash, main wash, first rinse, final rinse then heat dry on the cycle I use all the time. Mine is great about making sure all the detergent is rinsed off and rinse aid evenly distributed through.

Post# 1094158 , Reply# 7   10/23/2020 at 08:51 (1,252 days old) by chetlaham (United States)        

chetlaham's profile picture
You have good tastes in appliances GELaundry4ever. :)

Post# 1094161 , Reply# 8   10/23/2020 at 09:07 (1,252 days old) by henene4 (Heidenheim a.d. Brenz (Germany))        

I think pre-rinse is coming from our side of the pond.

When DWs were new our washers often as a standard still ran a pre-wash with detergent.
So for us, everything with detergent is a wash, everything without a rinse.

Thus pre-rinse.


Anyway...




Over here a lot has changed since DW filters became actually really fine and thus cought a lot of dirt quite well.

Most up-to-date design from what I see are ultra fine wavey filters.
That waveyness adds a lot more surface area and thus more filtering ability before needing back-washing.



Most eco cycles here don't do a full pre-wash anymore.

Either they don't at all or they do a cheat pre-wash (actually the latter is far more common, especially with variable speed pumps).

They cheat by filling with a larger (or rather normal), often sensor based amount of water and run a pre-wash at normal pressure.
Then, depending on conditions, they run the drain pump for a calculated amount of time (2-10sec, depending, from my experiece) and without refillign start the low rpm main wash.

Less water means higher detergent concentration and less energy to heat up.





But Auto-cycles have become verry accurate as well.

Our Bosch in the old flat tended to run a full pre-wash, medium or low stregth main wash, full rinse and final rinse.
Never did it run its theoretical full load version.

Our slimline Bosch back home tends to not run a prewash, therefor a more intensive main wash.



My Miele here is all over the place.

That is the first EU machine that I know that does the eco-rinses (always on Eco, sometimes on Auto) and whose energy usage is quite variable (first I can actually observe due to eco feedback).
Part of that is the sensor drying, part of that is "guided energy usage", part if that is on point load sensing.

The Auto cycle supposedly goes from 6l to 13l and 0,6kWh to 1,2kWh IIRC.


I've seen it peak at 14l and 1,4kWh - it has an option that allows the machine to calculate when it would be beneficial to run a hotter final rinse plus higher water levels if temperatures have been to low during to many cycles.

Basicly automatic maintenance included in a normal wash.

Worst case would be slightly higher actually if the water softner regeneration, hygiene rinse and high soil load would coincide.


Lowest I have seen was 8l and 0,7kWh on a low soil run.

But I have seen low water usage with up to 1.1kWh as well and high water usage with lower energy usage as well.


Post# 1094176 , Reply# 9   10/23/2020 at 11:29 (1,252 days old) by GELaundry4ever (Nacogdoches, TX, USA)        
To chetlaham

I appreciate it.

Post# 1094200 , Reply# 10   10/23/2020 at 14:28 (1,252 days old) by lakewebsterkid (Dayton, Ohio)        
Pre-Wash

I had a nice long post, but it did not post.
However, I use the Auto cycle on my Bosch specifically for the pre-wash.
But, in a machine that has a food chopper it isn't as necessary.


Post# 1094386 , Reply# 11   10/24/2020 at 17:17 (1,250 days old) by Jerrod_Six (Eastern Pennsylvania, USA)        
USA Miele DW

I have a Miele 6987 and for the Normal cycle, the majority of the time the prewash water is used for the main wash also. According to the app on my phone, it takes about 1 gallon and uses that for the Prewash and the main wash. The first rinse uses .7 gals, and the last uses .8 gals. I wash 2-day old dishes that have been sitting unrinsed and the Normal cycle cleans them well.

On the Normal cycle, the prewash always lasts 18 minutes and the main wash is usually 36 min. I measured the water temperature of the wash once and it was 132F. Whenever it does change the water for the wash, it results in a wash of about 60 minutes, but this rarely happens.

Pots and Pans use 1 10-minute prewash, followed by a water change, a wash, and low water level rinses.

So it seems like for this dishwasher a Prewash with a water change is not important unless the soil level is high.


Post# 1094625 , Reply# 12   10/26/2020 at 09:37 (1,249 days old) by lakewebsterkid (Dayton, Ohio)        
Prewash

So, our old Point Voyager would occasionally skip the pre-wash drain and go straight into the main wash using the same water. It could perform an AFP and remove some of the junk from the sump before starting the wash.
With that being said, I would much rather have purchased a Global Wash machine that would have performed 1 pre-wash, main-wash, and 2 deep rinses. But I did not have control over that. Lol.
I will say, that our Bosch will perform 3 pre-washes on the Heavy cycle when a high soil level is detected. The third pre-wash is actually heated and removes a lot of crap.


Post# 1094684 , Reply# 13   10/26/2020 at 16:19 (1,248 days old) by Jerrod_Six (Eastern Pennsylvania, USA)        
lakewebsterkid

What model Bosch do you have and when was it purchased?

Post# 1094972 , Reply# 14   10/28/2020 at 18:26 (1,246 days old) by IIIJohnnyMacIII (North Carolina)        

iiijohnnymaciii's profile picture
I believe that a prewash is important. Particularly a quick unheated one.

I’ve noticed that machines that start with a quick prewash do a great job of keeping Tupperware from getting stained with red sauces.

The quick prewash does just enough to get most of the red sauce out of the dishwasher so that when the main wash happens, the wash water isn’t saturated with red sauce and plastics are much less likely to get stained.


Post# 1094982 , Reply# 15   10/28/2020 at 19:31 (1,246 days old) by Cam2s (Nebraska)        

I probably tend to use a more aggressive cycle than what I need but I always like a prewash. My Bosch if you used normal could decide to skip the prewash or not, it usually would always add one in. I usually used power scrub which forced a heated prewash, sometimes with really mucky loads it would add in another. My old school Potscrubber that I’m using now uses 3 prewashes on Power Scrub and Normal/Heavy soil and 2 if you use normal/regular soil or China. Even though mine has the passive filtration system the extra fills are suppose to help flush soil out and also warm the interior, since it has a weak heater and calls for 140 degree water. One of these days I’m going to test the effectiveness of the filtration system and run a cycle where I skip the extra fills and run a WWRR program.

Post# 1095100 , Reply# 16   10/29/2020 at 17:40 (1,245 days old) by lakewebsterkid (Dayton, Ohio)        
Dishwasher

SHE863WF5N Jerrod_Six
I purchased it in February of 2018. I thought it was actually older.

IIIJohnnyMacIII, I agree with your statement!!


Post# 1095771 , Reply# 17   11/4/2020 at 11:32 (1,240 days old) by IIIJohnnyMacIII (North Carolina)        

iiijohnnymaciii's profile picture
Yeah, that’s the problem I have with my power clean. The prewash cycle is more than 15 minutes long and stains my interior and plastics. It doesn’t matter if I fill the entire prewash cup with bleach based detergent or not. I wish there was a quick 3-4 minute prewash like my old kitchen aid had. Nothing ever stained.

Post# 1095796 , Reply# 18   11/4/2020 at 13:55 (1,240 days old) by murando531 (Augusta, Georgia - US)        
15 minute PowerClean prewash

murando531's profile picture
On what cycle? The only cycles that have any sort of long prewash on the latest year PowerCleans (since 2002-2009) are the Pots and Pans/Antibacterial cycles, depending on the model. The Heavy cycle has just a quick prewash before the heated main wash. Normal goes straight into main wash, which when paired with dropping a detergent pac into the bottom of the tub and not going crazy with adding extra to the cups, does perfectly for anything except scorched/baked on soils. The Normal cycle on its own always heats the water for the 12 minute duration, and dropping the pac in allows the fill to dissolve it before the wash action ever starts so you get the full time with detergent and enzyme cleaning.

Adding Hi Temp to a Normal wash will give you a similar 6 min non-heated prewash, then a 135F temp hold main wash, which is the most I've ever had to use for a PC, and it's mainly for super heavily soiled loads with dried on foods that have sat for a day or two. The Pots and Pans cycle, and adding Hi Temp to anything other than Normal, is just overkill and guzzles extra water, because the dishes will be clean before the detergent cup ever opens and at that point it's just eating away at the rack coatings and seals.



Post# 1095804 , Reply# 19   11/4/2020 at 15:02 (1,239 days old) by IIIJohnnyMacIII (North Carolina)        
Thanks!

iiijohnnymaciii's profile picture
I appreciate it very much. I have been using the pots and pans cycle this entire time. I will try the Normal cycle with a heated wash. I thought for the life of me when I ran the heavy cycle it was a long prewash, but I wasn’t exactly timing it and left the kitchen a couple of times and it probably switched over when I was out. I didn’t even know that I could get a prewash out of the normal cycle. Thanks again for the advice!

Post# 1095847 , Reply# 20   11/4/2020 at 19:12 (1,239 days old) by IIIJohnnyMacIII (North Carolina)        
4 min Prewash!

iiijohnnymaciii's profile picture
I set it to normal and hi-temp and it did indeed have a 4 min prewash, 18 min main wash, 8 min rinse, and a 15 minute final rinse. That is absolutely enough to clean anything I can throw at it and no more stains!

Post# 1095848 , Reply# 21   11/4/2020 at 19:15 (1,239 days old) by Rolls_rapide (.)        
Auto sensor programmes

The first generation of these were pretty hit and miss. My Bosch which always did a prerinse, recently decided not to do so on its 'auto normal' cycle. It also has a nasty habit of washing in lukewarm temperatures. Drying can be a tad spotty, leaving watermarks on cutlery. Not impressed.

I once ran a bottle of dishwasher cleaner through on this programme... the wash water was far too cool to melt the wax cap!

To get sensible temperatures, you have to select the 'Auto Super Wash' programme. Which I generally do, most of the time. Better drying too.


Post# 1095874 , Reply# 22   11/4/2020 at 21:55 (1,239 days old) by chetlaham (United States)        

chetlaham's profile picture
Didn't they make a DW without a prewash once? And it had no door over the cup? Can someone post pics of these machines?

Post# 1095883 , Reply# 23   11/4/2020 at 22:54 (1,239 days old) by murando531 (Augusta, Georgia - US)        

murando531's profile picture
I’m not sure I’ve seen a full-size machine with no dispenser cup but I do think I remember the KitchenAid Briva In Sink dishwasher that had a sort of scoop on the lid that you measured detergent into, and when the lid closed down it would just dump down into the tank. I would love one of them just to try out.

@JohnnyMac No problem! The PowerCleans are a breed of dishwasher that really performed and still perform better with less. My aunt still has her original 2002 model from when their house was built, which is similar to mine but with the five cycle buttons. That thing is still going strong with a family of five, previously 7, living in the same house, with strictly Normal cycles on Air Dry being fully packed to the brim and they just scrape and never rinse. Sometimes there will be bits of food in the tub bottom and everything has always come out perfectly. Her machine still somehow is immaculate inside.

I’m not surprised about the staining if you were using PnP, because that’s a thermal hold prewash at 135 as well as thermal hold for the main wash. The soiled water was practically being boiled in lol


Post# 1096149 , Reply# 24   11/6/2020 at 23:01 (1,237 days old) by combo52 (50 Year Repair Tech Beltsville,Md)        
DWsWith No Covered Detergent Cups

combo52's profile picture

There were many DWs without a detergent dispenser, mostly older earlier models, [ like Kitchenaid KD-10 ]

 

I think one of the latest machines were the basic WH DWs from the early 70s.

 

Manufactures quickly found DWs perform much better with either a pre-wash or at least a pre-rinse, I always use the double wash in our 1987 WP PC machines unless I am just washing dusty dishes that were in storage etc.

 

John L.


Post# 1096156 , Reply# 25   11/7/2020 at 00:41 (1,237 days old) by Marky_mark (From Liverpool. Now living in Palm Springs and Dublin)        
Red Stains

marky_mark's profile picture

If you want to remove the red/orange stains from plastic items (such as cutting boards and plastic containers) and from plastic dishwasher tubs, typically caused by tomato, you used to be able to buy Cascade Plastic Booster which is now no longer available.  Fortunately its active ingredient, benzoyl peroxide, is widely available, sold as acne cream.  

 

You add 1 or 2 tablespoons to the prewash and add regular detergent for the main wash.  It works very well and is especially good if you can select a cycle with a longer prewash, such as “pots and pans” on the Whirlpool PowerClean.  Regular detergent and chlorine bleach will not remove the stains. 

 

Here is a photo I have just taken of a plastic tube that has gone red.  I will wash this over the next few days and will add some benzoyl peroxide to the prewash.  I’ll post the “after” photo.  I don’t currently have any other plastic items with orange/red stains as I’ve already recently washed them with benzoyl peroxide added to the prewash. 

See my previous thread:



CLICK HERE TO GO TO Marky_mark's LINK

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Post# 1097503 , Reply# 26   11/18/2020 at 09:55 (1,226 days old) by IIIJohnnyMacIII (North Carolina)        
Update

iiijohnnymaciii's profile picture
So, after about one week of use on Normal with a heated wash selected, I have zero stains! Yesterday was Spaghetti night and everything came out immaculate, including the tub! I basically use the 4 minute prewash as a prerinse. I only use one Cascade Platinum tab in the main wash with no rinse agent or prewash detergent. Once again thank you Andrew for the insight! Less time on the wash and saves me money with detergent as well!

Post# 1097506 , Reply# 27   11/18/2020 at 10:07 (1,226 days old) by lakewebsterkid (Dayton, Ohio)        
PowerClean

My aunt also has her Kenmore UltraWash from around 1998-2000. It was ran almost every day for about 18 years. She always uses Normal, Hi Temp, Sanitize, Air Dry. Zero issues. She does use a bleach based gel that has made the stainless look a little rough, but she really doesn't have any rusting racks either. Kind of shocking. I was always impressed with how quiet that machine was.

Post# 1097507 , Reply# 28   11/18/2020 at 10:10 (1,226 days old) by lakewebsterkid (Dayton, Ohio)        
Dishwasher 'rinsing'

My mom's fiance has a rental house with a Samsung DW7933. The machine does a piss poor job of cleaning. I actually took the sump apart and tried to clean the entire thing apart to see if that helped. When using the Heavy cycle, I did notice that the machine will do a very prolonged fill and drain simultaneously (~1 minute). So I guess excessive pre-rinses can occur too! Lol.

Post# 1097508 , Reply# 29   11/18/2020 at 10:12 (1,226 days old) by lakewebsterkid (Dayton, Ohio)        
Benzoyl Peroxide

I have used it with great success when using it in the detergent dispenser. I try to add a little whenever there is quite a bit of tupperware in the machine, especially on trash night. Not much else seems to do the trick.

Post# 1097509 , Reply# 30   11/18/2020 at 10:16 (1,226 days old) by GELaundry4ever (Nacogdoches, TX, USA)        
I wish

they would bring Cascade plastic booster back.

Post# 1193320 , Reply# 31   11/10/2023 at 10:22 by GELaundry4ever (Nacogdoches, TX, USA)        
pre-rinsing

I completely agree with Murando531 on this one. Some people are just too stupid to be doing dishes. It drives me insane when people do that. I put filthy dishes in my Kenmore (Bosch) dishwasher and the racks are still intact. Why? Because I don't pre-wash anything. I just put them directly in after scraping.


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