Why do some dishwashers run the wash pump while the drain pump is running? I never understood the reason for this.
Wash pump running while draining
- Thread starter Chetlaham
- Start date
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grease....
You're on to something- tell me more! 
backflush....
Even for a manual filter model?
Yep...
A tricke of water helps pushing the oil film to the drain.
A tricke of water helps pushing the oil film to the drain.
the GE
potscrubber dishwashers did this too, even when filling.
potscrubber dishwashers did this too, even when filling.
vacerator
Well-known member
Yes, my 2011
model year GE Profile does it for about 30 seconds on the pre wash drain.
model year GE Profile does it for about 30 seconds on the pre wash drain.
Noted. If I ever build a DW with a separate drain pump the main pump is staying on for 30 seconds. I'm also probably going to add a purge after the main wash.
How about wash motor running during fill?
Older Whirlpools did the filling when the pump was in wash mode. I like that so that the dishes start to get drenched. I love the sounds of the pump gathering strength.
Older Whirlpools did the filling when the pump was in wash mode. I like that so that the dishes start to get drenched. I love the sounds of the pump gathering strength.
My 2015 Kenmore Elite (aka Kitchenaid product) with the Microclean filter starts draining with 4 short bursts of the drain pump and then the drain pump stays on while the wash circulation pump continues for another 15-20 seconds before the drain pump runs all by itself.
Fill During Wash
Whirlpool machines seem to start half way through the fill. Never understood why but its interesting to hear the pump gather strength.
@appnut- My Maytag is the same. The pump does 2-3 short bursts then stays on. I know why but don't know physics behind it. When you start the drain pump on a full tub of water the amount the comes out of the drain hose is small, but if you pulse the pump its seems to trigger almost a siphon or something because its start to drain like you would expect- fast.
Whirlpool machines seem to start half way through the fill. Never understood why but its interesting to hear the pump gather strength.
@appnut- My Maytag is the same. The pump does 2-3 short bursts then stays on. I know why but don't know physics behind it. When you start the drain pump on a full tub of water the amount the comes out of the drain hose is small, but if you pulse the pump its seems to trigger almost a siphon or something because its start to drain like you would expect- fast.
My dishwasher has a reversing pump motor with separate impellers on the one shaft for wash and drain. The spray arm sits directly atop the upper recirculation impeller. The lower drain impeller is in a small sump.
Current draw on the motor is used to sense the proper fill level so it must run the pump during fill.
It runs the pump on an approx 15- to 20-second cycle (I haven't timed it exactly) for an approx 3-min drain period (I haven't timed it exactly) with momentary little pulses during the dwells.
Sounds both neat and complex. Always been amazed at how complex modern machine sequence/logic has gotten.
Just noticing my current Miele dishwasher, which is from 2017 seems to start the drain pump along side the wash pump.
Perhaps it’s to ensure the filter clears?
European machines use a largely self cleaning filter approach, so the wash pump is sucking water through the sides of the filter, through the fine screens & the drain pump sucks from the bottom with just enough filtration to prevent its impeller being blocked, so most debris will be flushed down the drain.
I was just wondering if perhaps it’s designed to create a bit of turbulence in the filter as the drain pump operates, thus helping to clear the filter mesh mesh screens into the drain pump.
They clear pretty effectively on any machine I’ve had.
Perhaps it’s to ensure the filter clears?
European machines use a largely self cleaning filter approach, so the wash pump is sucking water through the sides of the filter, through the fine screens & the drain pump sucks from the bottom with just enough filtration to prevent its impeller being blocked, so most debris will be flushed down the drain.
I was just wondering if perhaps it’s designed to create a bit of turbulence in the filter as the drain pump operates, thus helping to clear the filter mesh mesh screens into the drain pump.
They clear pretty effectively on any machine I’ve had.
