Many reports say not to prewash for dishwashers to save water. What I have found is I have to prewash in the sink if using ‘quick cycle’ otherwise the items come out not fully clean. However, I don’t have to prewash if using the longer ‘normal cycle’ and they do come out clean. For me it seems that either way I am using the same amount of water? Or not? What do you suggest Choice. Thanks
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Hi @dverted, welcome to the community.
Choice has covered rinsing (‘prewashing’) dishes before putting them in a dishwasher here:
Choice indicates:
"A pre-rinsed plate can ‘trick’ your dishwasher into thinking it’s cleaner than it really is, and the dishwasher will respond by dialling down the power – so your plates could come out dirtier, not cleaner.
which may be why you:
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I share the experience. Light cycles are sometimes for glasses and fragiles, not ‘dirty’ dishes, dishwasher dependent. Other dishwashers might come closer to Choice advice, and probably all will on regular and ‘super’ cycles.
I can only use my ‘light’ cycle for used glasses, bread plates, and others not having much on them. On regular or ‘super’ dirty plates are best. It is a Siemens circa 2011 model.
As often included, Choice advice is a place to start, not an edict in what or how is best for any individual, product, or lifestyle but worth having a go to see how it works for ‘you’.
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Thanks for the replies but the question was more whether I would use more water prewashing before a quick cycle (from which the items do come out clean) or not prewashing and using the normal or longer cycles. I don’t use much water to do a quick rinse. But the dishwasher seems to be using a lot more water on the longer cycles. Does choice know what the water usage is for these two cycles and I can then figure out which way is the best.
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It will depend on:
- how often the dishwasher is run
- how many items are pre-rinsed
- how pre-rinsing is done (running tap or filling up the sink)
Generally, if a dishwasher is only run when full, usually after multiple meals, a dishwasher will use less water on a long cycle than pre-rinsing using a quick cycle. Pre-rinsing can use a lot of water.
While long cycles take longer, dishwasher circulates water in each step of the cycle so for longer cycles, the water potentially for longer. Dishwashers also adjust programs and water use based on the ‘dirtiness’ of the load.
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That should be listed in the specifications for each individual product. From my Siemens, note ‘4’ is water consumption for most cycles, not ‘3’ because water consumption is variable based on the sensors control over some, not all, the cycles.
If you check your owners manual or post make and model perhaps some clarity can be provided? Note the ranges of water consumption; without understanding how the sensors work any conclusion is wobbly at best and subject to specific experimentation and measurement - assuming one could measure the water used in an empiric manner.
Since Choice uses a standard dishwasher load that probably does not reflect common loads in a consumer’s hands, conclusions might best be read as guidance.
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Do you use running water to do your pre-rinse/pre-wash? Is it running with the tap fully open? How long does it take to do in minutes?
This will help determine the amount of water you use to do your rinse. If you partially or fully fill the sink to do the rinse, measure the amount of water you place in the sink.
Roughly a tap allows 5 to 8 litres a minute to flow, most houses now have water saving fittings. Some older houses may not be water efficient and this rate may then be higher. To check flow rate, time how long it takes to fill a 2 or 3 litre or larger vessel or bucket. Divide the amount of water by the time (in minutes e.g., 0.83 minutes or 2.3 minutes or 3 minutes) to get litres per minute the tap allows water to flow at. Time your rinsing, multiply that by the litres per minute and you will have an idea of the amount you use before you put your dishes in the dishwasher.
A pre-rinse in the dishwasher may end up being less use of water than if you pre-rinse under a tap. Or a normal wash may just be as good as a pre-rinse and then a quick wash. For most usage, using a normal wash, is probably going to be more water efficient than rinsing and then washing using a quick wash. Bigger difference will be the energy usage between the different cycles.
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