Need to know
- Dishwashers are more water-efficient than washing up in the sink
- Because most of the energy used to wash your dishes goes to heating the wash water, this means they're more energy-efficient too
- Washing by hand still has its place for many everyday items
These days most of us are pretty conscious of reducing our water consumption, from taking shorter showers and letting the lawn go brown to switching to a water-efficient front loader in the laundry.
But what about in the kitchen? If you think giving up the dishwasher is going to cut down on water use, you might need to think again.
On this page:
- Water use – washing by hand vs dishwashers
- How much water you use washing by hand
- Why do dishwashers use less water than hand washing?
- Is it ever better to hand-wash dishes?
- How to use less water when you don't have a dishwasher
Water use – washing by hand vs dishwashers
A full dishwasher uses about 13 litres of water to clean 144 items.
Washing the same load by hand uses about 100 litres of water on average, according to a study by the University of Bonn in Germany.
It's important to note this is average water consumption – the researchers found actual usage ranged from 33 to a staggering 440 litres!
We'd also hope that Aussies would be more water-conscious than our European counterparts, but there's no equivalent local study.
How much water you use washing by hand
Still don't believe using a dishwasher is more water-efficient?
Let's look at how much water it takes to wash by hand, starting with how much water it takes to fill your sink. A typical Australian sink ranges from 15 to 45 litres. For argument's sake let's take the median of 30 litres.
Now think about how much you fill your sink when you wash up. If you're settling in for an epic 144-item saga (which makes up a full load in the dishwasher) you're typically going to fill your sink around half to two-thirds full – that's roughly 15 litres – already more than your dishwasher will use, but not too bad, right? Especially compared with the 100 litres from the German study.
The water capacity of a typical sink ranges from 15–45 litres.
But think about the last time you hand washed a dinner party's worth of heavily soiled plates, pots and pans. How many times did you change the water? Twice? Now we're at 45 litres.
You can minimise water changes by pre-rinsing – but rinsing under a running tap sends your water consumption through the roof. If you have a second sink you can fill it and dunk the plates instead, but you're now filling two sinks, not one.
How long are you running cold water down the drain while you're waiting for it to get hot?
There are water wasters at either end of the job, too.
How long are you running cold water down the drain while you're waiting for it to get hot? You can (and should) save this water in a bucket to use for other purposes, but do you?
And do you rinse the soap off your plates after you've washed them? While it's true you can let your plates dry without rinsing the soap off – it's non-toxic after all – again, do you?
And how much water do you use rinsing kitchen sponges when you're done?
Why do dishwashers use less water than hand washing?
Unlike hand washing, dishwashers don't fill sinks with wash water and they only take in water at certain times, then recirculate it around their contents, which means they can be effective with a lot less water. Typically there's an initial rinse (don't pre-rinse your dishes – the dishwasher does it for you, then uses the level of soil in the rinse water to detect how dirty your plates are), one or two wash cycles, and one or two final rinses.
Dishwashers also use rinse-aid to reduce the surface tension of the water, so the final rinse water sheets straight off your plates without needing to rinse detergent residue off. Some dishwashers even store the final rinse water and reuse it for the first rinse in the next cycle, further improving water efficiency.
Is it ever better to hand-wash dishes?
A dishwasher is more water-efficient than washing by hand when you have a full load. If you've only got a few dirty plates or you're in a small household where it's not practical to wait until the dishwasher's full, you're probably better off washing in the sink.
And factoring in wooden chopping boards, chef's knives, non-stick pans and a whole host of other things that you should never put in a dishwasher, washing some items by hand will always have its place.
How to use less water when you don't have a dishwasher
If you have no choice but to hand wash, there are some things you can do to minimise water waste.
Let the dishes pile up
Unless you're a degenerate teenager, the sight of a stack of soiled dishes sitting by the sink will likely send you into an immediate cleaning frenzy.
It's better to let those plates pile up and wash them all at once
But in the interest of our war on water waste, it's better to let those plates pile up and wash them all at once – doing the dishes several times a day will naturally use more water. You'll save time too, as you only need to grab the gloves, fill, empty and wipe out the sink once.
Use a bucket
If you've got a large sink, filling it with enough water to wash up may be excessive. Instead, you can effectively reduce the volume of your sink by putting a bucket or tub inside to wash up in.
Even better, use the saucepan you just boiled pasta in. You've got to wash it anyway – and you can count the time you spend washing up in it as soaking time.
And speaking of buckets, use one in the sink to capture the cold water while you wait for the hot to come through – it's good, clean drinking water, and shouldn't be wasted.
Forget the final rinse
Is your final dishwashing step to rinse the suds off your plates? You don't actually have to. It might seem unpalatable, but the surfactants in washing-up liquids are non-toxic, so it's fine to put your clean but soapy plates straight in the drying rack.
But if you're not keen on that, use the cool water that you saved while your wash water was heating up, so not a drop is wasted.
Re-use the water on your garden
In an increasingly dry country like Australia there's a lot of interest in using grey water from your laundry on the garden, but you can do this with your washing-up water too.
If you're doing the bucket trick then just tip washing-up and rinse water out on the garden when you're done – your plants will thank you for it.
Not using a bucket or tub? Then it's harder but not impossible – scoop or syphon your sink contents into a bucket and carry it out that way.
Tip the washing-up and rinse water on your garden when you're done.
Do an 'office wash'
The 'office kitchen wash' is a good option if you have to clean one or two things – don't fill the sink, just stick your plate under the tap long enough to wet it, squirt some detergent directly on your sponge and start scrubbing. Now give it a quick rinse under the tap again and you're done. As a bonus, your soapy sponge is now wet enough to clean your cutlery or coffee cup without pre-rinsing.
You can even fine tune your technique using two spray bottles – use one for soapy wash water and the other for rinsing. It's hard to wash in warm water this way, but it's also a great technique for caravanning, where you may have a limited water supply.
Grab a great dishwashing detergent
A dud detergent might get your dishes clean, but it'll take more scrubbing, and therefore time. Time's not on your side when you're dealing with a sink full of hot foamy wash water, and you may have to replace the water once it becomes tepid lest it lose its capacity to remove grease.
Choosing a good detergent in the first place can therefore save you time, money and water in the long run.
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