Monday, October 10, 2011

Dishwashers - do they really use less water?

So we've all heard that there was a study done that said dishwashers use less water than washing dishes by hand. I've tried to find the study to have a read of it myself, starting here (please share a link if you have found one).

So far I found:
Washing-up Behaviour and Techniques in Europe
GeschirrspĆ¼len in Europa (I'll need some help to read this one!)
Is a Machine More Efficient Than The Hand?
This vs That - Understanding the Grey in Green

This site again quotes 'the reasearch'
According to researchers, a load of dishes cleaned in a dishwasher requires 37 percent less water than washing dishes by hand.
but then says
However, if you fill the wash and rinse basins instead of letting the water run, you'll use half as much water as a dishwasher would.
Well that's pretty contradictory then, to my thinking. If water efficiency was one of your aims when handwashing, you certainly wouldn't wash the dishes under a running tap! So I want to read the study and see for myself exactly what it was about and what and how it compared things - at a quick glance the lowest amount of water used was 36litres (p.39, table 8)... that's a lot of water... the test participants were asked to wash (p.32) 12 place settings each consisting of
a soup plate, dinner plate, dessert dish,
cup saucer, glass, fork, soup spoon, knife, teaspoon, dessert
spoon and additional serving pieces, in total 140 individual
items of crockery, glasses and cutlery
So I'm going to sit down one night, read the study and then I could work out if I thought it 'fit' with how we do things, and in that sense, whether for us, it would work out better to handwash or dishwasher, for the environment.

What I want to do then, is do my 'Our House' dishwasher/handwashing comparison in terms of water use, detergent use and long term costs. I figure if I stack the dishwasher as I normally would (the water etc used in that cycle is easy enough to work out from the manuf book) then take them all out and wash by hand and record water used, etc and see where I go from there.

When we go bush, we cart all our own water and I am sure that we use MUCH less than a dishwasher would, to wash our dishes AND the water gets re-used in the hand washer for nappies and clothes. I'm handwashing at the moment with the dishwasher out of action, but I plan on doing the comparison once it's back up and running.

... so really it's very dependent on exactly what you're comparing. When we decided to get a double bowl double drainer sink when we renovated the kitchen, people laughed and said 'oh you only need a single bowl if you have a dishwasher'...
well there's a few reasons we still went with the double/double combination
  • because dishwashers don't always work
  • because sometimes there's too much to fit in the dishwasher and you need/want the sink and benches clear
  • stuff that needs handwashing (admittedly, not much here needs that!)
  • so you can wash the baby in one sink and scrub his grotty shirts in the other sink - at the same time (the best stain remover I have found is cold water, Ecologic dish liquid and a nail brush).
  • so you can use one sink for 'bubbles' ("kids put your breakfast bowls/cooking bowls/dinner plates in the bubbles please") so that things don't dry hard on the dishes while they wait for the dishwaher - and the other sink is still free for washing veges, straining pasta etc
  • our sink cost us nothing, from Freecycle :)

Anyway. That's quite apart from why I started this post in the first place.

If you have any relevant links or have done this comparison yourself, please share :)

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