©2013 Green Building Advisor. From The Taunton Press, Inc., publisher of Fine Homebuilding Magazine.
Hello GBA community:
I often get questions involving dishwasher selections. Traditionally, my advice was, naturally, Energy Star. More recently, I've questioned this general advice given the user experiences that I've witnessed. The problem statement is thus: I'm seeing wasteful dishwashing practices in all of the homes that I'm involved with. The homeowners all have some brand of high-end, Energy Star rated dishwashers, and all of them pre-wash their dishes because the dishwasher just doesn't do a sufficient job at washing dishes by itself.
The questions are these: Are dishwashers and associated detergents insufficient to the task of washing dishes these days? Are their specifics of water/detergent chemistry that would be result in improved performance with these dishwasher models? Are there specific features that I should look for in addition to Energy Star certification that would help improve model selection (e.g. installed grinder, cycle/rinse specifics)?
Here's the longer background for those who wish to read further:
What I see is that all the dishwashers are used only as dish-sanitizers. The homes' occupants all pre-wash their dishes, usually with sinks full of hot water and soap (at least 10 gallons of 110 degree water). Then they place the pre-washed dishes in the dishwasher for final cleansing.
I inquire about this and recommend that they should simply scrape off the food from their plates and place the dish into the dishwasher. They all invariably state that following this approach results in unclean dishes.
My Own Study:
In that moment with my clients, I received this information politely, but remained secretly incredulous. Since I don't have a dishwasher, I had to use my own mother's dishwashing habits during some holiday visit to study this problem.
I scraped some plates from a holiday dinner, placed them carefully in the dishwasher (a highly-rated brand in terms of performance and efficiency according to Consumer Reports). And, the dishes came out with a soggy crust of particlized food along with a bigger chunks that I didn't quite scrape off.
So I cleaned out all the drain basin and spray nozzles (mostly clean), and tried again, this time on the heavy cycle, and while the dishes were slightly cleaner, they still had to be hand rinsed again to wash off a few bits of crud.
Granted-- this personal study represents one data point (which is by definition not a trend). But, I've heard similar reflections from my clients' experiences.
Other possible factors:
Detergents are all over the place-- usually the standard supermarket brands (not especially 'green' detergents).
Water quality: Between Hetch Hetchy (pretty soft water) and Colorado River (almost too salty for irrigation), we got a range of water chemistries, and this problem seems to be consistent across those categories.
Some literature review that's available on this very site:
Alex Wilson had a nice article about dishwashers a couple of years ago:
My clients (and mother) who try to follow this advice result in unclean dishes.
And, Martin and Robert Riversong provided some interesting points and counterpoints (and poem!!) in this article
Robert properly points out that handwashing *can be more efficient than using a dishwasher. I completely agree, but unfortunately, that's a non-starter for my clients.
Pardon my prolixity in this question, but any thoughts on this from the community?