Dishwashers 101, A Primer

I thought it would be useful to explain how modern dishwashers work in general and then add some thoughts after the jump. There is a pretty good description in Repair Clinic, but it doesn't cover everything.

There are a few things that are omitted from the write-up:

• Food Disposer - Medium to higher end units generally come with a built-in grinders (disposers) for  pulverizing larger pieces of food and the like that are rinsed off dishes, pots & pans. These actually do a pretty good job. For those of us on Cape Cod who have to worry about Title V septic systems, these are the only kind of disposers we can use. (There are "septic friendly" garbage disposers which mix bacteria with the particles, but I don't believe they are allowed under Title V.) As I said, these grinders do a reasonably good job and are relatively reliable. They will not, however, grind things like glass, metal, bone, or gristle. Don't ask me how I know this. If you start to hear grinding noises, this could be the problem. (It could also be the pump or pump motor.) Getting at the grinder to clean it involves some disassembly - removing the lower spray arm, filter/drain gate, and plate - and takes about an hour including reassembly if you're handy.
• Filter - A dishwasher recycles the hot, sudsy water to get the dishes clean. Obviously, recycling food particles is counterproductive so various filter setups are used to divert the chunky stuff, either to a grinder or the drain system. There are several types of filter systems and I'm not going to cover them all here except to say that it needs to be cleaned periodically. Your manual should explain the correct procedure.
• Soil Sensor - Medium to high end units have photoelectric soil sensors that can keep a wash cycle going until it judges that all soil has been removed. These actually work fairly well, and, if you have one and don't know it, it may be the reason that some loads seem to take longer, even with the same settings.
• Noise - Modern dishwashers are generally quieter than the units of 20 years ago. This is achieved through a variety of techniques including better sound insulation and quieter motors and mechanicals. Sound volume is measure in decibels (db). The decibel scale is logarithmic, so every 3 db equates to a 2X increase or decrease in volume. 55 db is twice as loud as 52 db. Normal conversation is usually 55 - 60 db. A reasonably quiet dishwasher is 52 db, so you can have conversations in the kitchen while it's running. Keep shelling money out, and they get even quieter. Bosch and Kitchenaid have dishwashers rated at 42 db, in case you have one installed in your bedroom.

Modern, high-end dishwashers can indeed be complex machines, with a fair amount of intelligence and flexibility. The should use less energy and water, and get your dishes cleaner, than that dinosaur under your counter with two buttons and a knob.

More on dishwashers in a future post...