Chicago draws its drinking water from Lake Michigan and treats it at the Jardine and Sawyer plants, which makes the supply unusually consistent for a city of this size — you get roughly the same water in Rogers Park as in Beverly. Consistent is not the same as soft, though. It runs moderately hard, and a dishwasher is the appliance that notices first.
What scale actually does in there
Scale is not a cosmetic problem. Inside a dishwasher it does four things, and each produces a complaint that gets blamed on something else:
- •It coats the heating element, which insulates it. The machine heats more slowly and stops drying properly, and the owner assumes the heater has failed.
- •It narrows the spray-arm jets from the inside. An arm that looks perfectly clean can be spraying at half pressure. Plates come out gritty on the bottom rack.
- •It restricts the inlet valve orifice, so the machine fills slowly and eventually throws a fill-time error that reads like an electronic fault.
- •It films glassware. That cloudiness is mineral, not detergent, and no amount of extra detergent will shift it.
If you have two of those four at once, the water is the common cause and we will say so rather than replacing parts one at a time.
The setting almost nobody sets
A good number of dishwashers — Bosch, Miele, Siemens, Asko and several others — have a configurable water-hardness parameter buried in a service menu. It tells the machine how aggressively to dose, and on models with a softener compartment, how often to regenerate.
Installers routinely leave it at the factory default. Against Chicago's supply the wrong setting produces exactly the film and spotting people assume is a failing machine. We set it correctly during a visit at no extra cost on models that support it, and it resolves the complaint without a part more often than you would expect.
The free things worth doing first
- •Keep rinse aid topped up. It is not an upsell; it changes how water sheets off glass, which is most of the drying performance on a modern machine.
- •Use tablets formulated for hard water, and do not over-dose. More detergent in hard water makes filming worse, not better.
- •Clean the filter. Every modern dishwasher has one in the sump and it is designed to be removed by hand. A blocked filter recirculates the debris it just captured.
- •Check the spray arms turn freely, and clear the jets with a pin if they look occluded.
- •Run a descaler through an empty machine two or three times a year. On Chicago water that is maintenance, not intervention.
What is a fault and what is design
Two complaints come up constantly and only one of them is a problem.
Damp plastics and cool dishes at the end of a cycle are normal behaviour on a condensation-drying machine, which is what most European-platform dishwashers are. They have no exposed heating element in the tub; they rely on the residual heat of the load and stainless steel walls to condense moisture. Plastics have too little thermal mass to hold that heat, so they stay wet. That is the design, not a defect.
Water standing in the bottom of the tub is a fault, and it is usually the filter, the sump, the drain hose or an air gap rather than the pump.
What we check, in order
We work the water path in the order it actually flows, because a complaint about one stage almost always originates in another:
- Supply — pressure at the machine, inlet screen, valve body.
- Heat — element condition, thermostat, and whether the cycle is calling for heat at all.
- Circulation — wash pump, spray arms, diverter.
- Drain — filter, sump, hose, air gap, and on a multi-unit building, whether the stack is the actual constraint.
In a two-flat or a converted building, that last one matters. A dishwasher draining into a shared original waste line will throw a drain fault while every other fixture in the kitchen behaves normally. We check whether the unit above or below has the same symptom before condemning a pump.
Is it worth repairing?
Usually yes, if the machine is under about eight years old and the fault is a pump, valve, element, filter assembly or door seal. A control board on a budget machine past two-thirds of its life is the case where we will tell you the money is better spent elsewhere. Integrated and panel-ready dishwashers are the exception — replacing one means cabinetry work, so the threshold for repair sits a long way further out.