Long Island groundwater is moderately hard — roughly 100 to 180 ppm depending on where you are — and dishwashers are the appliance that shows it first. Before you write off a machine that is leaving film on glasses and grit on plates, work through the three things that cause most of it.
1. The filter, more often than anyone does it
Modern dishwashers are quiet because they no longer have a food grinder. The trade is a filter you are expected to clean. Twist out the cylindrical filter in the base, lift the flat screen under it, and rinse both under the tap with a soft brush.
If that filter is loaded, the machine has been recirculating dirty water over your dishes for weeks. Monthly is right for most households; weekly if you rinse very little.
2. Spray arms and scale
Take the lower arm off — usually a single clip or a quarter turn — and hold it up to the light. Scale narrows the jets from the inside, so a arm that looks fine can be spraying at half pressure. Clear each hole with a straightened paperclip, check the upper arm and the top spinner the same way, and make sure nothing in the racks is blocking either from turning.
While the racks are out, run an empty hot cycle with a cup of white vinegar on the top rack, or a proper descaler if the interior is visibly chalky.
3. Detergent, rinse aid and water temperature
- •Powder and gel struggle in hard water. Tablets with a built-in water softener do measurably better here.
- •Rinse aid is not optional on Long Island. Cloudy glassware is very often nothing more than a rinse-aid reservoir that has been empty for a year.
- •The machine wants incoming water around 120 °F. If the kitchen tap takes forty seconds to run hot, run it before you start the cycle.
- •Skip the pre-rinse. Modern detergents need some soil to work against, and enzyme action is part of how they clean.
Faults that are actually faults
If the filter is clean, the arms spin freely and the dosing is right, then it is a repair. The ones we find most:
- •Water not draining, standing in the base — drain pump, check valve, or a blocked air gap at the sink.
- •Bosch E24, or a drain code on any brand — restriction in the drain path; see the same order of checks as a washer.
- •Circulation pump weak or noisy — dishes clean on the bottom rack only, poor coverage up top.
- •Leaks at the door — a hardened door seal, which is a routine part, or a tub crack, which usually is not worth fixing.
- •Heating element failed — dishes come out wet and the drying stage does nothing. Note that Bosch and Miele condensation-dry models have no visible element and are *supposed* to leave plastics damp; that is not a fault.
- •Water in the base tray tripping a leak sensor (Bosch E15) — find the leak, do not just reset it.
Typical repairs run $180 to $340 with parts and labor. A twelve-year-old machine that needs a circulation pump and a door seal is usually the point where we tell you to buy new instead.
Built-ins and cabinet damage
Dishwashers are the appliance most likely to quietly wreck the cabinet around them, because a slow seep runs under the unit where nobody looks. If you have ever seen water at the toe kick, or the floor in front feels soft, mention it when you book — we pull the unit and check the substrate rather than working blind at the door.