WDT790SLYM3 Dishwasher Won't Drain – Causes, Tests & Parts to Fix It
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Understanding the Problem
When a Whirlpool WDT790SLYM3 dishwasher fails to drain, used water remains in the tub at the end of the cycle or after cancel/drain commands. The issue can be caused by a simple clog in the filter or drain hose, a stuck check valve or garbage disposal knockout, or a failed drain pump or control that doesn't power the pump. Start with the easy inspections — filters, sump, and the drain hose — before moving to electrical tests. If the filter and visible areas are clear but the dishwasher still won’t pump water out, the most likely culprits are the drain pump motor (electrically failed or blocked), an obstruction in the drain hose/disposal connection, or a failed electronic control/triac that doesn't send power to the pump. Safe troubleshooting proceeds from visual/low-effort checks to component testing and replacement if necessary.
Common Symptoms
Standing water in tub after cycle, dishwasher displays error codes (e.g., F8/F9 or drain-related codes on some interfaces), gurgling sounds, or strong humming without draining.
Common Causes
- Clogged filter, sump or debris trapped in the pump impeller
- Blocked or kinked drain hose or garbage disposal knockout plug not removed
- Failed drain pump motor or electrical fault in the control board/relay
Popular Parts That Fix This Problem
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Helpful Repair Tip
Run a short drain-only cycle while listening at the base of the unit; a working drain pump will make a distinct humming/sucking sound. If there's silence and the motor doesn't vibrate, remove the lower kickplate and test the pump for 120V during a drain command or check pump continuity with a multimeter.
Frequently Asked Questions
How do I check whether the drain pump is bad?
First remove any water and clear the filter and sump of debris. Run a drain-only or cancel/drain cycle and listen: a working pump will hum and you may hear water being pushed out. If there's no sound, remove the lower kickplate and visually inspect the pump and impeller for debris. With the dishwasher unplugged and the pump disconnected, measure continuity across the pump motor terminals with a multimeter — an open reading indicates a failed motor. If you can safely run the machine and measure voltage at the pump during a drain command, absence of 120V suggests an electrical/control problem rather than the pump itself.
How much will it cost to fix a WDT790SLYM3 that won't drain?
Costs vary by cause: clearing a clog or replacing a filter/sump gasket can be low-cost (parts under $30–$80). Replacing the drain pump typically runs $60–$180 for parts plus labor, depending on region. If the control board needs replacement, parts and labor can push the total higher ($150–$400). If you're comfortable with basic tools, many owners can replace the pump or hose themselves and save on labor; always confirm the correct part number for your exact model/serial before ordering.
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