The short answer
On a Tappan dishwasher this is usually a dirty or hardened door seal rather than a failed pump seal or a cracked sump. The first checks below cost nothing and need no panel off; the one at the bottom of the list is a service call.
What you actually observe
- Water only when the machine is drained — That ties the leak to the drain hose and its connection, not to the fill side.
- Damage to the cabinet floor with no visible puddle — A slow leak at a hose clip that has been running for months.
- NEAR MISS: water inside the machine at the end of a cycle — That is drainage, not a leak.
Causes ranked for this brand, likeliest first
- A dirty or hardened door seal — The gasket seals on a thin lip. Food residue on it, or rubber that has gone hard, opens a path at the bottom corners. First on Tappan because the gasket compound on a value build hardens sooner, so the seal is live well before the machine is old.
- A failed pump seal or a cracked sump — Water arrives under the machine with nothing visibly wrong above it, and it only appears while the pump runs. Next, and relatedly: the pump is the cheapest moving part in a value build, so it is the part that gives up first.
- A loose hose clip or a split hose — The fill and drain connections are under the machine where nobody looks, and a clip that has relaxed weeps slowly. Third on this build, because a full-size unit pushes more water through the same drain path, so a partial restriction shows sooner.
- A tall item deflecting water at the door — A baking tray in the front row turns the spray straight at the door and beats the seal on pressure alone. Bottom of the list on purpose: there is less margin in the design, so a loading habit a bigger machine tolerates becomes a fault here.
The order to work in
- Run a finger right around the seal and look at the bottom corners — Residue and a flattened corner are both visible and both fixable.
- If everything above is clean and dry, the leak is at the pump or the sump — That is where the owner checks end.
- Dry everything under the kick plate, run a cycle and look again — A dry test is the only way to place a slow weep.
Owner checks, in order
- Wash the door seal and its channel with hot soapy water and check it sits proud all round — Replacing a seal is often unnecessary once it has been properly cleaned.
Tools: a cloth, hot soapy waterAbout 15 min
- Take the kick plate off with the power isolated, dry everything, run a short cycle and watch — Watch, do not reach. The point is to see where the first drop forms.
Tools: a screwdriver, paper towel, a torchAbout 30 min
- Reload with nothing tall in the front row and run the same cycle — If it stays dry, the machine is fine and the loading was not.
About 15 min
- STOP HERE: a pump seal or a cracked sump needs the machine out and stripped — A service call, not an owner check.
Read this before you start
Safety
Switch the machine off at its breaker or unplug it before removing the kick plate or any panel, and shut the supply off at the stop tap. A capacitor can hold a charge after the power is off. Never defeat the door latch to watch a cycle run: it holds hot water and a spray arm behind it. Water and a live terminal in the same cabinet is the one combination worth being careful about.
Where the owner fix ends
Call when the seal is clean, the loading is sensible, the machine is level and it still leaks, or as soon as you find water reaching a socket or the cabinet floor. Isolate the power at the breaker before taking the kick plate off, and shut the supply tap before disturbing any connection.
Closest pages to this one
What is deliberately not on this page
This page is about the Tappan dishwasher as a class rather than one family or model line. Where a family-specific page exists it is linked below and it is the better answer. Not here: seal part numbers, sump diagrams and family-specific torque figures.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
