Viking Repair Bothell, WA home page (206) 202-2799

Dishwasher Parts, in the order water meets them

Drain Pump and Check Valve

Empties the sump at the end of each fill and keeps dirty water from running back in.

Water path through a built-in dishwasher (side section) Water gathers in the sump. The circulation pump drives it up to the lower and upper spray arms; the drain pump pushes it out through a check valve and up a drain hose that loops high under the counter before dropping to the sink drain. The door hangs on a pivot at its foot, held by a spring. 1 2 3

The drain run picked out in rust: the drain pump beside the sump, the check valve, and the hose rising high under the counter before it drops to the sink drain.

  1. Circulation pump and spray arms
  2. Drain pump and check valve
  3. Door hinges, springs and panel mount

Does

At the end of each wash and rinse, the drain pump, a small motor-driven pump beside the sump, pushes the used water out through the drain hose to the sink drain or the disposer. The check valve lets that water leave and closes against anything trying to come back the other way.

Fails like

  • Water left standing over the filter when the cycle ends, sometimes with a hum from under the tub and no sound of draining.
  • Water that drains away, then seeps back into the sump from the sink side, often just after the disposer has run.
  • A cycle that stops partway and will not finish, because the tub never empties.

Replaced when

A pump jammed by a shard of glass or a fruit pit can often be cleared and kept; one with a seized or burnt-out motor is replaced. A check valve that sticks open is replaced rather than cleaned, and never doubled up with a second valve in the line.

Dishwasher standing out of its cabinet opening with the base panel off, the pump and sump assembly, drain hose and wiring exposed, and a wrench on a towel.

Where the water goes after the pump

Out of the pump, the water climbs the drain hose, which has to rise before it falls to the sink drain. Viking’s manuals set that rise as a loop at least 28 inches off the cabinet floor on the VDWU524 and 20 inches on the DFUD042, and warn that without it the machine may not drain properly. A new disposer adds one more trap: the knockout plug in its dishwasher inlet has to come out before the hose goes on, or nothing drains at all.

What we check on the visit

Whether the pump runs and actually moves water, what has lodged in its housing, whether the check valve closes, and whether the hose is kinked, flattened behind the unit or missing its loop. The last three mean bringing the unit forward, which on a panel-ready install is done with the panel on.

Before you call

With the dishwasher switched off, lift out the filters as your use and care guide shows and clear the sump by hand; a blocked filter looks exactly like a failed pump. Then run the sink tap and the disposer for a moment, start a short cycle, and listen for the drain.