Direct answer: A dishwasher that fills then drains usually has one of two problems: the water is siphoning out through a bad drain-hose setup, or the machine thinks it needs to drain because the float or drain path is not behaving normally.
Most likely: The most common fix is in the drain path: a low or kinked dishwasher drain hose, a clogged sink air gap, or debris around the dishwasher filter and sump area.
First figure out whether the dishwasher drains once and stops, or keeps draining and never moves into wash. That split matters. A brief drain can be normal on some machines. A repeated or immediate drain-out usually points to a siphon, blockage, or a float problem. Reality check: a lot of "fills then drains" calls end up being a drain hose issue under the sink, not a failed internal part.
Don’t start with: Do not start by replacing the dishwasher drain pump or control. This symptom is often caused by hose routing, a sink-side blockage, or a stuck float.
You hear the fill, see water in the tub, then the level drops even when the pump is not obviously running.
Start here: Start with the drain hose routing under the sink. A missing high loop or bad hose position can let the tub siphon itself empty.
The drain pump comes on right after fill and pushes water to the sink drain or air gap.
Start here: Check the dishwasher filter, sump opening, air gap, and drain hose for a partial blockage that makes the machine default back to drain.
You hear a steady drain sound, little or no spray action, and the cycle never really gets going.
Start here: Check whether the dishwasher float is stuck up or jammed with debris, making the machine think the water level is wrong.
The dishwasher acts normal sometimes, but after sink use it drains oddly, backs up, or spits at the air gap.
Start here: Look at the sink-side connection, air gap, and disposal inlet area for grease or food buildup restricting the drain path.
When the hose drops too low before rising, the tub can siphon water out after fill. That looks like a drain problem even when the pump is fine.
Quick check: Open the cabinet under the sink and trace the dishwasher drain hose. It should rise high under the countertop before dropping to the drain connection.
A partial blockage can make the dishwasher start a drain, fail to clear properly, and keep returning to drain mode instead of washing.
Quick check: Pull the lower rack, inspect the dishwasher filter area for food sludge, glass, labels, or bone fragments, and check the sink air gap if you have one.
If the float cannot move freely, the dishwasher may fill oddly, stop early, or switch into drain behavior because it reads the water level wrong.
Quick check: Find the float in the tub floor and lift it gently. It should move freely and drop back down without sticking.
If the hose routing and drain path are good but the machine still actively pumps out right after filling, the drain pump may be jammed or electrically stuck on.
Quick check: Listen closely after fill. A true pump-out has a steady motor hum or whir and sends water out forcefully at the sink connection.
Many dishwashers do a short drain at the beginning. You do not want to chase a fault that is actually normal behavior.
Next move: If the dishwasher fills, holds water, and starts spraying, the symptom may be normal startup behavior or an intermittent sink-side drain issue. If it fills and then loses the water without moving into wash, keep going. That is the failure pattern this page is aimed at.
What to conclude: You are confirming whether the machine is truly abandoning the wash cycle or just doing its usual opening drain sequence.
A siphon is one of the most common reasons a dishwasher fills and then seems to drain itself, and it is checked from outside the machine.
Next move: If the dishwasher now holds water and starts washing, the problem was siphoning from bad hose routing. If the hose routing looks right and the machine still actively drains, move on to the filter and sink-side blockage checks.
What to conclude: A self-emptying tub points to hose position. An active pump-out points more toward a blockage, float issue, or drain control problem.
Food sludge, broken glass, labels, and grease buildup can confuse the drain sequence and keep the dishwasher from settling into wash.
Next move: If the dishwasher now fills, keeps the water, and starts spraying, the drain path restriction was the cause. If the drain path is clear and the symptom stays the same, check the float next.
If the float sticks up, the dishwasher can act like the water level is wrong and switch into drain behavior instead of washing.
Next move: If freeing the float changes the behavior, the float was sticking and giving the dishwasher a false water-level signal. If the float moves normally and the dishwasher still pumps out right after filling, the remaining likely issue is the drain pump or a control problem that needs deeper testing.
Once hose routing, blockages, and float movement are ruled out, you need to decide whether the dishwasher is truly commanding the drain pump when it should be washing.
A good result: If clearing a jammed pump or replacing a failed dishwasher drain pump restores a normal fill-and-wash sequence, verify for leaks and full draining at the end of the cycle.
If not: If the dishwasher still drains at the wrong time after the drain path, float, and pump checks, the fault is likely in the wiring or control logic and is no longer a good guess-and-buy repair.
What to conclude: At this point you have ruled out the common external causes. A confirmed pump problem is repairable. A control-side issue needs measured diagnosis, not parts roulette.
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Most often it is either siphoning through a badly routed dishwasher drain hose or reacting to a blocked drain path, stuck float, or drain issue. Start under the sink and in the filter area before assuming an internal electrical failure.
Yes, many dishwashers do a short opening drain to clear leftover water from the previous cycle. The problem is when it fills and then empties again without moving into wash, or keeps draining and never starts spraying.
Yes. If the dishwasher drain hose connects to the disposal, food sludge at that inlet can restrict flow and create odd drain behavior. If the disposal was recently installed, a missed knockout plug can also block the dishwasher drain connection completely.
If the water level drops without a clear drain-pump sound, or the hose routing is low under the sink, siphoning is likely. If you hear a steady pump hum and see water being pushed out forcefully, the dishwasher is actively draining.
Not first. A bad dishwasher drain pump is possible, but it is not the first bet on a fills-then-drains complaint. Check hose routing, the air gap, the dishwasher filter, the sump area, and the float before buying a pump.
If the hose routing is correct, the drain path is clear, and the float moves freely, the remaining issue may be a jammed drain pump or a control-side fault. A confirmed pump problem is repairable. If the pump is not clearly the issue, call for service instead of guessing at electronics.