Dishwasher Check Valve: Testing + Replacement Guide (2026)
Quick Fix: If your dishwasher drains but dirty water returns to the tub within 30 minutes, a stuck or failed check valve is the likely cause. The valve is in the sump area or drain pump housing. Push the flapper with your finger to test if it moves freely. If your dishwasher is not draining at all, start with our full troubleshooting guide first.
You cleaned the filter. You checked the drain hose. The dishwasher drains fine during the cycle. But 20 minutes later, dirty water is sitting at the bottom of the tub again.
That pattern points to the check valve. It is a small rubber flapper that costs $8-$67 depending on your brand. Replacing it takes 30-45 minutes with basic hand tools.
Tools and Parts You Will Need
Before pulling anything apart, gather these:
- Phillips and flat-head screwdriver
- Needle-nose pliers
- Towels and a shallow pan (for residual water in the sump)
- Flashlight
- Replacement check valve (brand-specific, see Part Numbers section below)
- Optional: multimeter, if you also want to test the drain pump
Before ordering a replacement, locate your dishwasher model number. It is usually on a sticker inside the door or on the side of the tub. Cross-reference that number with the part numbers listed below to get the right valve for your machine.
What Does a Dishwasher Check Valve Do?
A dishwasher check valve (also called a flapper valve or anti-backflow valve) is a one-way gate in the drain path. It allows water to flow out of the dishwasher during drain cycles and prevents it from flowing back in after the pump stops.
The valve sits in the sump area at the bottom of the dishwasher tub, typically at the drain pump inlet. When the pump runs, water pressure pushes the flapper open. When the pump stops, the flapper drops closed under gravity, sealing the drain path.
Most modern dishwashers have a built-in check valve in the pump assembly. Some also use an inline check valve in the drain hose for additional protection. GE refers to theirs as an “anti-backflow wash/drain diverter valve” (see GE anti-backflow valve documentation). A clogged or stuck drain valve causes drainage problems just like blocked filters and kinked hoses do.
The check valve and your dishwasher air gap or high loop work together. The air gap prevents siphoning from the sink side; the check valve prevents backflow from the pump side. If both fail, water returns from two directions.
Some homeowners add an inline check valve to the drain hose itself during drain hose installation. This is a backup, not a replacement for the built-in valve in the pump or sump area.
Video Guide
Video: “Dishwasher Not Draining? Check the Drain Hose Check Valve” by Scott’s Garage
How to Test Your Dishwasher Check Valve
Before ordering a replacement part, confirm the valve is actually the problem. The symptoms overlap with other drainage issues, so test first. If your dishwasher is not draining but there is no visible blockage, the check valve is the part most homeowners overlook.
Symptoms of a Failed Check Valve
- Dishwasher drains during the cycle but water returns 10-30 minutes later
- Dirty or cloudy water at the bottom of the tub after a completed cycle
- Bad smell from the dishwasher, even after cleaning
- Water drains then comes back intermittently
- Tub always has some standing water after every cycle
The telltale sign: water drains normally during the cycle but pools back at the bottom of the tub within 30 minutes. This backflow also causes bad smells because stagnant drain water sits against rubber seals and food debris.
If your pump is running but not draining, that is a different problem. A bad check valve does not stop the pump from working. It allows water to return after the pump has already done its job.
Testing Method 1: Visual Inspection
- Remove the lower rack and spray arm
- Remove the filter assembly to access the sump area
- Locate the check valve (rubber flapper near the drain pump inlet)
- Press the flapper with your finger. As AHS recommends, gently push the valve arm to make sure it moves freely
- The flapper should swing freely in one direction (outward) and resist movement in the other direction (inward)
- If the valve is stuck, stiff, or has debris preventing closure, clean it or replace it
Testing Method 2: Water Flow Test
If you cannot easily access the valve for visual inspection:
- Run a complete wash cycle and let it drain
- Wait 30 minutes without using the kitchen sink or garbage disposal
- Check the tub for returned water
If water has pooled back in the bottom, the check valve is not sealing. This test works well when the valve is inside the pump housing and hard to reach without disassembly.
Testing Method 3: Blow Test (For Removed Valves)
Once you have removed the check valve from the pump housing:
- Hold the valve up to your mouth
- Blow through it in both directions
- Air should pass freely in one direction and be completely blocked in the other
- If air passes both ways, the valve has failed and needs to be replaced
How to Replace a Dishwasher Check Valve
Safety First
- Disconnect power (unplug the dishwasher or flip the circuit breaker)
- Turn off the water supply valve under the sink
- Place towels under the dishwasher to catch residual water
Step 1: Access the Sump Area
Remove the lower dish rack, spray arm, and filter assembly. On most dishwashers, the spray arm twists or pulls off, and the filter lifts or twists counterclockwise.
Step 2: Locate and Remove the Old Check Valve
The check valve sits in the sump area at the bottom of the tub, near the drain pump inlet. The removal method varies by brand:
- GE: Twist or pull the valve from the sump near the pump outlet
- Whirlpool/KitchenAid/Maytag: Remove the sump cover screws, lift the cover, and pull the check valve out of its seat
- Bosch: Access the valve near the pump inlet after removing the filter assembly
Use pliers if the valve is stuck, but be careful not to damage the seat it sits in.
Step 3: Install the New Check Valve
Note the orientation before removing the old valve. The flapper must open outward (away from the tub, toward the drain). Most valves have an arrow or marking showing flow direction. Installing it backward blocks drainage entirely.
- Seat the new valve firmly in position (some snap in, some twist-lock)
- Confirm the flapper moves freely
- Replace any covers or gaskets you removed
Step 4: Reassemble and Test
Put the filter, spray arm, and lower rack back in. Restore power and run a short wash cycle. After the cycle completes, wait 30 minutes and check for returned water. No backflow means the repair worked.
Related problem: If replacing the check valve does not fix the problem, the drain pump itself may be failing. See our dishwasher drain pump guide for testing with a multimeter.
Check Valve Part Numbers and Cost
| Brand | Common Part Number | Approx. Cost | Notes |
|---|---|---|---|
| GE | GE check valve WD12X10189 | $8-$15 | Pump check valve, fits most GE models |
| Whirlpool | Whirlpool check valve parts (675238) | $55-$67 | Includes drain check valve assembly |
| KitchenAid | 675238 (same as Whirlpool) | $55-$67 | Shared platform with Whirlpool |
| Bosch | Varies by model | $15-$30 | Often integrated into pump assembly |
| Samsung | Varies by model | $10-$25 | Check Samsung Parts site with model number |
| LG | Varies by model | $10-$25 | Check LG Parts site with model number |
Whirlpool, KitchenAid, and Maytag share the same check valve platform (part 675238), so one part number covers all three brands.
DIY vs. Professional Cost
| Approach | Part Cost | Labor | Total |
|---|---|---|---|
| DIY | $8-$67 | $0 (30-45 min of your time) | $8-$67 |
| Professional | $8-$67 + markup | $50-$100/hr + $50-$75 diagnostic fee | $100-$250 |
DIY check valve replacement costs $8-$67 for the part and takes 30-45 minutes. Professional replacement runs $100-$250 including diagnostic fee, labor, and parts markup (Fixr, 2026).
When to call a pro: If the check valve is built into the drain pump (common on Bosch and some Samsung models), you need to replace the entire pump assembly. That job involves disconnecting plumbing and electrical connections under the dishwasher. See our dishwasher drain pump guide for pump replacement steps and cost breakdown.
When to replace the dishwasher: If the total repair cost hits 50% of a new unit ($400-$700), buying a new machine makes more sense, especially for dishwashers over 8-10 years old.
FAQ
What does a dishwasher check valve do?
A check valve is a one-way flapper that prevents drained water from flowing back into the dishwasher tub. It opens during drain cycles when the pump pushes water out and closes when the pump stops, blocking reverse flow. Most modern dishwashers have one built into the drain pump or sump area. GE calls theirs an “anti-backflow wash/drain diverter valve.”
Does a dishwasher need a check valve?
Yes. Without a functioning check valve, dirty water can backflow into the tub after draining, contaminating clean dishes and causing odors. The check valve is one of two backflow prevention points. The other is the high loop or air gap on the drain hose.
Where is the check valve on my dishwasher?
In most dishwashers, the check valve is in the sump area at the bottom of the tub, near the drain pump inlet. Remove the lower rack, spray arm, and filter to access it. The exact position varies by brand. Use your model number on PartSelect or RepairClinic to find a diagram for your specific machine.
How do I know if my dishwasher check valve is bad?
The telltale sign is water that drains during the cycle but returns to the tub within 10-30 minutes after the cycle ends. You may also notice bad smells or cloudy water at the bottom. Remove and inspect the valve by hand. The flapper should swing freely in one direction and seal firmly in the other.
Do dishwashers have built-in check valves?
Yes. Most modern dishwashers have a built-in check valve either in the drain pump assembly or as a separate flapper in the sump. Some dishwashers also have a second inline check valve in the drain hose. If your dishwasher has neither, adding an inline check valve to the drain hose during installation provides basic backflow protection.
Still have water problems? Start with our complete dishwasher not draining guide for step-by-step diagnosis covering every cause from clogged filters to failed pumps.