Bosch Dishwasher Not Draining

Autore: nicO (e un altro collaboratore)

While dishwashers are as prone to part failure as other devices, they also require regularly scheduled maintenance. Refer to your owner's manual and this troubleshooting guide to get your machine running.

Note: Before replacing electrical components or hoses, shut off the electrical connection, and turn off the water supply valve to the dishwasher. After removing the drain hose, you'll be able to pull your machine away from the wall.

Check to make sure the last wash cycle completed properly—if your dishwasher has a “Clean” indicator light, it should be illuminated. If not, the wash cycle may have been interrupted. Close the door and press the Start button.

Do you have a new garbage disposal? If the dishwasher is hooked up to a new garbage disposal, verify that the disposal was installed properly and does not still have a knockout plug in the disposer's drain tube.

If you have water gushing out of your air gap, then the plugs were probably left in.

The plug is located right inside the nipple where the drain hose from the dishwasher attaches to the disposal. If it’s not removed, the dishwasher can’t drain properly.
If the plug has been removed, it's possible the disposer is clogged with debris. Clear out the drain tube from any obstructions.

Try running the garbage disposal (if you have one) — it usually shares the same drain as the dishwasher, this can prevent the dishwasher from draining.

Flush with cold water for 20 seconds afterwards to move debris down the drain.

A clogged filter will certainly cause issues with draining. Take the filter out of the bottom of the machine, usually done by twisting anticlockwise and lifting out.

Clean thoroughly and put back, twisting clockwise to lock the filter back in place.

The drain hose transfers dirty water from the bottom of your dishwasher to your garbage disposal or under sink drain connection. Solid debris — food, hair, etc — can accumulate in the drain hose with time, but clogs normally form with broken plastic, stickers or porcelain chips.

Check for a kink in the drain hose that runs from the bottom of your dishwasher to the drain pipe (usually below the sink). Make sure it’s not pinched or kinked. If necessary, replace it with a new hose.
Check for a clog. Remove the drain hose end from the nipple it's connected to below the sink or disposal, put the end in a bucket, then fill and drain the dishwasher to see if a garbage clog will simply blow out.
If that doesn't work, but you see a small dribble of water, you may have to pull the dishwasher out and remove the drain hose in order clean it out or replace it.
- Remember, there's still water in the unit—so put a drain pan under it before removing the hose.
Remove the sump pump screen at the bottom of your dishwasher and remove any materials that shouldn't be there. This screen is usually held in by a couple of screws. Remove the coarse and fine filters and remove all foreign material.

After the drain hose leaves the bottom of the dishwasher the hose passes through a loop on the outside of the machine. The hose then travels to an air gap, check valve, or high loop under your sink before connecting to the garbage disposal or under sink drain connector.

Air gaps are a plumbing standard in some locations and optional in others. Check local codes if you're unsure. Without an air gap, there is a small possibility to syphon sewage contaminants into your drinking water system.

Check your air gap fittings at the sink for any obstructions.

Air Gap units	High Loop units

A new drain pump should only take a few minutes to remove all water from your dishwasher. Taking longer to remove the water or leaving standing water in the machine is a sign of a bad pump. Low humming or squealing noises also point to a pump problem. Pumps can fail both electrically and mechanically. Some models of dishwashers may have separate pumps to drain and circulate the water, so check both pumps. These pumps are normally on the bottom of your dishwasher.

Let's listen to our dishwasher.

A loud buzzing noise indicates a blocked or dirty drain pump.

Underneath the filter is a removable plastic cover over the impeller. This can be pried out using a blunt knife and then lifted out. Check if the propeller moves freely and is clean of debris. Replace the clip and filter.
If the pump is jammed, remove the blockage. You may have to replace the drain pump if there are no blockages.

A scraping sound suggests a damaged impeller or impeller fin scraping against the pump housing. The impeller is inside of the pump and is what moves the water through the system. Replacing the impeller instead of the whole pump may be possible. Inspect the impeller. If it's broken, replace it.

A worn drain pump may also have a hole, crack, or worn bearings causing a leak. Replace the drain pump in this case.

If none of the above sounds are evident, then disconnect the drain pump from the system, and test its continuity. If the measured impedance in Ohm (Ω) between terminals is 15-40Ω, your drain pump is likely fine.

If the pump just hums when it should be running, the entire pump assembly might need to be replaced.Defective Drain Solenoid Valve

Your machine may have a drain solenoid valve, which lets water drain.

Take off the cover plate near the floor and inspect the motor.
- If your motor has two or three wires, then it is a single direction motor. A motor with four wires is a reversing motor. If you have a reversing motor, you can skip this section because it will not apply to your dishwasher.
Use a multimeter set to Ohm (Ω) and check for continuity by placing the probes onto the electrical leads.
- If the solenoid tests negative for continuity or nowhere near 40 Ohm, it will need to be replaced.

If the check valve gets stuck in the closed position, water will not drain. The valve and ball are normally underneath the filters at the bottom of the machine.

Remove the lower rack, sprayer arm and filters.
Inspect and clean your check valve. It may need replacing if washer still will not drain. Some models use a check ball instead of a valve. This ball may be stuck, or need replacing.

The check valve may also be located underneath the dishwasher, just before the drain hose.

If the valve is located under your machine, grab a drain pan and remove the drain hose from the dishwasher.
Check to make sure the valve is clean and opens correctly.

Your dishwasher was designed to run with a dishwasher compatible soap, and will periodically need cleaning. Performing a routine dishwasher cleaning will help keep dishes clean.