Dishwasher drain clogged

[Rhaine86]

Next up to fix: The dishwasher. Forgive me, for again, I don't know the "scientific" names for the parts that I'm referring to. Bear with me!

I've noticed for about a month now that the drain cover at the base of the dishwasher appeared to have some leftover water sitting around it. Both my husband and I didn't think much about it until I noticed that the amount of sitting water has increased lately. So I unscrewed the cover-- and the drain is clearly visible with all kinds of yucky mold/goo/water stuff. Obviously there's a clog somewhere. I have no idea where I go from here. From googling I see that my clog is probably in the house drain line or the airgap (which is what I call the overflow valve)? I looked under the kitchen sink and see a white plastic tube that enters the cabinet from the dishwasher side and connects up to the airgap pipe below the sink.

I'm not sure how I can completely remove this tube-- or if that's what I'm supposed to do?? Not sure what I do next...

[HayZee518]

the dishwasher drain path is from the dishwasher to an air gap above the top of the dishwasher, then down and into the disposal drain nipple or a tailpiece fitting for the dishwasher outlet. that inverted cap in the dishwasher is a high water cutout switch. when you take out the bottom tray, you remove a nut which frees up the tower. beneath this is a plastic or nylon chopper. on the pump shaft is a macerator blade . way down at the bottom is the pump impeller.

[Rhaine86]

From looking around on the 'net- I found that the correct name for what I removed is the "sump entrance screen". That's all I've done because that is directly where the water/gunk can be seen. What is below that I assume is the drain for the dishwasher.

What to do now still puzzles me.

[LazyPup]

Next up to fix: The dishwasher. Forgive me, for again, I don't know the "scientific" names for the parts that I'm referring to. Bear with me!

I've noticed for about a month now that the drain cover at the base of the dishwasher appeared to have some leftover water sitting around it. Both my husband and I didn't think much about it until I noticed that the amount of sitting water has increased lately. So I unscrewed the cover-- and the drain is clearly visible with all kinds of yucky mold/goo/water stuff. Obviously there's a clog somewhere. I have no idea where I go from here. From googling I see that my clog is probably in the house drain line or the airgap (which is what I call the overflow valve)? I looked under the kitchen sink and see a white plastic tube that enters the cabinet from the dishwasher side and connects up to the airgap pipe below the sink.

I'm not sure how I can completely remove this tube-- or if that's what I'm supposed to do?? Not sure what I do next...


While this is a common complaint with dishwashers it may not be a problem at all.

Back in the mid 1980’s when I first got involved in servicing appliances there was only two companies in the USA manufacturing residential dishwashers, Kitchenaide, which is a division of Hobart Industries and D&M manufacturing. D&M did not market dishwashers under their own name, but rather they built dishwashers by contract to all the major appliance manufacturers in the USA, so in essence, no matter which brand you chose, you were ultimately getting a D&M dishwasher with a minor cosmetic change in the exterior appearance or perhaps a slight modification in how the internal baskets were laid out, but in essence all the working parts were identically the same, and even today the overwhelming majority of all dishwashers are still based upon the D&M design.

Years ago there was a health code that required all dishwashers to have 180degF water to sanitize the dishes during the final rinse cycle. (Still required for all commercial dishwashers). While it was common to operate residential water heaters at 180degF in those days when we allowed for the minor heat losses in the pipe from the water heater to the dishwasher it was very seldom that we actually had 180degF water delivered at the dishwasher location. To insure that the dishwasher had the required 180degF water for sanitizing they built a heating element into the dishwasher and to this day, most dishwashers have a circular heating element in the bottom pan that looks very similar to an electric oven-heating element. (Most dishwashers now have an “Energy Saver” switch that disables the heating element to conserve electrical energy consumption)

When they first began installing the heating elements in dishwashers it was soon learned that the additional heat in the bottom of the pan after the water is pumped out was causing the pump motor seal to dry out and it resulted in water leaking through the seal, down the motor shaft into the motor. The solution was to design the dishwasher so that when it pumped the water out, it would leave about 1” of water in the bottom of the pan. In this manner the water lying in the pan would 1. Absorb the excess heat thereby protecting the seal from overheating and 2. Keep the seal wet so it doesn’t dry out and leak.

That solution worked very well to protect the seal and in fact the manufactures do explain the purpose of the standing water in their operators manual, but such is true of all things mechanical, the general public charged ahead and used the machine without ever taking time to read the operators manual. Over the course of time the manufacturers received hundreds upon thousands of complaints that the pumps were not pumping all the water out, which in turn required the manufacturer to respond to each customer one by one to go back and read the information in their instruction manual. Imagine the audacity of a manufacturer asking a homeowner to “read the instructions”; such things are just not done in our society.

The solution here was to raise the floor pan a couple inches, then install a small sump with a grate over the top and the pump & motor attached to the base of the sump. In this manner it still has the slight cushion of water in the sump to protect the pump and motor seals, but being under the grate it is basically “out of sight, out of mind”, however it only works if the drain hose is connected properly.

In accordance with both the manufacturers installation instructions and the Plumbing Codes the drain hose from a dishwasher must immediately raise as high as possible under the cabinets and be secured in place, then drop down to a point lower than the sink trap. This forms what is commonly known as the “High loop”. Ideally the high loop should be placed in the same cabinet space as the dishwasher but due to the design of modern cabinets that is often extremely difficult to do therefore we may run the drain line into the next cabinet space immediately to the right or left of the dishwasher location and form the high loop in that cabinet space. The drain line may then run horizontally near the base of the cabinets until it reaches the final destination where it is to raise up and connect to the DWV(drain, waste & vent) system by means of an “approved indirect waste receptor”.

Under the Uniform Plumbing Code all dishwashers are required to be connected to an “air gap fitting” above the sink. After it is connected to the air gap if there is a disposal we are required to connect the drain line to the dishwasher inlet on the disposal. Under no circumstances may the dishwasher drain line be connected to the DWV (drain, waste & vent) system downstream of a disposal. In an installation where there is no disposal the line is to be connected to a “side inlet tailpiece” directly under the kitchen sink. (In some jurisdictions if the dishwasher is installed in a cabinet immediately to the right or left of the kitchen sink cabinet you may omit the high loop and run the line directly from the dishwasher to the air gap fitting.)

Under the International Residential Code all dishwashers are required to have a high loop as described above. From the high loop the drain line may be connected to a disposal inlet port or directly to the sink drain line, however most local codes will require an air gap if there is no disposal and some local codes require an air gap for all installations. (Check you local AHJ).
Now let us consider your dishwasher specifically. It may be that the water you are seeing has been there right along but you really never noticed it before, but on the other hand, your machine may now be allowing just a bit more water to remain than normal. If this is the case, we must then ask why?

Step 1. Remove the drain line from the disposal inlet port and use a screwdriver to cleanout the inlet port, then reattach the line.

Step two, remove the lines from the air gap and clean the air gap ports as described above. Normally if an air gap is malfunctioning it will cause a lot of water to leak out onto the sink top. There are no repairable parts in an air gap, however air gaps are relatively cheap and easy to replace.

The most common reason has to do with the dishwasher pump impellor. Dishwasher pump impellors are made of plastic and over the course of time as small fragments of broken glass or small bone chips pass through the pump some of the edges of the impellors get rounded off slightly reducing the pump efficiency. While it may be indicating that the impellor is worn I have seen impellors in that condition continue to function for years so I would not be overly concerned at this time.

You can easily test the pump performance by first running the dishwasher through the drain cycle to get as much water out as you can, then disconnect the drain line from your air gap and put the line into a 5gallon bucket. Now pour about 2gal of water into the dishwasher and again run it through the drain cycle. When the cycle is done inspect the sump grate area to see if the water is down below the grate. If so, the pump and the drain line from the dishwasher are okay. If you are still seeing the water lying in the bottom as it is now, you are confronted with a decision. Can you live with that little bit of excess water in your machine or do you want pull the dishwasher out and check the pump discharge ports or perhaps rebuild the pump? Personally, if there is not much water present I would live with it for now.

[Rhaine86]

I guess what bothers me is that it's not just "water". It's like-- moldy black/brown goop in water. And the cover over the whole thing has grown mold on the inside top of it as well. Seems like either something is seriously defective, or there's a problem somewhere.......

[HayZee518]

flush your system with white vinegar and water. the goop is the same crap you will find in a public water fountain's drain. its food residue just sitting in water. the dishwasher's drain especially in the pump is never completely drained even after a pump cycle.

[Rhaine86]

Just came back to say that my "problem" doesn't appear to be a problem at all (with closer inspection).

As you both have stated--- the water that remains seems to be normal, and after closer inspection and a serious attempt to clean the sump entrance screen-- the muck isn't mold at all (I couldn't figure out how mold would grow in a regularly used dishwasher)...but yes, residual food/grease/nasty gross sticky crap!

Not sure if I'll ever be able to get rid of it all but I will try the vinegar trick (I love the many uses of vinegar!). Would you provide a suggestion for how to "flush" the dishwasher??

Thanks to you both!

[LazyPup]

Mix a cup of chlorine bleach in a gallon of water and pour it into the dishwasher, then turn the dishwasher on and let it run through the wash cycle, but stop it before it pumps out. This will thoroughly mix the bleach in the water and circulate it through all the spray arms and spray heads.

Let that bleach water sit in the machine for at least an hour, overnight would be even better, then restart the machine and let it pump out. At this point you have sanitized the machine and its ready to go into normal service.