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Parts for Whirlpool ET21GKXHN00 Refrigerator - AppliancePartsPros.com

Sounds like drain tube is plugged so that the water from the defrost cycle cannot drain into the drain pan.

I would check that it is clear.
If plugged a turkey baster with warm water, an air compressor with low pressure or a wire can often be used to clear it.

Also check that it is not plugged with dust etc. at the drain pan end.
You might as well clean the condenser/compressor fan and the condenser coils while you are down there.

If it looks like stuff is growing in the tube I would flush it with a 10% bleach solution. This should kill the stuff and let you flush it out. You may have to do this several times, let it sit for 15 minutes or so between flushes.

Be careful that the drip tray does not overflow and empty the drip tray after you are done.

Be sure to unplug the unit while doing this.

Note: that some units go from the drain pan under the evaporator coils directly. Others drip into a funnel like part at the top, back of the fresh food sectuion and then out a drain tube.

I would unplug the unit first. It is just safer.

You will have to remove the food from the freezer just to get at the drain.
I would leave the fresh food side.

Hot water and a hair dryer will speed up melting/unclogging your drain.

If you are in a warm location and do not have a cooler or two just pile the food in some old blankets, towels etc.. It will stay frozen for quite a while