The dip tube is another name for the cold water inlet. If you are facing the front of the water heater (where the labels are), the cold water inlet is on top. The dip tube is inside the tank on the right hand inlet. The dip tube is a tube that extends to the bottom of the water heater so as you use water, cold water enters the tank at the bottom pushing the hot water up. As your water heater ages the dip tube will break down. When this happens cold water may enter at the middle of the heater pushing hot water from the middle up.
The dip tube test on my water heater?
How to test my dip tube on my water heater Joliet Illinois This image shows the aerator on your faucet (this is the screen that spins off at the outlet of your faucet) If your aerator looks like this submerge the entire aerator in a bowl of vinegar. If the deposits dissolve it is mineral build up if not it can be parts of your dip tube.
The Water heater
If the water heater in your home was built between 1993 and 1996 and you are beginning to find small pieces of plastic in your faucet aerators, shower nozzles and washing machine supply tube, or if your water temperature is suddenly not as warm as it used to be, the source of the problem may be your water heater‘s dip tube.
Over 20 million gas and electric water heaters built between 1993 and 1996 — about 90 percent of all hot water heaters built during this period — contain a defective polypropylene “dip tube.” polypropylene water heater dip tube Aurora Illinois
The water heater dip tube pieces in this example is the white piece of plastic tubing on the screen. I like to describe them like a egg shell pieces.