If temperature variations were distinct colors, the water in the tank would display a rainbow with the cold, heavy, liquid on the bottom and various degrees of warmer water moving up the column to the hot water on top, which you need for the dirty dishes.
This disintegrating pipe may also create other issues for you.
How about the situation where you get into a hot shower only to have the water suddenly cool as though you have exhausted the heated water supply within a minute or two?
In this instance, the replacement cold water is entering the unit near the top, where you would normally draw off the hot water, so the hot shower is abbreviated because most of the hot water remains at the bottom of the tank, and not in the place you require it.
A properly maintained dip tube can also help keep the bottom of the tank clean since slightly pressurized water enters just above the tank floor. This also requires the tube to be the correct length.
A shorter tube will allow sediment in the water to settle and remain on the bottom where it may accumulate and literally bake on the hot surface just above the burner.
This is a fairly common dynamic that lowers the heating efficiency of the unit and can contribute to a popping noise from the heater when the burner turns on as expanding air in the accumulation rises into the water.
Sediment buildup can cause higher water heating costs, lowered efficiency and lowered hot water volume.
All of these issues can generally be resolved by periodic draining of the tank, maintenance of the water supply and correct length of tube.
Replacement tubes can be found in most good hardware and big box stores and are generally a PEX type plastic. They are low cost and easily replaced with minimum skills.
Where the cold water enters the heater, there is a pipe nipple which is at the top of the dip tube. With the unit and water supply shut off, and some of the heated water drawn down in the tank, the nipple and tube can be turned out and extracted so that a new tube can be inserted.
The key is to be certain the new tube is the proper length.
Like any such task, it sounds simple until you actually attempt it for the first time.
If your water heater has been diagnosed with a faulty dip tube, simply visit the InsideOutsideGuys.com and find a trusted professional that can conduct the replacement for you.