My new water heater is not making hot water. It only lasts for 6 minutes then turns cold.
It is a 30 gallon with 4500 elements. I had an electrician and was told it is not electrical.
Help

Your water heater has a plastic in the cold water side of the heater, it is called the dip tube. If yoou used a torch while installing the heater you may have melted the tube and let it fall into the tank. So what you need to do is turn off the water to the heater and disconnect the cold water pipe and see if you still have this dip tube in the pipe at the top of the heater if not you need to purchase a new tub and be very careful when installing the cold water pipe back to the heater.

One other thing is if you turned the power on to the heater before you turned on the cold water and filled the heater you may have burned up the element.

I agree, best place to start. I think he meant to say you have a plastic tube in the cold side. Soldering can cause this tube to melt if you don't know exactly how to do the job. If you had a pro do just call them back, should get fixed for free. Solder you fitting onto the stub coming out of the tank with the stub removed, them teflon tap and screw it in. You next solder joint should then be far enough above the top of the tank to avoid a repeat