How do I empty and flush a hot water tank?

Turn off water to the water heater (usually on top of tank). On the bottom of the hot water tank, there should b a faucet- hook a water hose to the faucet, putting other end of the faucet outside if possible- turn the knob on the faucet & water should come out---WARNING- the water will b real hot. depending on the size of the tank & how much sludge is in tank, might take a while- once it stops running, you can open the water on top & flush it out. (1 of 2)

(2 of 2) When u feel it is finished, cut off the water on top & wait until water stops coming out of the hose. turn off the knob on the faucet and remove the hose. Turn water back on (top of tank)-watching to make sure the faucet is not leaking.

https://youtu.be/qqaehhGYV_I?t=139

http://www.artofmanliness.com/2016/05/05/how-to-flush-your-hot-water-heater/

First of all, turn off the electricity at the panel or gas. Then take a water hose and hook it up to your water heater, run it outside and open the drain. Let fresh water come in for a bit to stir up any sediment in the bottom. Then turn off the water going into the heater and let it drain out. When you turn off the water, you need to open the hot water side at a sink so air can help drain. When the heater is empty, you take the hose off. Close the drain and then turn on the water to fill it back up. Hope this helps... Good luck!

they have a lot of videos.... https://www.youtube.com/watch?v=TCFCwldQHAs