My hot water heater is about 3-4 years old I just replaced the elements in it and drained it, I have notice a lot of build up in the bottom of it how do I get that out of there, or do I need too.

It is hard to get the sediment out of a heater but there a couple of things you can try. One connect as hose to the drain faucet at the bottom of your heater. Leave the water pressure on and open the drain valve, let the water run till you see no more deposits coming out.

A better way is to turn off the power, turn off the water supply, take out the bottom element and make you a walking cane shaped crook our of a piece of metal and scrape the sludge out the open where the bottom element was. At just a shot of water if you need it to keep scraping the stuff out.