Its HAUNTED I TELL YOU ! HAUNTED!

I have to assume this is a gas water heater, although you don’t mention which it is. The reason I assume that is that an electric unit only makes a sizzling sound, like bacon frying, when it’s heating water. The gas heaters, if, as a couple of the previous answers have suggested, you live in an area of high calcium, lime content in the water, accumulate this lime in sediment form on the bottom of the tank over the years. When the burner kicks on and heats the water, it heats the calcium buildup too, when the calcium gets to a certain temperature it explodes like popcorn does under heat. The noise can be annoying if it’s audible from the upper rooms, but it’s seldom dangerous. If your unit is making that much noise, it’s unlikely that you’ll get much out of it by draining. The lime accumulates in large chunks in the bottom and the small spigots that the manufacturers put in most tanks won’t let out much of anything bigger than a BB. I’ve taken chunks out of the element holes of electric units the size of a 50cent piece. If if gets too annoying, get a new water heater, and have the installer put in a 3/4″ full flow ball valve as a drain. That will let out large chunks of stuff when it’s drained. That shouldn’t cost more than an additonal $10 – $15. There is no real way to effectively clean a serious lime sediment buildup from a gas water heater.

If the sound is similar to popcorn popping it could be a build up of lime from hard water. This is what happened to our water heater. We rent our water heater so the company came and flushed it out.

True…Needs to be flushed every year.

Sure! This is an easy one. The water in your area is probably high in calcium. After awhile, the calcium deposits build up. Why that makes the water heater make noise, I don’t know, but it’s easy to fix. Don’t waste any money on a plumber!
On the bottom front of the water heater is and ordinary spigot. Just take a garden hose and hook it up to it. Have the other end of the hose drain out in the street. Let it run for about 20 minutes. Turn it off and take off the hose and you are done. This will wash all the calcium out of your water heater. It’ll take about an hour for your water to heat up again. That’s all there is to it. Don’t pay someone $150 to come out and do that.
Good Luck!

some water heaters, will get to the point ware they will start the water to boil, before turning off, resulting to a gurgleing sound inside. If it shakes and vibrates, that is air in the system. you can blow down the system. By that, you attach a hose to the valve on the side of the heater, open the valve and let it run for about a minute then turn it off, looking for water discoloaision.

Calling the plummer dude is not recomended, unless you can afford the rip off