Also check that if you don't have any kind of anti drain back valve in the main line. I started hearing this funny noise one evening and turns out it was the suction from the water flowing back from my house into the line to the street because a main had broken somewhere. My water shutoff valve is only a couple feet off the floor so it could have drained the whole water heater. I shut off the valve coming into the house to keep the lines from emptying.
Water heater silcocks come in a 45 degree angle model and with a 90 degree turn valve. While expensive they are handy to buy a couple to screw into aquatainers instead of the plastic valve they come with. You can then attach an old washer hose to your new aquatainer valve and sit it on top of the toilet tank with the hose going into the air vent at the top of the tank so those in the house can just flush and then open the valve to refill the tank for the next person.