You might not hear water running from a leak, if there is one.
The top element comes on first so you have hot next the top/exit point. Once that upper volume is hot, it switches to the bottom element which will continue until it heats the rest of the WH tank, then it shuts off, too. If the top element can't reach its setpoint, the bottom element won't ever turn on, but, you should have a small volume of hot water at the top if the top element is actually drawing those 18A and there's no constant flow. A constant flow will result in the WH never getting up to temp if it is high enough volume (doesn't actually need much).