Water heater issues

Hey!
A few days back my friend bought a new water heater and it was actually working fine. But yesterday suddenly it started making weird sounds. She checked all the connections but was not able to figure it out. The main point is she bought the heater a few days back and now it's working in a weird manner. Can someone help us?

You're going to need to reveal a bit more than that! Make & model? Was it new or second hand?

Crystal balls out