New water heater shaking and hammering noise in the wall

[jayre]

I had the plumber replace a water heater last week. It's a Rheem 50G power vent unit. Everything was working fine until today when there's hammering noise in our shower wall in the second floor and the water heater in the basement is shaking. What is the cause and what can I do until my plumber can come by?

 

[SHEPLMBR]

Can you take pictures of the water heater?

 

[jayre]

Sure, I'll post it later.