Jimbo
Plumber
CA codes do not require the expansion tank, not does the local code here in San Diego. They haven't caught on yet. All manufacturers ( read the details in your Rheem/GE install manual ) RECOMMEND an expansion tank.
Your unit has probably a 40,000 btu burner, where 10 years ago a similar tank may have been 34,000, or even less. The overall efficiciency is also higher. SO, it heats the water faster, thus the expansion becomes an issue, whereas in the past it may not have been.
Your inspector, if you call for a permit, will want to see self-tapping sheet metal screws in the connection of the elbow to the draft hood.
Your unit has probably a 40,000 btu burner, where 10 years ago a similar tank may have been 34,000, or even less. The overall efficiciency is also higher. SO, it heats the water faster, thus the expansion becomes an issue, whereas in the past it may not have been.
Your inspector, if you call for a permit, will want to see self-tapping sheet metal screws in the connection of the elbow to the draft hood.