In article ,
Pavel314 wrote:

The old one has one round pin and two flat blades, with the blades at an
angle to each other and above the round pin. The new one also has one round
pin and two flat blades but the blades are lined up with each other, so I
have to replace the receptacle with one that matches the new plug. Not a
major project, just a minor annoyance and expense.

Paul-

It is common to purchase a new appliance without the electric cord. You
would specify which connector is required for the cord, and purchase the
cord separately. For my dryer, there were two standard versions, "new"
and "old" style. To be sure, I made a photo and printed it to show the
salesman.

Unless your new water heater has a significantly higher current
requirement, it may be easier to change your water heater cord for one
with the correct connector, than to change the outlet. You might be
able to salvage the cord from your old water heater if it is still in
good condition.

Fred