I am in Southern California and we have PG&E as our gas supplier. Does anybody know what the pressure should be at our heater?
The manual for your heater that is supplied by your pool builder would have that information in great detail.
If you know your model and make, you can look it up online, and download a manual.
The normal Natural gas pressure is 7 to 9 inches of water measured with a slack tube manometer or about 1/2 psi at the appliance.
1/2PSI = ~14"wc