Most people do not have a clue what pressures are coming out of their house Natural Gas and a Liquid Propane tank, let alone what a Column Inch is.
Each Type of Gas is unique but they are all measured the same.
We will start with Natural Gas.
Most homes un the U.S. feed Natural gas from the meter through their own regulator that give you about 6-9 column inches. Each meter standard or industrial will vary to how much they can put out and when you require more pressure.
Most standard meter or 1st level meters or House Meters as they are referred to will be set about 8 column inches and can go to a max of 9 column inches. The column inches relates to actual measured pressure or 8 column inches = less than a single Pound of pressure or .289 PSI (Pounds Per Square Inch).
Your grill and most outdoor BBQ grills require 4 column inches or 1/10th a pound or .144 PSI to function within the recommended ranges. So the purpose of that Square Box regulator that is inserted in EVERY Natural gas grill is to regulate what the grill gets regardless of how much pressure or column inches is fed to the Regulator from your house or source.
If your a little nerdy, you can check out the conversion link here that allows you to convert from Water Column [inch] to Pound / Square Inch or vis versa.
LP or Liquid Propane
Same applies to the Liquid Propane tank and regulator, only the regulator is fed at a higher pressure and the propane is 10 Water Column inches or .361 of a Pound of pressure after the regulator.
Well, what do you do with your Square Box Regulator that was set for Natural Gas, and now you need to feed your grill with different gas? That is pretty easy, but not everyone knows that.
1. Remove the square box regulator and hook the propane tank hose and regulator directly to the grill manifold.
2. If your Square box Regulator has a NG to LP conversion cap on it, then you just follow those instructions.
We have provided you some helpful pictures and links below.
Conversion Tables - Click Here
Square Box Regulator for LP and NG Courtesy of Summersetgrills.
Other stuff that might be helpful