A natural gas regulator works by accomplishing two tasks relating to how natural gas is delivered to your home. The first task is pressure reduction. The gas utility company delivers natural gas to homes through a vast network of pressurized pipes that travel great distances between gas collection sites and the cities and towns that consume the gas. The utility company pressurizes the gas lines to push the fuel through it's network of pipes to reach your home. Once the gas reaches your home, the gas pressure must be reduced to a level that is useful to your appliances. The vast majority of residential natural gas regulators are known as "self-operated" or "direct-operated" pressure reducing valves. The name stems from the fact that the regulator uses it's own internal spring valve mechanism to reduce pressure and needs no other form of energy to operate. Direct-operated pressure reducing regulators precisely adjust the pressure of the gas through a valve that is backed by an adjustable spring. The spring valve pushes against the opposing pressure in the line and allows the valve to open only enough to pressurize the downstream house side to what is needed.
The second task of a natural gas regulator is to normalize the gas pressure entering the home. Gas delivery piping outside the home is not only frequently delivered at a higher pressure than needed, the pressure may also fluctuate. Furthermore, as different appliances are used in the home, gas pressure in the house piping to the appliances could vary and/or diminish completely if it weren't for the gas regulator. A natural gas regulator normalizes the gas pressure by sensing the gas pressure downstream of the regulator and adjusting it's spring valve accordingly to deliver a constant flow of gas. The regulator accomplishes this by a mechanical connection between it's spring valve and a diaphragm chamber that is filled with gas from the outlet (downstream) side. As the downstream side pressure decreases, the diaphragm pushes the spring valve to allow more gas from the inlet side in to normalize the pressure.
Atmospheric Pressure and Venting
A natural gas regulator works by sensing downstream pressure in the piping and registering it with a diaphragm that is balanced against outside atmospheric pressure. As mentioned previously, the diaphragm is connected to a spring valve that regulates the amount of gas passing through the valve and thus the amount of gas pressure in the home. The relationship to atmospheric pressure is important, because this is what allows the regulator to sense the downstream pressure. In the event that downstream pressure exceeds a preset level, the regulator maintains constant pressure by allowing excess gas to escape through the diaphragm mechanism. Since atmospheric pressure depends on what elevation above sea level your home is located, a natural gas regulator typically is adjusted by the gas company so that it is tuned to the local atmospheric pressure and inlet gas pressure so that it can successfully regulate the gas pressure in your home.