Adequate Gas Pressure
While the pool heater is in operation, take a look inside the pilot light window, which is usually on the control panel or front of the pool heater. The pilot light should not waver and should be blue in color. If the pilot light is yellow, the air opening in the pool heater is likely restricted and the gas pressure is too high. If the pilot light is low or uneven, the gas pressure is probably too low.
Gas Pressure Regulator
Almost all pool heaters have a gas pressure regulator, which is both preset and sealed to prevent accidental changes in gas pressure. The gas pressure regulator is generally set at 4 inches water column (WC) for natural gas and around 10 or 11 inches WC for propane gas. WC refers to a pressure measurement that is based on an inch-wide tube of water with a hole on the bottom. The taller the water column, or tube, the higher the pressure rating, or WC. Do not attempt to change or open the gas pressure regulator on the pool heater, as this may cause a gas leak or even a potential explosion.
Gas Valve Pipe
Extending between the gas valve and the heater burners is a pipe that has a small pipe plug. You can check the existing gas pressure at this connection point by using a manometer, which is available at many hardware or pool supply stores. Connect the manometer to the pipe plug and take the gas pressure reading, which should read between 3.7 inches and 4.0 inches WC for natural gas and 10.5 inches and 11.0 inches WC for propane gas.
Adjusting the Gas Pressure
If the gas pressure reading is too low or too high when using the manometer, remove the seal on the gas valve adjustment screw. Then turn the adjustment screw in a clockwise direction slightly if you need to increase the pressure or counterclockwise slightly if you need to decrease the pressure. Take another reading with the manometer before making additional adjustments. Always remember to make small, gradual changes to the gas pressure, as large swings in pressure can cause a leak or other possibly dangerous situation. Contact your pool heater manufacturer or another qualified service professional for assistance or with any questions.