Why is my BBQ grill flame smaller than normal?

There are three possible reasons. 

• First, many of the preset low pressure regulators available in the marketplace use 1/4"ID hose and some are attached to a propane regulator with a 1/4" NPT (normal pipe thread) outlet on the propane regulator. There is a limit to the volume of gas that can be delivered through this small ID hose at a fixed low propane pressure. If someone has altered the original manufacturer's design and length of hose the pressure and volume of fuel to the burner will be altered.
• A second cause might be the automatic activation of a surge protection device built within the cylinder valve. 
• A third possible cause might be that the tank was overfilled. All propane tanks are now fitted with Overfill Protection Devices (OPD) which are designed to be activated by a float valve. The OPD feature prevents overfilling of the tank by shutting off the valve.
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