Propane Tank Hissing Noise - What could it be?

Propane tanks will sometimes give an indication of a leak by sound. People will describe this noise as a "hissing" noise coming from the tank getting louder as they get closer. Although product release is occurring in some capacity, it might not necessarily be a propane gas "leak". Some of the situations consumers may encounter with propane tank "hissing" are depicted below.

Open propane bleeder valves that are open will sound like a leak but just need to be closed

Open Bleeder Valve

The fixed liquid level gauge (bleeder valve) is required to be opened by the delivery person every time the tank is filled with propane. On occasion, the delivery driver may not completely close the bleeder valve following the filling process or the bleeder valve opening may have been blocked by a small piece of debris from inside the tank that cleared following the drivers departure. If this is the case, simply turning the bleeder valve clockwise will close the valve and stop the flow of gas. This is not unheard of and is easily remedied by simply closing the bleeder valve.

Propane relief valve will make a hissing noise if they open

Relief Valve Actuating

On hot days when the sun is high overhead and a propane delivery has recently been made, the safety relief valve may open slightly allowing excess pressure to vent. If the relief valve is opened, the protective cap will be removed from the top of the valve from the pressure buildup, as pictured to the left. DO NOT LOOK INTO THE RELIEF VALVE OR TAP IT WITH ANYTHING. Doing so may cause the relief valve to open all the way. The relief valve is doing what it was designed to do and on hot, sunny days, propane tanks are subject to excess pressure due to expanding liquid within the tank. One way to remedy the situation is to cool the tank down by spraying water from a garden hose on the surface of the tank. This will generally cause the relief valve to close.