So, boil half a kettle of water (so it’s not too heavy), and carry it carefully to your gas (propane) cylinders, looking out for tripping hazards, kids toys, the dog etc, please no accidents!
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Now, carefully and slowly pour a thin stream about as wide as a school ruler down the side of the cylinder for 15 - 20 seconds. Carefully ( there’s that word again! ), place the kettle down and with the palm of your hand slide it up the wet section of the cylinder from bottom to top. Where there is liquid propane, the metal will feel cool, and where the metal changes to a fairly warm temperature, that is the liquid level of propane in the cylinder. If the metal is warm/hot and not cool anywhere your cylinder is empty or near empty.
The secret of the slow pour is to get a good amount of heat into the metal, where there is vapour there is nothing to absorb the heat, where there is liquid the heat is absorbed. You should get a nice clear change at the liquid level.
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While you’re there, why not pour a little soapy water over the various connection to check for leaks. As said in a previous answer, if tiny bubbles forming slowly, don’t panic, call a professional gasman. If larger bubbles forming quickly, tell the gasman you need a replacement or service ASAP. To be super safe, you could turn off the valve on top of the cylinder except when using the most demand appliances in your kitchen. It is not safe and probably illegal, depending where you live, to attempt to fix a leak yourself!!
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