It can be tough to determine how much gas is left in the tank attached to your grill. A simple trick? Heat up some water (FYI, it doesn’t have to be boiling, but if it is, proceed with caution), then pour it down the side of your propane tank while it’s completely off and cool. Slide your hand down the outside of the tank. Where the tank is empty, it will feel warm; where there's still propane, it will feel cool to the touch.