How To Fix A Leaky Fireplace Gas Valve . But the cost can go higher up to $2,000 if the leak is in an inaccessible area where excavation is needed. This allows you to quickly be able to turn off the gas in case of an emergency. Storing and using portable propane tanks safely Speaking of Safety from speakingofsafety.ca If the smell of gas is overwhelming, leave the house immediately and contact your local gas professionals to shut off the gas. See if you can get a box wrench or a socket on the fitting &. Then take a jumper cable, or a piece of 14/12 ga wire with stripped ends, and connect two contacts, where thermopile is attached to the gas valve: