I think it won't leak gas if it is turned off. Try to replace the spark ignition system or the burner. Remove the burner and replace it with the working one to check if the burner is the problem.
Does your door have a weather stripper? You can replace the weather stripper or install if it doesn't have any. Steel doors can have magnetic weather stripper.
It is caused by some heavy metals in the water. I am using an alkaline filter for our tap drinking water. You may check your water for alkalinity or other heavy metal like lead, etc.
