The gas piping from my gas meter comes into my house in a straight 10 foot run to my gas furnace
Two feet from the exterior wall the black pipe has a t connection with a run to a gas dryer. The gas dryer works fine but the 3 year old gas furnace has a supply problem.
The furnace initially ignites okay with a gas pressure reading of 7 but when the burners go to the second stage the gas pressure drops to a .5.
I have been advised that there is a possibility that there is an obstruction in the black pipe. Here are my questions
is it possible that the gas valve adjusting the flame might be bad?
How would the possible obstruction in the black pipe be cleared?
What type of professional should I hire to address this? An HVAC tech or a plumber?
Is black pipe still the only acceptable material used for gas distribution in the home?
Thanks for your help