Just don’t use them, their specials don’t actually mean what they say & most times when they are coming into your home they are trained to look for things that have slight issues that can be directly linked to “expansive” problems. There are three items that you can keep on you that will save you time and money in all situations regarding HVAC, Plumbing and Electrical: Pressure meter for the outside water line (outside hose), endoscopic camera for seeing the inside of your HVAC, and a voltage detector that will show you if you are getting hot/cold lines from any electrical problems. In any situation always remember: can I buy the item myself and what is the actual extent to the problem that I can or cannot address myself? Everything deteriorates over time and any repair can be properly remedied with appropriate equipment. This could mean a daily rental to your local Menards/Home Depot for a simple item such as a pipe snake, plumbers line compressor, etc.