The Seal Tec unit connects to a open roof vent with a adapter and 14 inch duct. It is very low PSI ===.02 PSI. Jayco RV maker will NOT allow us to use a pressure machine for warranty leak checks. They state that if you go to high a PSI, it can blow out certain seal gaskets or Butyl. I say BS on that. Other than Jayco, no other OEM restricts the Seal Tec from being used to find water leaks. IF you remove a window you have lost a test on THAT window. ALL RV's will show some leaks with a smoke or Air pressure test. BUT!!!!!! some leaks are not always where water can get in. There is a leak but rain water cannot flow into that area and get in the RV. You still seal those areas when found. IF I PAID someone to test the unit and it was not fixed, I would demand a free 2nd test and then I would watch while they do it. Doug