There is no difference between 150 Lbs/in² of water and 150 Lbs/in² of air. Pressure is pressure.Brainless wrote:lost in boise i am lol im having a hard time getting a straight answer on this ? i have im trying to convert water PSI to air PSI. here is what i am doing i have a 36inch ductual iron pipe, i have had it to 150 PSI with water in it ,so i guess and i got a slow leak so my ? is im going to test it again with air so what would be the right PSI with air to be around the same or is there a conversion chart i could get or look at to help me or pick your brains for my answer all the engineers wont give me a answer or at least a straight one so plz help he out thank u guyz and gals for your time for even reading this plz any help is helpful ty :idea: