5 feet from the inside loft tank. I was not worried about the pressure from the loft tank. It's the pressure from the main building water tank I'm afraid of. I'm on second floor of 3 floors building. I usually fill up the machine when there is mains water since it fills up faster. I think a 20 liter bucket fills up in about a minute.How high is your water tank, from the tap inlet of the water purifier.