Good idea there, but take it from me, the deposits that build up harden over time and there is no way any type of air pressure will dislodge the crud. You would basically have to use a sewer snake on a drill to loosen the stuff and unless you got it all out, then rinsed the pipe with a pressure washer, you would end up with the crud in all of your fixtures like faucets, etc. And as far as replacing existing galvanized pope with new, well, if you think copper pipe and fittings are expensive, you would FAINT when you saw what new galvanized costs. And because it's all imported now, I doubt if the quality is as good as the old stuff. One of the reasons old galvanized pipe is so strong and leak free is because of the extra thickness and sealing the deposits give....:laughing::laughing: