The overall perimeter of the loop (in feet) will be 1004/f, where f is the frequency in MHz. Since pipe is a larger diameter than wire, this may result in a resonant frequency slightly below the desired freq, but you can always trim the lengths until you get it where you want it.
The impedance of a square loop is around 100 to 140 ohms, so you will need some kind of matching arrangement to get low SWR on the 50 ohm coax.
Instead of a square loop, consider a design where the overall perimeter is the same, but the sides are twice the length of the top and bottom. When fed at the center of the bottom (or top) section, this will give a feedpoint impedance very close to 50 ohms, so you can feed it directly with coax and have a low SWR.
This idea is from a QST article a few years back; I don't remember what issue.