</font><font color="blue" class="small">( I would suggest, as others have, that you use a pipe cutter and then mend the cut with a "dresser" coupling (as shown in WhyNot's post). The couplings are readily available, and you don't run as big a risk of filings in your tank if you use the pipe cutter rather than a sawzall, but the sawzall would do the trick too. )</font>
That is the way to go. The proper name a a "Dressler coupling". PVC pipe can also be used as a replacement. I checked with the oil company back when I had to change the location of my tank. They said it worked just fine. Been over 20 years now and no problems.
I jest loves them there PVC pipe&fittings ya kin do anythin with em.
Harry K