Flow Meter Install, correct gap length?

Got my new Flow Meter installed yesterday. One interesting hiccup, but can’t find a thread on what happened to me, so…

15 year-old irrigation system. Nearly 18" of straight pipe after backflow preventer, 1" copper, no problem. Measured, marked the pipe, measured again. Decided to make the lower pipe cut first. When I finished my last cutter rotation, the 1" copper “popped apart” separating by 3/8". Pipes were under some kind of slight rotational load, perhaps ground settling over time, perhaps not-quite-square and true sweating angles, whatever.

So now… do I make my second cut on the original upper mark? Or remeasure up from the first cut 6 1/4" and re-mark pipe BELOW my careful initial measurements?

Decided that the Flow Meter with Sharkbite connectors attached was an absolute length, would not be changing. I elected to remeasure up 6 1/4" from my first cut so total “gap” in pipe would be exactly 6 1/4" and not the 6 5/8" that would result from using my original measurement, made before when 1" copper pipe was under “rotational stress”.

Wonder if anyone else had their backflow plumbing pop wider after the initial cut? Would it make any sense for Rachio to consider this in future installation guide… “Measure, mark, and make your lower cut. If this cut causes pipe to spring apart, then carefully measure up from this first cut across gap and mark your second upper cut, so total installation “opening” in pipe is exactly 6 1/4” after any rotational installation stress is relieved" or words to that affect.

Seems going with my original upper mark would end up putting “pull stress” on the Sharkbite connectors, I’d rather have the whole plumbing rig pressing them together than slightly pulling them apart.


@jfurrer2 - Put me in the camp to remeasure after the cleaned up lower cut so that there is the desired 6 1/4" gap.