okpanhandle - 5/15/2016 20:05

There should be a vacuum-air vent at the beginning and end of the line, at every high point, and at 1000' intervals. Whether the last two actually get done or not is a different question. Where I'm from, the high point is more often than not one end of the line, but I have seen vents in the middle of a field that has significant changes in elevation. It's possible to get an air blockage at the high point, causing a spike in pressure. We have a lot of lines that are unused, but filled, at different times during the year, and air vents are mandatory at each riser.

For what it's worth, I've never seen an air blockage or vacuum damage a line, but a properly designed pipeline will last for very long time. Pumping 1000gpm through a 10in line is not the situation to skimp on safety.