Winterization & spring startup in Raleigh, NC.

Fall blow-out, spring startup

Water left sitting in irrigation lines and the backflow assembly through a Raleigh freeze can expand, crack the pipe, and split the RPZ — a spring full of repairs from a job that takes an hour in the fall. Done properly, compressed air empties the lines ahead of the first serious freeze — which around here tends to land somewhere in November.

The spring visit runs the process backwards: pressure brought up gradually, every zone inspected for what the cold did, coverage corrected, and the controller reset for the months ahead. Rushing that restart is how a split line gets discovered by the water bill instead of by us.

Choosing the week, at either end of the year

The week you want in Raleigh is late in the year but ahead of the first serious freeze, which in practice usually falls somewhere in November. Going too early costs you a few weeks of watering that a warm autumn would have used; going too late risks the one night that splits a backflow assembly, and that repair costs many times what the blow-out did.

Spring is the more expensive mistake of the two. A system brought back up quickly, with the main opened fast, sends a pressure wave through pipe that has been empty for months. Water hammer breaks fittings that survived the winter perfectly well. Bringing pressure up slowly takes a few extra minutes and prevents a call-out.

We also use the spring visit as an inspection, because it is the first time all year that every zone runs under pressure with somebody watching. Winter damage, settled heads and controllers that lost their schedule all surface in that first full cycle, and finding them in April is considerably cheaper than finding them in July.

The buried pipe is rarely the thing that fails

People picture the damage as a split line under the lawn, and in this soil it seldom is. Buried pipe lies under a blanket of clay that holds its temperature stubbornly, and a cold snap here rarely reaches it.

What is exposed is the backflow assembly: a brass body on a riser, out in the open, full of water and tied to a live main. Water expands as it freezes and brass will not stretch, so something gives. Often it is not the body but the test cocks, small fittings holding a spoonful of water each, which is quite enough. A cracked one is a modest repair; a cracked body is a new assembly, and a fresh test filed with the utility before the system is legal to run.

So the blow-out finishes at the assembly rather than the last zone. Valves left at a partial turn so no cavity is sealed with water in it, test cocks opened, the device drained rather than merely wrapped. See backflow testing.