Winterizing a drip irrigation system

Asked September 24, 2020, 4:22 PM EDT

Hello, For years I've been lax about winterizing my drip system, and I keep paying for it with emitters that fail in the spring, apparently because lingering moisture has frozen and damaged the diaphragms. I do take off the end caps of the 1/2-inch lines, let those lines drain and then replace the caps. But I haven't, as some sources suggest, used compressed air to blow out the lines. Some years, I've had to replace a quarter of the emitters. I'm researching compressors and reading up on compressor fittings ... who knew they were so complex! I wondered whether anybody in your shop has some expertise on using compressed air to clear drip system lines. Obviously, I won't need a lot of pressure, so I don't have to buy one of those big-tank things, but I've never owned or worked with a compressor. I will have to figure out how to connect the compressor to my system, somehow, which means adaptors. I run water from an outdoor hydrant through PVC pipe and then into a dozen 1/2-inch lines that distribute water through the 1/4-inch lines to emitters. Each of the 1/2-inch lines has 10 to 25 1/4-inch lines attached (and each line has its own pressure regulator). It's a makeshift system that I've developed over the last 15 years, with standard stuff from Portland Nursery and Home Depot — from the likes of Accu-Drip, Gilmour, DIG ... . It does a decent job of keeping grounds around our bungalow watered. Our lot is 45 feet by 90 feet, with no lawn. Most of the plantings are herbs, flowers and shrubs — and the annual token tomato. Thanks for any help you can provide. Tim Fought Portland

Multnomah County Oregon

1 Response

I located comments from Colorado that may address your question since they deal with frozen ground that we do here in Oregon and are familiar with using an air compressor to drain the system. We have a buried drip system at our home and have not had any issues with frozen lines in the five years that we have lived here. One thought that occurred to me was for to suggest that you invest in plastic sheeting and/or mulch to insulate your garden during the winter months. It can be staked and removed at will if necessary.. Another option if of course to use overhead watering during the summer months in addition to your drip system as a backup. The Washington County Master Association has installed a garden at PCC Rock Campus that uses both types of irrigation in different sections and it has worked well for the trees, shrubs and flowers that have been there for two seasons.
I hope that these comments can be of some assistance to you. It sounds like the constant efforts that you expend to protect your watering system can produce some frustration and you want to be able to fully enjoy the "fruits" of your efforts at the end of the season with minimal extra effort.
"The problem is that some water may still (after blowing the system) be trapped in the pressure regulator after you are finished. And blowout is not always 100%, so water movement in lines later after blowout can accumulate in the pressure regulator - which upon freezing can ruin the pressure regulator. It's always best practice to remove pressure regulators from drip systems over the winter. Drip can be easily drained after removing pressure regulators, any valves (ball or gate valves you might have installed - and are VERY prone to freezing damage), irrigation timers, etc. from the system and opening end caps to allow gravity drainage at both ends of the drip supply. Loosely cap both ends of supply lines once drainage has occurred.

If main drip supply lines are drained (manually - with pressurized air), emitters and other components on the line will drain. Small amounts of water remaining in black poly lines will not cause damage upon freezing - but it has to be a small amount of water. Fully full/charged lines that aren't drained at all in the fall WILL be damaged by freezing - as will emitters on those charged/frozen lines.

So, compressed air winterizing of drip isn't necessary - as long as lines are drained and valves, pressure regulators, etc. are removed."