Spring Sprinkler Startup in Montana: The Right Order

When should you start your sprinklers in western Montana?

After the hard freezes are behind you and when the landscape actually needs water, not on a calendar date. A charged system that sits through a cold night can freeze in the backflow assembly and the above-ground piping, which is exactly what the fall blowout was meant to prevent. Our guide to frost dates in Missoula and the Bitterroot explains how late spring freezes run in the valleys.

Montana State University Extension's Yard and Garden Water Management MontGuide notes that woody plants need water from early spring through August, so a dry spring may call for hand watering trees and shrubs before the system is safe to charge. Lawns usually wake up on soil moisture from snowmelt, and there is no benefit to watering a lawn that is still dormant and wet.

What should you check before turning the water on?

Walk the system with the water still off. Look at the backflow assembly for cracks, split fittings or missing test cock caps. Look over the heads for any that were knocked over by snowplows, shoveled snow or vehicles; our fall checklist about marking heads before snow exists for this reason. Check that the valve boxes are not full of water or soil. Make sure the controller has power and that its clock and date are right.

Colorado State University Extension's winterization guide notes that many systems have a main shutoff called a stop-and-waste valve that can sit about 5 feet underground and need a long key, and warns not to force it. If it will not turn, stop there rather than snapping the valve.

How should the backflow assembly be opened?

In the right order, slowly. CSU says to close the test cocks and ball valves before pressurizing the system, and to open the ball valves slowly to avoid water hammer damage. For an RP assembly, CSU says the ball valves should be fully closed when the system is pressurized in spring and then opened and closed slowly. In practice, that means making sure the assembly is closed up, bringing water to it gently from the main shutoff, then easing its downstream valve open so the system fills gradually.

This is the step where a half-open valve left from winter causes trouble later. CSU advises leaving a PVB's ball valves half-open over winter; if they are not opened fully in spring, the whole system runs weak all summer. Our low water pressure guide covers that symptom.

Why charge the system slowly?

Because a dry system is full of air, and slamming water into it drives that air ahead at high speed, then stops the water abruptly when it hits closed valves and heads. Our irrigation systems page explains that lines are charged gradually because hitting a dry system with full pressure can damage components. A common approach is to open the first zone manually while the mainline fills, so trapped air has somewhere to go, and only then bring the main up to full pressure.

What does a zone-by-zone walk look for?

Everything winter and last season did. EPA WaterSense's Sprinkler Spruce-Up is a good checklist: inspect for heads that do not pop up fully or are tilted, flag broken heads, check joints between heads and pipe for leaks, check valve boxes for valves that do not close fully, and look between cycles for water pooling on the surface, which can indicate an underground leak. Then direct the heads: EPA recommends aiming for head-to-head coverage and pointing heads away from driveways, sidewalks and walls.

Run each zone long enough to see every head at full height. Note low heads, misting heads, dry gaps and soggy spots. Heads sink over a season and get knocked out of alignment by mowing and foot traffic, so spring is when coverage gets corrected. Our irrigation leak signs guide explains what each symptom usually means.

What about drip zones?

Drip needs its own short routine. CSU's drip irrigation guide says that before the first spring watering you should flush the mainline, clean the filter and check the emitters. If the filter, regulator or backflow device was removed and stored indoors for winter, as CSU recommends for portable head assemblies, it goes back in that order: backflow preventer, control valve, filter, then pressure regulator. Open the end caps, let the line run until it clears, then cap it again. Our drip irrigation guide covers the rest.

How should the controller be set for spring?

Lightly. The schedule that suited July is far too much for May. EPA's watering tips advise adjusting schedules seasonally, avoiding watering in the middle of the day, and stopping when water pools. MSU's MontGuide warns that frequent shallow watering encourages shallow roots, and that one deep watering to fill the root zone is much better than several light ones. If you are on Missoula Water, the city's recommended watering hours from May 1 to September 30 are 6 to 11 a.m. and 5 to 10 p.m., as we cover in outdoor watering in Missoula.

Spring is also a natural time to replace a clock timer with a weather-based controller that adjusts itself through the shoulder season. Our smart irrigation controllers guide explains when that is worth doing.

Does the backflow preventer need its annual test now?

If you are a Missoula Water customer with an underground irrigation system, the utility requires an annual test by a certified tester and notifies customers by mail when one is due; the test has to be done with the system charged. The best time is right after startup, before the season's heavy use. Outside Missoula, ask your water provider. Our backflow testing guide explains the program, and notes that we coordinate with certified testers rather than performing the test ourselves.

What problems should not wait until summer?

Anything that wastes water or leaves part of the landscape dry. A cracked backflow body, a lateral that soaks one area, a zone that will not start, or a zone that will not stop are all worth fixing now; they only get more expensive as the season goes on. Freeze damage found at startup is one of the most common calls on our sprinkler repair list. If you are also planning lawn work, our guide to spring lawn and landscape startup covers the rest of the yard.

What should you write down for next season?

A short record saves time every spring and fall after this one. Note the date the system was charged, which zones needed repairs and what was replaced, any heads that were moved or renozzled, where the drip filters and end caps are, and the type of backflow assembly with its last test date. Add a quick sketch of where each valve box sits, because they disappear under turf and snow.

Keep the controller's zone list current too. If a bed was converted to drip or a lawn area was removed, rename and reprogram the zone so the next person (or the next smart controller) is not watering something that is no longer there. EPA's watering tips suggest inspecting the system monthly through the season for leaks and broken or clogged heads, and a record makes it easy to see what changed.

Can HJ do the spring startup for you?

Yes. Our startup charges the system gradually, opens the backflow assembly in sequence, runs every zone, adjusts and replaces heads, checks drip filters and emitters, sets the controller for the season, and gives you a short list of anything that needs repair. If we blew the system out in the fall, we already know where everything is. This guide is part of our Montana Landscaping, Lawn & Irrigation Guide, and it pairs with our fall sprinkler blowout and winterization service. Call HJ Property Care & Tree Service at (406) 215-7319 or request a free estimate. We work across Missoula and Ravalli counties, from Missoula and Lolo to Florence, Stevensville, Corvallis, Victor, Hamilton and Darby.

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