Irrigation · Service

Winterization and spring startup — the two visits that matter

Getting water out before it freezes, and bringing the system back up slowly enough not to break it. Skipping either costs more than the appointment did.

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In short

What is irrigation winterization & spring startup?

Winterization removes water from an irrigation system before it can freeze, expand and split pipe, valves and the backflow assembly. Spring startup is the reverse: refilling slowly, checking every zone, and re-programming the controller for the season. In freezing climates these are the two highest-consequence appointments of the year — a burst mainline discovered in April has usually been leaking since the first hard frost.

Triggers

Signs you need irrigation winterization & spring startup

You live somewhere the ground freezes and the first frost date is approaching
Your backflow assembly is above ground, which makes it the most freeze-exposed part of the system
The system was installed this year and has never been through a winter
You bought the property recently and do not know whether last autumn's shutdown was ever done
A zone that worked last autumn is dead this spring — the classic signature of freeze damage
Your controller has been sitting on last summer's schedule since September

Seeing something not on this list? Browse irrigation problems by symptom →

The job

How irrigation winterization & spring startup actually works

Autumn: shut off the supply and relieve pressure

The isolation valve feeding the system is closed and the mainline pressure is released. On a system with manual drain valves at the low points, these are opened so gravity does most of the work.

Watch for: The main isolation valve left partly open. A trickle of supply into a system you believe is drained is how a mainline freezes solid over a cold week.
Autumn: blow out the lines, zone by zone, within the pressure limit

Compressed air is introduced downstream of the backflow device and each zone is opened in turn — usually starting with the furthest — until the heads stop producing mist. Air pressure is kept within the limits appropriate to the pipe material, and each zone is run only in short bursts.

Watch for: Excessive pressure or a zone left blowing with no water passing through it. Dry air spinning a rotor gear train or heating a nozzle is what wrecks heads during a blowout, and it is entirely a technique problem rather than an equipment one.
Autumn: protect the backflow assembly and controller

The assembly is drained through its test cocks and its ball valves left partly open so residual water can escape rather than being trapped. Above-ground devices get an insulated cover. The controller is set to off or rain-delay rather than unplugged, so it retains its programme. Filters and hose-end timers are emptied and stored too.

Watch for: A backflow assembly left full because the blowout crew never touched it — the most expensive component to replace after a freeze, and the most commonly forgotten.
Spring: open the supply slowly

This is the part with the most damage potential and the least drama. The isolation valve is opened a fraction and the system is allowed to fill over several minutes, so that air is pushed out ahead of the water rather than being compressed and slammed against a closed head.

Watch for: A valve thrown fully open. The resulting surge — water hammer — is the most common cause of spring damage, and it breaks fittings that survived the entire winter intact.
Spring: run every zone and inspect it

Each zone runs while somebody watches it: heads that survived and heads that did not, arcs knocked by frost heave or snow clearance, clogged nozzles, and any wet patch suggesting a split lateral.

Watch for: A startup that consists of turning the water on and leaving. The inspection is the whole value of the visit.
Spring: backflow test and controller programming

Where local rules require periodic testing, spring is the usual time to schedule it. The controller is then set with real run times per zone for early-season conditions, and the rain sensor is verified as working rather than assumed.

Watch for: The system left on last August's schedule. Early-season watering needs are much lower, and a summer programme running in April is a significant and completely invisible waste.

Money

What does irrigation winterization & spring startup cost?

Both visits are short, per-visit services priced mainly by zone count, and are often sold together or inside a maintenance plan. Blowouts cost more than gravity drains because of the compressor. Full ranges are in the Cost Guide.

See the full irrigation winterization & spring startup cost guide — by material, size and region →

Straight answer

When irrigation winterization & spring startup is the wrong call

Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.

You are in a climate that does not freeze. A blowout is unnecessary and the compressed air is doing nothing useful. A pressure and coverage check going into the dry season is the more valuable visit in those regions.
The system is fully drainable by gravity and you know where the drains are. Some systems have drain valves at every low point specifically so a blowout is not needed. If yours is one, you are paying for a compressor you do not need.
You have not resolved who handles the backflow device. If the blowout crew does not touch it and your regular contractor assumes they did, nobody has drained the most vulnerable component. Confirm ownership of that task explicitly.
It is already deep into a hard freeze. If the system has already frozen solid, blowing air through it can propagate damage. At that point the right move is to leave it, and diagnose in spring.
The system is being replaced or redesigned this year. Winterising pipework due to be dug up in the spring is spending money on the part you are about to discard — though the backflow assembly, which usually stays, still needs protecting.

Straight answer

Can I do this myself?

Compressed air is the risk on this job, not the water. Too much pressure ruptures fittings and can launch a pop-up head or a cap with real force; too little volume leaves water behind and gives you a false sense of a job done. Wear eye protection, never stand over a head while a zone is being blown, and never exceed the pressure appropriate to your pipe material.

Reasonable to DIY

A gravity drain-down on a system built with manual drain valves at the low points. If yours has them, this is genuinely straightforward.
Draining and insulating the backflow assembly — test cocks open, ball valves at a partial angle, cover fitted.
Removing and storing hose-end timers, drip filters and above-ground components.
Setting the controller to off or rain mode, and re-programming it in spring.
The spring inspection walk — running each zone and looking at every head.

Call a licensed pro

Compressed-air blowout, unless you own suitable equipment and understand the pressure and volume limits for your pipe. Rental compressors are frequently the wrong specification for this job in one direction or the other.
Any system where you do not know whether drain valves exist.
Backflow testing after startup, where local rules require a certified tester.
Diagnosing a zone that has failed over winter — freeze damage often appears somewhere other than where the water is showing.

Before you sign

What to check when hiring for irrigation winterization & spring startup

What compressor volume do you use, and what pressure do you run for my pipe?

The most diagnostic question you can ask about a blowout. A specific answer referencing your pipe means they have thought about it. Note also that volume matters more than pressure here — an underpowered compressor leaves water behind.
Do you drain and protect the backflow assembly as part of this?

The most expensive freeze failure and the most commonly skipped task. Get a yes or a no, not an assumption.
How many zones do you blow at once, and for how long each?

Zones done one at a time in short bursts is the careful method. Several at once, or one left running dry, is how heads are damaged during winterization.
Is spring startup booked at the same time, and at what price?

Booking the pair usually costs less, and puts you in the diary before the first warm week when everyone calls at once.
At startup, will you run and watch every zone, or just open the valve?

The inspection is the service. If it is not included, you are paying a call-out fee to have a tap turned.
Do you re-programme the controller for early-season conditions?

A system left on last summer's schedule wastes water for weeks before anyone notices. This is the cheapest saving available on the visit.

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Local pros

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Related work

Often done at the same time

Sprinkler Maintenance

The in-season visits between these two

Backflow Prevention Installation

The component freeze damage costs most on

Sprinkler Repair

For what startup uncovers

Smart Irrigation Installation

Automating the seasonal schedule change

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FAQ

Irrigation Winterization & Spring Startup — questions people ask

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Do I really need a blowout, or will draining do?

It depends on how the system was built. Systems designed with drain valves at every low point can be drained by gravity, and a blowout adds little. Systems laid flat, or with laterals that trap water regardless, need air. If nobody can tell you where your drain valves are, assume you need the blowout.

When should winterization be done?

Before the first hard freeze rather than at the first cold night, and book earlier than you think — every contractor in a freezing climate faces the same fortnight of demand. A light overnight frost will not split a mainline; a sustained freeze reaching pipe depth will. Being three weeks early costs nothing; being one week late can cost the mainline.

What actually breaks if I skip it?

Water expands as it freezes, so failures happen wherever water is trapped in something rigid: split fittings, cracked valve bodies, ruptured backflow assemblies and broken head internals. The backflow assembly is usually the worst of these — above ground, full of water, and not repairable once the body cracks. Damage often stays hidden until spring.

Why does the system need to be filled slowly in spring?

Because an empty system is full of air. Opening the supply fully drives that air ahead of a solid column of water into closed heads and fittings, and the resulting shock — water hammer — breaks things that came through winter perfectly well. Cracking the isolation valve open and letting the system fill over several minutes costs nothing and prevents the most common startup failure.

Can I do spring startup myself and only pay for the blowout?

Many people do, and it is a reasonable split — the blowout is the part that needs equipment. But the startup inspection is where you find out what winter did, and finding a split lateral in April rather than in July is worth a great deal. If you do it yourself, run every zone and watch every head rather than just opening the supply.

Does my backflow preventer need testing every spring?

Possibly. Periodic testing is commonly required and spring is when it is usually scheduled, but the interval and the rules are set by your water utility or local authority rather than being uniform. Ask your utility what applies at your address and book the test alongside startup if it does.