Irrigation System Plumbing Repair
Spring startup, zone valves, mainline breaks and the damage winter left.
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Water Left in the Lines Is a Spring Repair Bill
Sprinkler piping sits shallower than your water service and is never meant to hold water through an Idaho winter. A blowout pushes compressed air through the system to clear it, an hour's work in October that prevents cracked valve bodies, split manifolds and a broken backflow assembly in April.
Lines are open right now:
(833) 472-2088
October slots book out in September. Earlier is genuinely better.
Season, not schedule
Late September to the first hard freeze. The window is short and it fills.
Zone by zone
Every zone cycled until it runs dry air. Skipping one defeats the job.
Controlled pressure
Too much air destroys fittings and heads. Volume matters more than pressure.
Backflow protected
The assembly is the most expensive thing freeze damage will find.
Background
A separate system, on a separate calendar
In much of the Treasure Valley, large parts of Boise, Meridian, Nampa, Caldwell, Eagle, Star, Kuna, Garden City, Middleton and the Canyon County towns, the water that runs your sprinklers does not come from the same place as the water in your kitchen tap. It arrives through a separate pressurized irrigation line fed from surface water, delivered on a seasonal schedule set by your district, and metered and billed separately from household supply.
That separation is why a blowout is necessary at all. Household supply lines are buried below the frost line and stay full and liquid all winter. Irrigation piping is buried shallow, deliberately, because it only needs to survive the growing season, and when the district shuts delivery off in autumn, whatever water is sitting in your laterals stays there.
Water expands as it freezes. In a shallow pipe with nowhere to go, that expansion cracks PVC laterals, splits poly fittings, breaks zone valve bodies, ruptures the plastic bodies of sprinkler heads and, most expensively, damages the backflow assembly, which is brass, full of small internal parts and mounted above ground where the cold reaches it first.
A blowout removes the water. Compressed air is introduced at the system's blowout port with the supply isolated, and each zone is run in turn until it discharges dry air rather than mist. It is not complicated work. It is work with a deadline.
Not everywhere in Idaho needs this
Outside the Treasure Valley, most communities have no separately-delivered pressurized irrigation at all, sprinklers run off household supply, a well, or ditch water. The freeze risk is still real for shallow sprinkler piping, but the system, the shutoff and the seasonal calendar are different. Say where you are on the phone and we will tell you which applies.
Not sure whether you're on pressurized irrigation? Tell us your street.
The work
Volume, not pressure, and one zone at a time
The most common misunderstanding about blowouts is that they need high pressure. They need volume. A large compressor moving a lot of air at modest pressure clears a zone properly; a small compressor at high pressure moves very little water and risks damaging the system. Excessive pressure is the classic way a well-meant blowout destroys the heads it was meant to protect, plastic gear drives and nozzle bodies do not tolerate it, and neither do the seals in zone valves.
The sequence: the irrigation supply is isolated at the system shutoff so air cannot travel back toward the delivery line. The compressor is connected at the blowout port, downstream of the backflow assembly. Then each zone is opened in turn, usually starting furthest from the compressor, and run until the discharge changes from a spray to a mist to nothing but dry air. Air is introduced with the zone already open, never against a closed valve.
Zones are cycled more than once. The first pass moves the bulk of the water; a second short pass catches what settles back into low spots in the lateral. Then the backflow assembly is handled: test cocks opened, the body drained, ball valves left at a partial angle so any trapped water has room to expand, and insulated covering fitted where the assembly stays in place over winter.
Finally the controller. Set to off or to a rain-delay mode so it does not attempt to run a dry system on a warm February afternoon, and the backup battery checked or removed.
The calendar
Too early wastes the lawn. Too late wastes the system.
The window in the Treasure Valley is roughly late September to the end of October, and it is set at one end by your irrigation district's shutdown date and at the other by the first hard freeze. Neither is under your control, and the second one moves.
A single light frost is not the deadline, a night at thirty degrees does not freeze water in a buried lateral. The deadline is the first sustained hard freeze, several consecutive nights in the low twenties, which reaches shallow pipe and above-ground brass. In an average year that is late October or early November in the valley, and considerably earlier at elevation.
Two practical realities. First, everybody wants the same three weeks, and the trucks doing blowouts are the same trucks doing freeze protection and autumn plumbing work. Booking in early September for a mid-October slot is normal and sensible. Second, if a hard freeze is forecast and your system is still charged, that becomes an urgent call rather than a scheduled one, and at that point availability is genuinely limited.
If you have missed the window and cold has already arrived, still book it. Removing the water stops further damage even if some has already occurred, and the blowout doubles as the inspection that finds what the freeze already broke.
Hard freeze in the forecast and still charged? Say so when you call.
Consequences
The four things that break, in cost order
The backflow assembly. The most expensive item and the most exposed, since it sits above ground. Freezing splits the brass body or cracks internal components, and the failure is usually discovered at spring startup as water fountaining out of the assembly. Depending on the damage it is either a rebuild or a full replacement. See backflow device repair.
Zone valves and the manifold. Plastic valve bodies crack, diaphragms split, and the manifold fittings that join them let go. Symptoms in spring are a zone that will not shut off, a zone that will not turn on, or water surfacing above the valve box.
Laterals and mainline. Split PVC or poly underground, which announces itself as a soft, permanently wet patch of lawn and low pressure across a zone. Repair means excavation, which is why this is the damage nobody wants.
Heads and nozzles. The cheapest item and the most numerous. Cracked bodies, blown seals, heads that weep continuously when a zone runs.
All four are found at spring startup, which is why startup is done deliberately and slowly rather than by simply turning the water back on, see irrigation system plumbing repair. Charging a damaged system at full pressure turns a cracked fitting into an excavation.
Honest advice
When a rented compressor is fine, and when it isn't
Plenty of Idaho homeowners blow out their own systems every autumn without incident, and there is no reason to pretend otherwise. If you are going to, the things that matter are these.
Get enough air. A small pancake compressor cannot move the volume a zone needs; it will produce a satisfying mist and leave water in the pipe. Rental equipment sized for the job is the difference between doing it and appearing to do it.
Regulate the pressure down. Well below the maximum the system can survive, and lower again for systems with plastic gear-drive rotors. This is where most self-inflicted damage happens.
Never introduce air against a closed zone, never leave a compressor connected and running with no zone open, and do not stand over a head while a zone is clearing, heads can eject under air.
Do not skip the backflow assembly, which is the expensive part. And keep track of every zone, including the one behind the shed that only gets used in July.
Where it is genuinely worth calling someone: systems with more than a handful of zones, anything with a pump, properties where you inherited the system and do not know where all the zones or the shutoff are, and any system where the backflow assembly is unfamiliar to you. Also, frankly, any year where the forecast turned before you got to it.
Household freeze protection can share the same visit.
How it runs
A blowout appointment
Forty-five minutes to an hour and a half for a typical residential system, depending on zone count.
Isolate and connect
Irrigation supply closed at the system shutoff, compressor connected at the blowout port downstream of the backflow assembly.
Clear every zone
Zones run in turn at controlled pressure until they discharge dry air, then a second pass to catch water settling back into low spots.
Protect and shut down
Backflow assembly drained and valves set for expansion, insulated cover fitted, controller set off and the system left documented for spring.
Coverage
Where pressurized irrigation applies
Separately-delivered pressurized irrigation is a Treasure Valley phenomenon, Boise, Meridian, Nampa, Caldwell, Eagle, Star, Kuna, Garden City, Middleton and the Canyon County farming towns. Elsewhere in Idaho, sprinklers run off household supply, a well or ditch water, and the winterization work is different.
Questions
Blowout questions
Book in early September for a slot in the first half of October. The work should happen after your irrigation district shuts delivery off and before the first sustained hard freeze, several consecutive nights in the low twenties, not a single light frost. At elevation, bring all of that forward.
Sometimes nothing, in a mild winter with a system that happens to drain well. More often you buy some combination of a cracked backflow assembly, split zone valves, broken heads and a lateral that has to be dug up. The assembly alone typically costs several times what the blowout would have.
Only if it was designed for it, some older systems have manual drain valves at low points, and a few are laid to self-drain. Even then, drains rarely clear everything, because laterals sag between trenching passes and hold water in the dips. Compressed air is the only method that reliably clears those low spots.
Less than people assume, and volume matters far more than pressure. Excessive pressure damages plastic gear-drive rotors, valve diaphragms and fittings, it is the most common way a blowout causes the damage it was meant to prevent. A large compressor at modest regulated pressure is the correct combination.
Usually not, provided the shutoff, the blowout port, the backflow assembly and the controller are all accessible and gates are unlocked. It helps enormously if you can say how many zones there are and whether any are in unusual places. If we cannot reach a zone, it does not get cleared.
Same principle, different setup. The piping still needs clearing, but the isolation point is a household shutoff rather than an irrigation valve, and the backflow protection is usually a different device. This is the normal arrangement outside the Treasure Valley, and it is worth mentioning when you call.
Some are removed and stored, some stay in place drained and insulated. It depends on the type of assembly and how it is plumbed. What matters either way is that the body is empty, the test cocks are opened, the ball valves are left partly open so any residual water can expand, and the unit is covered if it stays outside.
No. The plumber repairs and replaces backflow assemblies, but we do not perform backflow certification testing, that is a separate service with its own requirements, and where testing is required it varies by district and city. Your irrigation provider can point you to who does it locally.
Missed the window? Still worth doing, it finds the damage too.
An hour in October, or an excavation in April.
The blowout is one of the few pieces of plumbing work where the cost-benefit is not arguable. Book it before the calendar makes the decision for you.
(833) 472-2088