Your sprinkler system after turf: cap it, convert it, or keep a zone

01Which zones can go, and which have to stay?

Start at the controller: run each zone for a minute and flag every head it waters. Colorado 811 does not mark private lines such as a home’s sprinkler lines (Colorado 811), so the only map of your system is the one you make. The rest of that morning is in preparing for turf installation day.

Then sort each zone:

02Should the lawn zones be capped at the heads or at the valve?

At the valve, for any zone that ends up under turf.

• Capped at the heads: the heads come out, caps go on, and the zone’s pipe stays in the ground, still on its valve. The sprinklers-to-dripline guide the City of Longmont publishes does it this way and leaves the pipes in place (City of Longmont), but it was written for planted beds, where a leak shows.
• Shut off at the valve: the valve comes out or its outlet line is capped, so no water can reach the pipe under the turf. A turf distributor’s guidance for installers says the valve feeding a removed lawn “must be capped and/or terminated,” and warns that cutting the valve’s wires is not enough, because “it only takes a minute to rewire that valve back up” (Synthetic Grass Warehouse).

The same guidance says threaded caps on heads may leak over time, eroding the soil and leaving depressions in the turf, and that shallow pipe can take a nail or staple. EPA WaterSense puts a 1/32-inch irrigation leak at about 6,300 gallons a month (EPA). On a lawn a leak shows as a green stripe. Under turf the water goes into the ground:

• On clay, the soil swells. The Colorado Geological Survey says expansive clays can swell up to 20% by volume when wet, and lists irrigation water soaking in beside foundations among the landscaping problems on those soils (CGS).
• On collapse-prone soil, it drops. CGS says collapsible soils can lose 10 to 15 percent of their volume when wetted, and names leaking water lines among the causes (CGS).

Either way the turf shows a hump, a soft spot or a sinkhole: see why turf sinks or goes uneven and, for fasteners near pipe, nails or staples.

Ask the installer where each lawn zone will be shut off, and whether any live pipe stays under the turf. A good answer names the valve box, says whether the valve comes out or its outlet gets capped, and includes pulling the heads and deleting the station from the controller.

03How does a lawn zone become drip for the beds that stay?

Once the lawn is gone, a mixed zone becomes all drip. CSU Extension says one sprinkler head can be converted to feed drip with a kit, but the other heads on that zone must be capped “because sprinklers and drip cannot be mixed within the same zone” (CSU Extension).

What a converted zone needs:

• The right parts, in order. CSU lists a permanent drip zone as backflow preventer, control valve, filter, then pressure regulator. Household pressure runs 50 to 60 psi; drip is built for about 20 to 30. The Longmont guide adds a backflow device and pressure reducer in the valve box for each zone converted to drip.
• A new schedule. Drip runs less often and longer; the Longmont guide says typically 15 to 30 minutes, depending on the plants. Replace the old lawn program on that station instead of leaving it to run the drip.
• Trees on their own zone. The same guide says trees shouldn’t share a zone with perennials and shrubs, because tree zones run much longer. For a tree inside the turf, see watering trees after the lawn becomes turf.
• Less water by the house. Longmont tells residents its clay soils absorb water slowly, so heavy watering runs off (City of Longmont). The CGS foundation warning above applies to drip along the house too.

04Should one zone stay to rinse the turf?

Only if you’ll use it. Know what it gets you:

• Rinsing a dog area: it helps, but it isn’t the whole answer to odor; see getting dog urine smell out of turf. Whether watering rules cover a rinse is in do you have to water artificial turf.
• Cooling: in Penn State field plots, watered turf started warming again after about 15 minutes (how hot turf gets).
• The heads: pop-ups left inside the turf poke through it and need the turf cut around them; heads just outside the turf edge, spraying in, leave the turf whole. Ask which your installer plans.

A kept zone is still a live zone, with a valve, a backflow preventer and a fall blowout, and every zone that stays follows your town’s watering rules:

In Windsor’s RainDance neighborhood, irrigation runs on non-potable water billed at $4.53 per 1,000 gallons plus an annual capital fee of $277.68 per unit, charged at the start of the irrigation season (RainDance Metropolitan District). Capping lawn zones cuts the gallons, not the per-unit fee. Other providers are in our water savings guide.

05What do the remaining zones need each fall and spring?

A blowout, for as long as anything on the system holds water. The Longmont guide says to blow out and shut down before the first fall frost. In half of years the first 32°F night comes by about October 7 at NOAA’s Fort Collins station and October 1 at Loveland 2N (Fort Collins, Loveland 2N).

CSU Extension’s winterizing fact sheet (CSU Extension):

• Blow the system out with compressed air; don’t trust drain valves.
• Keep the air at or under 80 psi for rigid PVC and 50 psi for flexible black polyethylene pipe.
• Blow each zone twice in short cycles, then leave it alone: air through dry pipe heats it.
• Never blow air through a pressure vacuum breaker (PVB) or reduced-pressure (RP) backflow device, whose seals can melt.

What turf changes: a zone shut off at the valve is out of the system. A lawn zone capped at every head but still on its valve has no outlet, so air can’t push its water out, and that pipe spends the winter full under the turf.

The backflow preventer. Not legal advice. Colorado’s backflow rule, Regulation 11.39, leaves it to your water supplier to decide what protection a home’s cross-connection needs (5 CCR 1002-11.39), so the answer differs by provider. Fort Collins-Loveland Water District says the PVB is the most common home device and recommends testing single-family irrigation every three years (FCLWD). Windsor says homeowner testing is voluntary for now (Town of Windsor), but its water FAQ says modifying a system with an unapproved backflow device means upgrading it, and names the fall blowout as one cause of the back pressure the device stops (Windsor FAQs). Whether converting zones means a new device depends on the one you have; ask Windsor’s water department before the work.

In spring, EPA WaterSense says to check an in-ground system for frost damage before use. Run each remaining zone and walk the yard: water at the turf edge, a patch that stays wet or soft, or a new hump means a line needs a look before the first full cycle.