How to Winterize Your Sprinkler System in Reno

Leave water in your sprinkler lines over a Reno winter and it freezes, expands, and cracks something. Usually the expensive something.

Winterizing means shutting off the water and getting every drop out of the lines, valves, and heads. On a system with manual drains, the job takes a few minutes and can save you hundreds in repairs.

Our crews don’t use compressed air. We drain every system completely and protect the backflow device, and this guide walks you through the same steps.

When to winterize sprinklers in Reno

Have it done by the end of October. TMWA’s rule of thumb is Nevada Day or Halloween, depending on the weather. By then the lawn is going dormant and won’t need water until spring.

Reno’s first freeze used to show up in the third week of September. These days the average is the first week of November, 41 days later than in 1970. Don’t bet on the average. In 2024 the first freeze came on October 18.

So watch the overnight lows, not the calendar. If the forecast shows a hard freeze (28 degrees or colder), finish the job before it gets here.

Know your system before you start

Walk the yard first and find three things:

• Backflow prevention device. On most properties it sits above ground. It keeps sprinkler water from flowing back into your drinking water.
• Valve boxes. Look for a large green rectangular lid, flush with the ground. The sprinkler valves are underneath.
• Main shut-off valve. This controls the water going to the sprinkler system. It’s often in its own valve box or in a vertical plastic pipe.

Then look for the drains. A system can have manual drain valves at its low points, automatic drain valves that open when the pressure drops, or both. If you can’t find any, call us before the first hard freeze.

How to winterize a sprinkler system, step by step

Not every system has every part. Skip the steps that don’t apply to yours.

1. Shut off the water supply

Turn the main irrigation valve clockwise to close it. A sprinkler key helps if the valve sits deep in a box. Then run a faucet inside to make sure the house still has normal water pressure.

2. Turn off the controller

Set the timer to off or rain mode. Your watering times stay saved for spring.

3. Drain the system

Open every drain valve by turning it counterclockwise so the water can run out. Then, in each valve box, give the bleeder screw on every sprinkler valve a half turn counterclockwise. Opening every valve lets air in, so the whole system can drain.

4. Drain or remove the backflow device

Turn both flat handles to 45 degrees, halfway closed. With a flat-head screwdriver, turn both test cock screws to 45 degrees as well to let the water out. A full 90 can trap water inside, and 45 lets it drain. If it’s removable, take it off, store it inside, and cover the pipe ends.

5. Insulate exposed parts

Wrap exposed pipes and shut-off valves with foam pipe covers or insulation tape. Leave drain vents and valves uncovered. If the backflow device stays outside, cover it with an insulated backflow bag.

Last, check your water meter. If it still shows water moving, go back over your work. That water is going somewhere, and it isn’t the lawn. While you’re out there, disconnect and drain the garden hoses.

What can go wrong

Here’s what cracks systems over the winter:

• Missing a drain or a valve. One closed drain valve or bleeder screw can leave water sitting in a whole zone. Open every one.
• Leaving the backflow device bare. It sits above ground and freezes first. Bring it inside or cover it.
• Skipping a low spot. Water runs to the low points of the system. If the drain there stays shut, that water freezes and cracks the pipe.
• Leaving drain valves open in spring. An open drain can waste a lot of water with no wet spot to show for it. You’ll find out when the water bill shows up.

If a head cracks over the winter anyway, our guide on how to fix a broken sprinkler walks you through the swap.

DIY winterization vs having us do it

If your system has manual drains at the low points and you know where they are, drain it yourself. You need a sprinkler key, a screwdriver, and a little patience.

Draining gets harder when you don’t know where every drain and valve is, or when the backflow device needs to come off. Miss one and that zone holds water all winter.

We winterize sprinkler systems across Reno and Sparks every fall. We close the main lines, open every drain valve and every sprinkler valve, and make sure the system drains completely. Removable backflow devices come off and get stored inside. The rest get an insulated cover.

While we’re in every valve box, we keep an eye out for leaks. We’d rather find a leaking valve in October than have you find it in April.

Frequently asked questions

When should I winterize my sprinklers in Reno?

By the end of October, or sooner if a hard freeze is in the forecast. Nevada Day or Halloween is the usual target.

Is draining enough, or do I need a blowout?

Draining works when it’s done completely. Open every drain valve and every bleeder screw, and drain or remove the backflow device. That’s how our crews winterize every system.

Do I need to drain the backflow preventer?

Yes. It sits above ground, so it’s the first thing to freeze. Set both handles and both test cock screws at 45 degrees so no water gets trapped. If it’s removable, store it inside. If not, cover it.

Getting help in Reno

Cory’s Lawn Service has looked after Reno and Sparks yards since 2006, and our sprinkler repair team handles fall winterization too. If you’d rather not hunt for every drain and valve, book a fall winterization and let us handle it. Take your weekend back.