Turn your sprinklers back on after the hard freezes are done, not on the first warm weekend. In the Denver metro that usually means late April through mid-May. Turn it on too early and one cold night can crack the backflow preventer you just filled.
Spring 2027: check your water provider first
This year, drought rules may decide for you. Denver Water ended lawn watering after Sept. 30, 2026, and says sprinklers need to remain off in spring 2027 until it sets new rules. That covers everyone who gets Denver Water's water, including Denver, Littleton, Greenwood Village, Wheat Ridge, and parts of Lakewood, Centennial, and Lone Tree. A system can still run for installation, repair, or maintenance, as long as someone attends it the whole time. Thornton's 2026 rules said sprinklers shouldn't be turned on before May 1. Check your provider's current rules before you open the valve. 2026–27 watering rules by provider →
Why waiting matters
Front Range springs are famous for teasing. A string of 70-degree days in April is often followed by snow. The moment you open the irrigation supply, water is sitting in the backflow preventer, the valves, and the lines again. A hard freeze can crack them, just as it would have in December. Lawns that have been dormant all winter don't need much water in early spring anyway; a little moisture from late snow is usually plenty.
A reasonable rule: wait until the overnight lows are reliably staying above freezing. Foothills neighborhoods like Golden, west Arvada, and west Lakewood often need to wait longer than the plains.
Spring startup, step by step
- Check the backflow preventer first. Look for cracks in the body or bonnet, and make sure the small test cocks are closed.
- Close the drain valves if your system has any, and make sure the backflow's own shutoff valves start in the closed position.
- Open the main irrigation supply slowly. Opening it fast slams water into empty pipes (water hammer) and can break fittings.
- Open the backflow's shutoffs slowly, upstream first, then downstream, and let the system fill.
- Run each zone and walk it: look for geysers, pooling, dry spots, and heads that don't pop up or are pointed at the house or the street.
- Set the controller: correct date and time, a fresh backup battery, and a spring schedule. Use the seasonal adjust feature instead of running a summer schedule in April.
Common problems after a Colorado winter
- Cracked backflow preventer: water spraying from the bonnet or body the moment you turn it on. Usually the result of a skipped or incomplete blowout.
- Split pipes and fittings: a soggy patch or a geyser in a zone that wasn't fully cleared last fall.
- Broken heads: snowplows, shovels, and mowers take out heads along driveways and sidewalks every year.
- Valves that won't close: debris in a valve diaphragm keeps a zone running.
Schedule the backflow test at the same time
Many Denver-area water providers require the backflow preventer on your sprinkler system to be tested every year. Startup is the natural time, since the system is being turned back on anyway. If you got a notice from your provider, bring it to the appointment. Backflow testing requirements by water provider →
Watering rules
Most metro water providers had drought rules in 2026: assigned watering days, no watering in the middle of the day, and in Denver Water's case, no lawn watering at all after Sept. 30. Check your provider's current rules before you set the controller. Not sure who your provider is? It's the name on your water bill.
Rather have it done?
We do spring startups across the Denver metro: slow refill, every zone checked, heads adjusted, the backflow preventer inspected, and the annual backflow test if you need it. First test $95 per device for new customers. Book a spring startup →