It’s that time of year again to start thinking about preparing your irrigation system for winter temperatures. In this part of Texas we continue to irrigate our lawns during the winter, but we still need to protect our systems from freezing.
Protecting Pipes
Because of our milder winter temperatures we don’t need to drain our underground pipes or have them blown out with compressed air. As long as the pipes are buried 8-12 inches deep (below the area’s frost line), the soil should insulate them.
Above-ground pipes, however, do need to be insulated. Use fiberglass pipe insulation to wrap them, or apply self-sticking foam insulating tape. Foam insulating tubes commonly sold at home supply stores also work well.
Valves
Valves buried directly in the ground, or covered by a valve box, are insulated from the cold. Make sure any broken, missing, or open box lids are repaired or replaced.
The isolation valve that shuts off the water supply to the irrigation system from the main water supply needs to be freeze-proof. In an in-ground system the isolation valve is usually buried in a valve box near the meter, and is insulated from the cold.
An isolation valve can also be found indoors, or above ground near the spot where the main water line exits a structure (e.g. basement or garage). If above ground, wrap it with fiberglass pipe insulation wrap or foam insulation wrap, and keep the insulation dry with heavy rubber tape.
Above-Ground Backflow Prevention Assemblies
Dormant lawns still need some irrigation during the winter, and those overseeded with rye grass require regular watering. To continue irrigating over the winter, protect your above-ground backflow prevention assembly (BPA) by wrapping and insulating it.
Insulate the BPA with foam pipe wrap, and use heavy rubber tape to secure it. Alternatively, use self-stick foam insulation tape, or fiberglass pipe insulation wrap. Be sure not to block the air vents and drain outlets. Use a waterproof tape with fiberglass insulation so it doesn’t get wet.
As a further step, cover the BPA with an insulating pouch that opens at the bottom to allow air flow and drainage. You can prevent the pouch from blowing off by securing it to the ground with small stakes. Adding an insulated enclosure on top of the pouch provides further freeze protection. Many of these enclosures look like rocks that blend into your landscaping.
If freezing temperatures catch you unprepared before you’ve purchased insulating materials, use items from your home to temporarily protect your BPA. Wrap it with a sleeping bag, towels, a fleece blanket, or sweatshirts. Duct tape the wrapping in place, and cover the BPA with a heavy-duty garbage bag to keep everything dry. Seal the bag just enough to keep it and the wrapping from blowing off. You can place a small trash can on top to add some extra freeze protection.
Controllers
For cold weather irrigation use the “seasonal adjust” feature on your controller. It will change the zone run times to a percentage of the programmed schedule that’s based on the hottest time of the year.
On wifi controllers the seasonal adjust feature is automatic, and is based on such factors as: the average historical weather data for the current month, the weather from the day before, and the forecast for the next day.
If your lawn is dormant, change the programming to water only once or twice a month.
Sensors
You can add sensors to scheduling controllers to make them “smarter” and upgrade the system. This reduces water waste, and helps make winter irrigation more efficient. Some of these add-ons include:
Rain sensors turn off the system when it starts to rain. They use either a time factor, or a pre-set level of accumulated water. The Texas Commission on Environmental Quality (TCEQ) requires that rain or moisture shut-off devices must be included with all new automated irrigation systems, or with any repairs involving replacement of controllers (30 TAC 344.62 (j)).
Freeze sensors are often combined with rain sensors. They turn off your irrigation system when a set temperature is reached (e.g. 37°F). With some freeze sensors you have a choice of set temperature points (e.g 33°F to 41°F). Some cities in Texas have local ordinances that require both rain/freeze sensors on irrigation systems.
Soil moisture sensors measure the soil moisture content in the root zone before a scheduled watering. They bypass the irrigation cycle if the soil moisture is above a specific threshold. There’s also a soil moisture sensor that includes a freeze shut-off mode. When the soil temperature is near freezing, the soil sensor cancels irrigation until the soil temperature rises.
Wind sensors will stop the irrigation system when the wind reaches a programmed speed. Shutdown speeds are usually adjustable (e.g. 12 to 35 mph).
Hard Freeze Forecasts
According to Dr. John Nielsen-Gammon, a professor in the Department of Atmospheric Sciences at Texas A&M, a hard freeze is when the temperature falls to 28°F or lower, and stays below 32°F long enough to freeze vegetation and cause ice formation in standing water. When a hard freeze is forecast, you need to take extra steps to protect your irrigation system:
- Turn off the water
- Shut off the water supply to the irrigation system at the isolation valve.
- Shut down the controller
- With automatic controllers use the “rain”, “delay watering”, or “off” setting. All your programming will stay intact.
- To shut down some controllers you “suspend” the zones for the desired length of time.
- Drain gear-drive rotor sprinklers
- Gear-drive rotor sprinklers installed above ground will freeze and rupture if the water doesn’t drain out. Built-in check valves in rotors can prevent the water from draining automatically when the system is shut off.
- If the water hasn’t drained, remove the rotors and shake out the water, then replace them.
- Another option is to install a drain valve on the sprinkler supply pipe so you can drain the water out.
Rebates
In Austin, residents may be eligible for a rebate when they install a rain or soil moisture sensor.
Call the experts at South Austin Irrigation at (512) 534-7449 or fill out our Service Request form for professional maintenance and repair to your sprinkler system.
