In central Texas our mild winter climate makes it unnecessary to winterize our underground irrigation pipes by draining or blowing them out with compressed air. The ground doesn’t freeze very deep here, and the soil insulates the pipes. However, we do experience freezing temperatures and hard freezes, and should make certain preparations to protect our irrigation systems.
Backflow Prevention Assemblies
Backflow prevention assemblies (BPAs) can be turned off and drained, but in order to keep the irrigation system operational during the winter it’s a better option to wrap and insulate them. Wrap the BPA in foam pipe wrap, and tape it with heavy rubber tape for waterproofing. You can also use fiberglass pipe insulation wrap with plastic or heavy rubber tape to keep the insulation dry — it won’t insulate if it becomes wet. Some people prefer to use R-11 fiberglass insulation. No matter what you use, drain the outlets and make sure the air vents aren’t blocked.
Once the BPA is wrapped with some type of insulation, you can then cover it with an insulating pouch that has a bottom opening. Add further freeze protection by placing an insulated enclosure on top of the pouch. Some even look like rocks to blend into the landscape. You can leave the insulation on all year round if you wish — just be sure to check for any damage, and replace it as needed for the next winter season.
The isolation valve for the irrigation system has to be “freeze-proof”. It can be inside a heated room, or if outside, buried below the frost line or wrapped with insulation. Use fiberglass pipe insulation wrap, or foam insulation wrap, and heavy rubber tape to keep it dry.
According to the Texas Commission on Environmental Quality, “all new irrigation systems must include an isolation valve between the water meter and the backflow prevention device” (Title 30 TAC Section 344.62 (k)). Without this valve you’ll have to shut the water off to the whole house whenever you want to work on the irrigation system.
Above-Ground Pipes and Valves
Above-ground pipes have to be insulated. Self-sticking foam insulating tape or fiberglass insulation wrapped around the pipes works well, as do foam insulating tubes. The sprinkler manifold and valves are usually housed in a valve box below ground, but sometimes the valves are above ground, in which case they need to be wrapped and covered with an insulating pouch.
For winter operation, turn your controller to the “seasonal adjust” setting, which changes the zone run times to a percentage of the irrigation schedule for warmer seasons.
If your controller doesn’t already have various sensors, additional ones can be installed to help with efficient winter irrigation.
Rain sensors will turn off your system after a specified amount of rainfall, or as soon as it starts to rain. In Texas, it’s required by the Texas Commission on Environmental Quality (TCEQ) that all new automated irrigation systems, and repairs requiring replacement controllers, must include an approved rain sensor (Title 30 TAC Section 344.62 (j)).
Freeze sensors turn your system off when a specified temperature is reached — usually 35°F. Freeze and rain sensors are sometimes combined.
Soil moisture sensors measure the soil moisture content in the root zone, and either bypass or interrupt the irrigation cycle if the moisture is above a specified amount. If the soil gets too dry, the sensor will turn the cycle back on. Some soil moisture sensors also include a soil freeze sensor that interrupts the irrigation cycle if the temperature dips below 35°F.
Wind sensors interrupt the irrigation cycle if the wind speed exceeds a programmed threshold.
Weather-based smart controllers use local weather information to adjust irrigation schedules and can be set up for daily seasonal adjustments. Some gather information from a publicly available source, some use pre-programmed historic data, and some use real time data collected on site. These controllers skip irrigation cycles based on user-programmed thresholds for rain amounts, freeze temperatures, wind speeds, and soil moisture levels.
Hard Freeze Forecasts
When a hard freeze is forecast (air temperature falls to 28 degrees or lower and then stays below 32 degrees long enough to freeze vegetation and cause ice formation in standing water) take the following steps:
- Turn the isolation valve off to shut off the water supply to the irrigation system.
- Shut down the controller. Depending on the type of controller you have, turn it to the “rain” setting to shut off signals to the valves, or to the “off” setting. On some controllers there is no “off” setting — you suspend the zones for a certain period of time. All your programming will stay intact. For mechanical controllers, turn the selector switch to the “off” position. You’ll lose your settings and will have to reprogram when the freeze is over.
- Drain water out of gear-drive rotor sprinklers installed above ground so they don’t freeze and rupture. If the water doesn’t drain out on its own, you’ll have to install a drain valve on the sprinkler supply pipe. The check valves on many rotors prevent the water from draining out, so in that case you’ll have to remove the rotors, shake the water out, and replace them.
Running Your Sprinkler System During the Winter
Your lawn goes dormant over the winter and doesn’t need to be watered as often. However, you should be irrigating your lawn once or twice a month to maintain a healthy root system that supports new growth in the spring.
Running your system during the winter also prevents the following problems:
- Stagnant water in pipes growing algae that will later clog up sprinklers.
- Sprinkler gaskets and seals drying out and cracking.
- Roots growing into sprinklers.
- Insects crawling into sprinklers and laying eggs.
- Valve diaphragms drying out and splitting.
- Valves getting stuck.
- Dust and dry dirt working their way into sprinklers.
Running your sprinklers in the winter moves stagnant water out of the pipes, lubricates seals and diaphragms, and blows dirt, roots, and insects out of the system.
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.