Smart Earth Sprinklers

Winterizing an RPZ Backflow Assembly

water backflow system, RPZ device, irrigationAlthough the winters in central Texas are relatively mild, the temperature does drop below 32°F. To maintain irrigation systems during these freezes, you need to winterize and protect the above ground RPZ (reduced pressure zone) backflow assemblies to prevent any trapped water from freezing, expanding, and causing damage.

RPZs can also be turned off and drained, but you need the correct valve setup to do this. Alternatively, you can wrap and insulate them so you can continue using your irrigation system over the winter. Wrap the RPZ side pipes with a foam pipe wrap, and tape them with heavy rubber tape. Some people prefer to use R-11 fiberglass insulation instead. The RPZ valve itself is in the center, so don’t fully wrap it, because water needs to drain from the bottom of the valve.

The best way to protect this center valve is with an insulation pouch that slips over the top of the whole RPZ, but leaves the bottom open. The bag is attached to the ground with some small stakes. To help seal off the wind, a layer of mulch can be added around the base of the pouch.

A type of insulating enclosure, or box, can then be placed over the “bagged” RPZ for extra freeze protection, with another layer of mulch at its base. You can either make these pouches and boxes yourself or purchase them. Some enclosures are in the form of decorative rocks, with foam wall structures, which can be left in place all year round. If you make your own enclosure, you can insulate it with spray foam, or even tape R-11 fiberglass insulation on the inside.

With these safeguards in place, you can run your irrigation system during the winter. Choose to leave them on all year or remove them in the spring when the danger of freezing has passed, replacing them in the fall.

Choosing the right backflow insulation pouch

Here are some tips for choosing the right insulation pouch (also referred to as a bag, blanket, cover, or jacket) for your RPZ assembly:

  1. Measure the RPZ to buy the right size pouch. For height, measure from the ground up to the top edge of the valve. For the width, measure from the outside edge of one pipe to the outside edge of the other one.
  2. Review the specifications and look for the following:
  • R-value. This number indicates the amount of protection from the cold. The higher the R-value the better the protection. Any number above 10 is good for protection from solid frost. If you’re placing a hard enclosure over the RPZ as well, providing a wind break, you can even go lower than 10 for the R-value.
  • UV protection. Make sure the material in the pouch is UV resistant to prevent degradation.
  • Moisture resistance. Get a pouch that’s moisture resistant. Insulation fibers lose their R-value when they get wet, and can rot due to mold and mildew. Heat sealed products are best.
  • Grommets. Look for grommets at the bottom. When it’s windy, you can use these to secure the pouch with zip ties. For security purposes, use wire locks or plastic security seals instead.

Running your system during the winter

During the winter your lawn goes dormant and doesn’t need as much water. However, to maintain a healthy root system that can support new growth in the spring, and for root insulation during the cold weather, you should be watering your lawn once or twice a month. With your RPZ properly insulated and operational, you can use the “seasonal adjust” setting on your controller to adjust the zone run times to a percentage of the summer irrigation schedule. Remember to water only on your assigned days and times.

There are a number of sensors that can be installed to work with your controller for more efficient irrigation that will also help you in the winter:

Rain Sensors turn your system off after a specific amount of rain has fallen. Some types will turn it off as soon as it starts to rain. In Texas, all new automated systems or replacement controllers must include a rain sensor that’s approved by the TCEQ (Texas Commission on Environmental Quality).

Freeze Sensors turn your irrigation system off when a certain programmable temperature is reached. Most people set them for 35°F. Some freeze and rain sensors are combined. 

Weather-based smart controllers use real time local weather data to make adjustments to irrigation schedules. The controller will skip watering cycles based on user-determined thresholds for soil moisture levels, freeze temperatures, rain amounts, and wind speeds. For winter irrigation needs you should change the programming.

Winter irrigation prevents system problems

Winter irrigation not only benefits your lawn, but it can prevent expensive problems in the spring due to system nonuse. Some of these problems include:

  • Sprinklers clogged with dry dirt, dust, and roots
  • Stuck valves
  • Dry, split valve diaphragms
  • Dry, cracked sprinkler seals and gaskets
  • Algae growth in stagnant water
  • Stuck insects in sprinklers

Running your system moves stagnant water out of the pipes, lubricates seals, gaskets, valve diaphragms, and blows roots, dirt, and insects out of the system.

For the very best in sprinkler repair and maintenance, call the pros at Smart Earth Sprinklers at (512) 694-1147.

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