There is a brass assembly somewhere along the side of your house — usually near the foundation, sometimes in a green plastic box at ground level, with two handles and a set of small test fittings. Most homeowners could not name it and have never touched it.
It is your irrigation backflow preventer, and in a hard North Texas freeze it is the component most likely to be destroyed. It sits above ground, it holds standing water, and it is made of brass with internal parts that do not tolerate ice. Replacing one is several hundred dollars and change, and the damage happens on exactly the night when every plumber in Parker County is already booked.
What It Actually Does
Worth understanding, because it explains why you cannot simply remove the thing. Your irrigation system is connected to the same potable water supply that feeds your kitchen tap. Sprinkler heads sit in soil, in contact with fertilizer, pet waste, and whatever else is on the lawn.
If pressure in the city main drops — a water main break, a hydrant opened for a fire, heavy draw somewhere nearby — water can be pulled backward through the system. The backflow preventer is the mechanical check that stops the contents of your yard from being siphoned into your drinking water. That is why it is required, why most Texas municipalities require annual testing of the assembly by a licensed tester, and why it is not an optional component you can delete.
Why It Freezes Before Anything Else
Four things stack against it:
- It is entirely above ground, exposed to air temperature on all sides, with no soil mass moderating it
- It holds standing water between the two shut-off valves even when the system is off
- Brass is a poor thing to freeze water inside — it splits rather than flexes
- The internal check assemblies and relief components are small and precise, so even minor ice damage ruins them
A failed assembly is not subtle. When it thaws, it sprays — sometimes continuously, from the body or the relief port, at full supply pressure. People discover it by water running down the side of the house or an unexplained jump in the water bill.
Winterizing It Properly
A foam cover alone is not enough on a hard freeze, because an insulated enclosure around water that is still sitting in the assembly only slows the inevitable. Getting the water out is what actually protects it.
The correct sequence:
- Shut off the irrigation system at the controller so it cannot try to run a cycle.
- Close the isolation valve on the supply side of the backflow assembly — the handle closest to the house.
- Close the valve on the downstream side as well.
- Open both test cocks part way with a flat screwdriver to let trapped water drain and to break the vacuum.
- Leave the two main ball valves at roughly 45 degrees rather than fully closed. A partly open ball valve has no sealed cavity to hold water, which is where ice does its damage.
- Insulate the assembly — an insulated bag made for the purpose, or foam wrap plus a covering that sheds water. Do not wrap it in a plastic bag alone, which traps moisture against the brass.
- Leave the test cocks slightly open through the winter.
If your system has underground drain valves or you want the lateral lines blown out with compressed air, that is a separate job and worth having an irrigation contractor do. For freeze protection specifically, the assembly itself is what matters most, because it is the expensive part sitting in the cold air.
The Rest of the Outdoor Plumbing
Same night, same freeze, same afternoon of work. Everything above ground that holds water:
- Hose bibs — disconnect every hose first, then insulate. A connected hose is why a frost-proof faucet still bursts.
- Outdoor kitchen sinks and their supply lines — shut off and drain.
- Pool equipment and any above-ground fill line
- Well pressure tanks and exposed pump plumbing in an unheated pump house
- Detached shop and barn plumbing, which is often on an unheated run and routinely forgotten
- Whole-house water filters or softeners installed in a garage on an exterior wall
- Tankless water heaters mounted outdoors — most have built-in freeze protection that only works if the unit has power, so do not kill the breaker
That last one catches people during an outage. An outdoor tankless unit relies on an electric freeze protection element, and in a freeze that comes with a power loss it has no defense.
If It Already Burst
Close the isolation valve on the house side of the assembly immediately. That stops the water while leaving the rest of the house in service — you should not need to shut the whole house down for this.
A split body or cracked bonnet means replacement, not repair. Internal check components can sometimes be rebuilt if the body survived, which is worth asking about because it is meaningfully cheaper. Either way the assembly has to be tested by a licensed backflow tester after the work and the result filed with the water provider in most jurisdictions.
Do It Before the Forecast
Early November is the right time for this in Parker County. The first hard freeze usually arrives somewhere between late November and early January, and the assembly does not care whether you got to it — it only cares whether there is water sitting in it when the temperature drops.
If you would rather have it done and checked properly, call 817-438-6142 for Aledo and Parker County or 817-438-6955 for Fort Worth. It is a short visit now and a considerably longer one in January.
Ready to talk to a licensed plumber?
Call the Aledo dispatch line directly — a live dispatcher answers, not a voicemail tree.
