Backflow Preventers: The Device Protecting Your Drinking Water
The device where your irrigation ties into the house supply is the only thing stopping lawn water flowing backwards into your drinking water.
August 18, 2026 · 5 min read
An irrigation system connects to the same supply that feeds your kitchen tap. Sprinkler heads sit at ground level in soil, fertiliser and whatever else is on the lawn.
If pressure in the main drops — a break, a hydrant being used, heavy demand — water can be pulled backwards. The backflow preventer is what stops that.
What it is
A valve assembly on the irrigation supply, usually above ground near where the system ties in. It allows flow one way and physically prevents it the other.
Most jurisdictions require one on irrigation, and many require periodic testing by a licensed tester. Check what applies where you are — requirements differ across North Texas municipalities.
Signs it needs attention
- Water continuously dripping or spraying from the assembly.
- Visible corrosion or a cracked body — freeze damage is the common cause here.
- Low irrigation pressure that appeared suddenly.
- It failed a test.
- Nobody has tested it in years and your jurisdiction requires it.
Freeze damage
The assembly sits above ground and it holds water. A hard North Texas freeze can crack the body or the internal components, and the damage often is not discovered until the system is turned on in spring.
Before winter: shut the irrigation supply off, drain the assembly through its test cocks, and insulate it. An insulated cover costs very little and it prevents an expensive replacement.
Related pressure issues
A failing backflow assembly can restrict flow to the irrigation system. If irrigation pressure dropped and house pressure is normal, the assembly is a good place to look.
If pressure dropped everywhere, that is a different problem — our guides on low whole-house pressure and pressure regulator failure cover it.
Other backflow risks worth knowing
- A hose left in a bucket, a pool, or a container of chemicals. A hose bib vacuum breaker prevents this and costs very little.
- Chemical sprayers connected to a hose.
- Any cross-connection between potable and non-potable water.
Getting it tested or replaced
Testing needs a licensed tester and specific equipment. Replacement is straightforward plumbing. Either way, call (469) 338-5533 and we will tell you what your assembly needs.
Frequently asked
What does a backflow preventer do?
It stops water flowing backwards from your irrigation system into the drinking water supply. Sprinkler heads sit in soil and fertiliser, and a pressure drop in the main can pull that water back without one.
Does my irrigation system need a backflow preventer?
Most jurisdictions require one, and many require periodic testing by a licensed tester. Requirements differ across North Texas municipalities, so check what applies at your address.
Can a backflow preventer freeze?
Yes — it sits above ground and holds water, and a hard freeze can crack the body or internals. Shut the supply, drain it through the test cocks and insulate it before winter.
Why did my irrigation pressure drop suddenly?
A failing or damaged backflow assembly is a common cause when house pressure is normal. If pressure dropped everywhere, the problem is upstream — likely the pressure regulator.