Backflow Testing & Prevention
Test and service the valve assembly that keeps irrigation and other hookups from fouling drinking water.
Homeowner guide
Sprinkler Backflow and Winterizing in Commerce City, CO
A sprinkler system connects your lawn to your drinking water. A backflow preventer keeps lawn water from flowing backward, and winterizing keeps it from freezing and cracking.
By the Mile High Express Plumbing team · published
What backflow means
Water normally flows from the main toward your tap. A drop in main pressure can reverse that flow. If your sprinkler lines are filled with fertilizer or standing water, it can be drawn back into the supply.
A backflow preventer is a one-way barrier that stops this.
What the district says
The South Adams County district describes irrigation systems as a source of backflow. Its rules for commercial customers require testing on installation and annually, by ASSE or ABPA certified testers, with reports due by August 31.
The published rules focus on commercial customers. Ask your water provider what applies to a home sprinkler.
Types of devices
Residential systems often use a pressure vacuum breaker or a double check valve. Hose bibs use a small vacuum breaker. Higher-hazard connections use a reduced pressure assembly.
The device type is set by the hazard level and local code.
Backflow devices side by side
The hazard level decides the device.
| Device | Typical home | Remark |
|---|---|---|
| Hose bib vacuum breaker | Outdoor taps | Threads onto the spigot |
| Pressure vacuum breaker | Home sprinkler systems | Must sit above the highest head |
| Double check valve | Lower-hazard lines | Testable |
| Reduced pressure assembly | High-hazard lines | Testable, and tested yearly in commercial use |
Why testing matters
Springs weaken, seals wear and debris keeps a check valve open. Testing finds a device that no longer protects.
A backflow test by a certified tester measures pressure across the checks and files a report if required.
Winterizing the system
Before the first freeze, shut off the water to the system and blow out the lines with compressed air. Drain the backflow assembly and open the test cocks.
Denver's average first freeze is October 7, so schedule in early October.
Signs of trouble in spring
Water spraying from the relief port, a cracked housing, a geyser at a head or weak pressure in one zone points to damage. Refill the system slowly in spring.
A cracked device must be replaced.
Installing correctly
Backflow devices must be installed at the right height and kept clear of mulch and soil. A device that can flood is a risk.
A licensed contractor can install and test it.
Commercial properties
If your property is commercial, the district requires annual testing. Ask your tester to file the report.
See commercial plumbing for help with larger buildings.
A fall checklist
Turn off the controller, close the supply valve to the system, then blow out each zone with compressed air until only mist comes out of the heads. Drain the backflow assembly by opening its test cocks and turning the handles to a half-open position so no water stays trapped inside.
Leave the controller on rain or off mode, and write down the date. If you hire the work, ask whether the technician also checks the device for leaks before draining it. A device that drips all season is worth fixing while it is dry and easy to reach.
Spring start-up
Open the supply valve slowly, a small amount at a time, so pressure builds gently and does not hammer the lines. Walk each zone and look for geysers, broken heads and wet spots. Check the assembly for leaks and for water at the relief port.
If the device is testable and your provider requires a test, schedule it after start-up so the tester sees the system working at normal pressure. Keep the report with your records.
Hose connections count too
The same idea applies to outdoor hose connections. A hose left in a bucket, a pool or a bottle of fertilizer sprayer can pull that liquid back toward the house if pressure drops. A small vacuum breaker on the spigot costs very little and does the job.
Unscrew hoses at the end of the season anyway. Water left in a hose and spigot freezes, and a split spigot often goes unnoticed until spring. Denver's average first freeze is October 7, so the reminder belongs on the calendar for early October.
What happens if you skip the blowout
Water left in the pipes expands when it freezes. Sprinkler lines are often shallow, and plastic fittings, valves and heads crack under that pressure. The damage stays hidden until spring, when a zone will not hold pressure or water sprays from a split pipe.
Repairs mean digging, replacing valves and fixing fittings, and a cracked backflow assembly has to be replaced. A short blowout visit in the fall costs far less than that repair.
Choosing a contractor
Ask whether the technician holds a current backflow tester certification if testing is part of the visit. Ask what air pressure and volume the compressor delivers, since a small compressor leaves water in the lines.
Ask the contractor to write down the date of service and any problems found. A short report is useful if the utility asks for proof of testing.
Questions to put to your water provider
Call the number on your water bill and ask three things: whether your property needs a backflow assembly, how often it must be tested and who may perform the test. Ask whether the test report needs to be filed and where.
The answer can differ by address and by if you are a home or a business customer. Getting it in writing saves a second call. If your provider is a municipality or a district other than the one serving your neighbors, the rules can differ even across the street, so ask about your own address.
Common questions
Sprinkler backflow questions
Before the first hard freeze. In Denver the average first freeze is October 7.
Ask your water provider. The district's published rules focus on commercial customers.
Only a certified tester. The district requires ASSE or ABPA certification for commercial testing.
It may be damaged. Shut off the water and get it repaired.
Services that help
Commercial Plumbing
Plumbing help for restaurants, shops, offices and multi-unit buildings.
Water Line Repair & Replacement
Fix or replace the buried supply pipe running from the meter to your home.
Keep reading
Outdoor spigot leaking
A dripping hose bib wastes water, and a frozen one can split the pipe inside the wall. Here is how to fix and winterize it.
Frozen pipes: thaw and prevent
A frozen pipe can split without warning. Here is how to thaw one safely and keep the next cold snap from catching you.
Why your water bill is high
A bill that jumps usually has a findable cause. Check the meter first, then the toilets.
Backflow device due for a test?
Phone in and tell us which type of device you have. A local contractor will be arranged.