Why the backflow preventer is so vulnerable
Colorado irrigation systems connected to household water normally include a backflow prevention device so that lawn water cannot be drawn back into the drinking supply. On many Parker lots that device is a pressure vacuum breaker or a reduced pressure assembly standing above ground near the foundation, fed by a pipe that leaves the basement or crawl space through the wall.
It is made of brass and bronze castings with internal chambers that hold water, and it sits fully exposed to wind. When a hard freeze arrives before the system has been shut off and drained, the water inside expands and can crack the body, pop a bonnet, or split the copper riser. Parker sometimes sees its first hard freeze while lawns are still green, which is exactly when owners tend to put off winterizing.
The damage is usually outdoors, but not always. If the irrigation shutoff inside the house was left open, a split riser can push water back along the foundation, and a cracked line inside the wall can leak into a finished basement.
Where an irrigation freeze shows up
| Location | What failure looks like | Who usually handles it |
|---|---|---|
| Backflow device above ground | Water spraying from a cracked body or a bonnet that has lifted | Irrigation technician or plumber |
| Copper risers into the ground | Split along the pipe just above the soil line | Irrigation technician |
| Pipe through the foundation wall | Damp drywall or carpet on the inside of the wall near the device | Plumber, then drying if the interior is wet |
| Indoor irrigation shutoff and drain | Drip or seep at the valve in a mechanical room or under stairs | Plumber |
| Underground lines and valves | Soft, soggy patches or water bubbling up in spring | Irrigation technician |
Before a forecast hard freeze
Close the indoor irrigation valve
Find the shutoff where the irrigation line branches from household plumbing, usually in the basement or crawl space, and close it.
Drain what you can
Open the small drain or test cocks on the backflow device per its type so water can escape. If unsure, leave it to a technician.
Schedule the blowout
Compressed-air winterization clears the zones. It is commonly done by an irrigation company because too much pressure can damage parts.
Insulate if you must wait
An insulated bag over the device can buy a night or two, but it is not a substitute for draining.
Questions for an irrigation technician after a freeze
- Did the device body crack, or only a replaceable part such as a bonnet or poppet?
- Does the replacement need to be tested and the result reported to the water provider?
- Is the indoor shutoff holding fully, or does it seep when closed?
- Would an insulated enclosure or a different device location reduce the risk next fall?
- Is the pipe through the foundation wall sealed so cold air is not reaching indoor lines?
General information for Parker, not a quote or professional advice. In an emergency, call 911.