Backflow Prevention

Your irrigation system draws from the same line that supplies the house. A backflow prevention assembly is what keeps those two from mixing.

When pressure drops in the main — a hydrant opens, a line breaks, a pump shuts off — water can be pulled backward through the system. What comes back is whatever was sitting in the irrigation lines: fertilizer, ditch water, standing water in a valve box, and whatever has soaked into the ground around a cracked lateral. The assembly is the one component standing between that and the tap.

There are several types, and the one on your property was chosen for a reason — the hazard level, the water pressure, whether the device sits under continuous pressure, and what your water provider requires. The type also determines how it has to be tested and what it can be replaced with. The seven below are the ones we see on the Western Slope.

Device Types

Testable Assemblies

Pressure Vacuum Breaker (PVB)

The standard irrigation assembly on the Western Slope: a spring-loaded air inlet and a single check in one body, above ground near the point of connection, with a shutoff on each end and test cocks. Holds pressure all season, protects against suction only, and has to sit above the highest sprinkler head. Tested annually.

Double Check Valve Assembly (DCVA)

Two independent spring-loaded check valves in series, with a shutoff on each end and four test cocks. Protects against both suction and backpressure, and it is the one assembly that can be installed below grade in a vault. Approved for low-hazard connections only, never for a health hazard. Tested annually.

Reduced Pressure (RP)

Two checks with a relief valve between them, holding a middle chamber at lower pressure than the supply line. The highest protection available, and what is required wherever backflow would be a health hazard. It dumps water on the ground when it begins to fail, which is the design working rather than breaking. Tested annually.

Spill-Resistant Vacuum Breaker (SVB)

A pressure vacuum breaker built not to spit. A standard PVB discharges a little water through the air inlet each time the system starts up; this one seals before water reaches it. The protection is identical — suction only, no backpressure. Used indoors and anywhere a discharge would cause trouble. Tested annually.

Non-testable Assemblies

Atmospheric Vacuum Breaker (AVB)

The simplest device made: a body with an air inlet and a float, no test cocks and no shutoff valves. It cannot sit under constant pressure, and nothing may be installed downstream of it — which is why an irrigation system carries one per zone rather than one at the point of connection. Not testable.

Dual Check Valve (DuC)

Two check valves in one small body, with no shutoff valves and no test cocks, usually sitting at a residential meter. It is not the same thing as a double check valve assembly and will not satisfy a provider that requires one. Protects the street from your property, not your plumbing from itself. Not testable.

Hose Bibb Vacuum Breaker (HBVB)

The short brass fitting threaded onto an outdoor tap, between the faucet and the hose. The smallest and most common backflow device on any property, and the one most people have without knowing it is there. It breaks a siphon with air when the pressure drops, protects against suction only, and is defeated by any pump on the other end. Not testable.

What the assembly is protecting

There are seven device types on this page because there are a lot of different things that can be connected to a water line, and they are not equally dangerous. What determines which assembly belongs on a connection is two questions.

How bad is it if that water comes back? Water returning from a lawn is unpleasant. Water returning from a cooling tower or a chemical injector is a health hazard, and the rules treat those two very differently.

And can it come back under pressure? A vacuum breaker protects against suction — the backward pull when pressure drops in the main. It does nothing about a system that can push water back on its own. Anything with a pump, a boiler or elevated head is in the second category.

High hazard plus the ability to push is what calls for a reduced pressure assembly. Lower risk, or suction only, steps down from there. Your water provider makes the final call, because under Colorado's rules that decision belongs to them.

One more distinction matters, because it decides whether you get an annual bill. A testable assembly — reduced pressure, double check, pressure vacuum breaker, spill-resistant vacuum breaker — has test cocks and shutoff valves, and Colorado's annual test requirement applies to it. A non-testable device — an atmospheric vacuum breaker, a dual check, a hose bibb vacuum breaker — has no way to be checked in place. There is nothing to attach a gauge to. Those are inspected and replaced when they fail rather than tested and certified, and they are only permitted where the hazard is low enough to allow it.

Which of those two questions applies depends on what is connected. An irrigation system, a pool fill, a stock tank, a cooling tower and a dental chair are five different answers. What needs backflow protection, connection by connection — fourteen of them, and most properties have more than one.

What Colorado requires

Annual testing is not a preference your water provider happens to have. It comes out of Regulation 11, Section 11.39 of the Colorado Primary Drinking Water Regulations, administered by the state health department and substantially revised in August of 2020.

The rule is written against the water supplier rather than the property owner. Every public water system has to run a cross-connection control program and perform or verify annual testing on the assemblies in its service area. The system then passes that obligation along to its customers through ordinance or user agreement, which is why the paperwork looks different in Cedaredge than it does in Montrose while the underlying requirement does not change.

What does not vary:

  • Every testable assembly is tested once a year.
  • The test must be performed by a Certified Cross-Connection Control Technician, and the provider has to receive the report directly from the technician or their company. A copy handed to the customer does not satisfy the rule.
  • The report documents the assembly type, its location, make, model, serial number and size, the test date, the result, and the tester's certifying agency, certification number and expiration date.
  • Records are kept for three years.
  • A failed assembly has sixty days to be repaired or replaced and retested. If that does not happen, the supplier is required to suspend service or remove the cross-connection.

That last one is the part most people have not heard. A failed test is not a note in a file. It starts a clock, and the end of the clock is the water being shut off.

Who does the testing

Testing is performed by Todd Wellman, certified by the American Backflow Prevention Association, certification number 06-2512234. The report goes to your water provider directly from us, which is what the rule actually asks for.

We also keep the record of what is installed on your property — type, make, model, serial number, size and where it sits, assembly by assembly. The next test needs all of it, and an assembly that fails on a sixty-day clock is a considerably shorter conversation when somebody already knows what it is and what it can be replaced with.

When the test happens, and why it is not in the fall

An assembly can only be tested with water in it and pressure on it. That puts the test in the spring, after the system is charged — not in the fall, when it is being drained.

A winterization blowout is the opposite operation. The system is emptied, and the compressor is on a truck with a full route behind it. Holding that rig at the curb while an assembly is tested is not something we will do to the customers waiting further down the street, and the test would not be valid anyway on a system that is being taken apart.

So they are two visits at opposite ends of the season. Spring: startup and the annual test together, which is one trip and the right one. Fall: the blowout.

They also freeze

Most of these devices sit above ground with water standing in a brass body, and water expands when it freezes. The body splits, and a replacement costs several times what a blowout does.

It costs more than that, actually. A split assembly is discovered in the spring, at startup, which is the same visit as the annual test — so a freeze is a failed test, a sixty-day clock, and a replacement, all arriving in the same week of the busiest month of the year. Winterizing the system is the cheapest thing you can do to protect the assembly. We can take care of that in the fall.

Schedule a backflow test or call 970-835-9661