Spot the Violation

PlumbingBackflow & cross-connectionsLevel 32018 UPC

Lawn irrigation connection at the house

Side of a house in summer, close to the ground: tan lap siding over an exposed concrete foundation, a mulch bed, and a mowed lawn. A 1 in. copper irrigation line comes out through the siding, turns up, and runs into a bronze pressure vacuum breaker assembly with a green canopy, two test cocks and blue-handled ball valves at each end, mounted about 2 ft above grade. On the outlet side the copper turns down toward the ground. Partway down, two small tubes connect the pipe to a white canister standing on a paver in the mulch, labeled as a fertilizer injector; then the line passes into the ground. An irrigation controller is mounted on the siding at right, and pop-up sprinkler heads sit flush in the flat lawn. LAWN FEED INJECTOR
Lawn irrigation supply where it leaves the house

What's wrong here?

  1. A fertilizer injector feeds the line downstream of a pressure vacuum breaker; a system with chemical injection needs a reduced-pressure principle assembly
  2. The pressure vacuum breaker must be at least 12 in. above the highest sprinkler head, and it is too low
  3. In Minnesota the irrigation backflow device has to be installed indoors so it will not freeze
  4. Nothing. This installation is compliant
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Show the answer and the code reference

The answer

A fertilizer (chemical) injector is connected to the irrigation piping, but the potable supply is protected only by a pressure vacuum breaker. A system with chemical injection requires a reduced-pressure principle backflow prevention assembly.

Correct choice: 1. A fertilizer injector feeds the line downstream of a pressure vacuum breaker; a system with chemical injection needs a reduced-pressure principle assembly

UPC 603.5.6 lets an irrigation system with no pumps and no chemical injection be protected by an atmospheric vacuum breaker, a pressure vacuum breaker, a spill-resistant vacuum breaker, or a reduced-pressure principle assembly. Where the system has a chemical injector or provisions for one, only a reduced-pressure principle (RP) assembly is allowed. A PVB handles backsiphonage of a low hazard (lawn water) but is not rated for backpressure and is not meant to keep a concentrated chemical out of the house water. A fertilizer canister in the line turns the whole irrigation system into a high hazard.

How to fix it

Replace the PVB with a reduced-pressure principle backflow prevention assembly, installed above grade where its relief port can discharge freely, and have it tested after installation and on the schedule the local authority requires. The other option is to remove the injector and cap the connection so there is no provision for chemical injection.

Code references

  • UPC 2018 603.5.6 — Protection from Lawn Sprinklers and Irrigation Systems

    Potable water supplies to irrigation systems that have no pumps or pumping connections and no chemical injection or provisions for chemical injection must be protected by an atmospheric vacuum breaker, a pressure vacuum breaker, a spill-resistant pressure vacuum breaker, or a reduced-pressure principle backflow preventer. Where a system has a chemical injector or provisions for chemical injection, the potable supply must be protected by a reduced-pressure principle backflow preventer.

    Drills citing 603.5.6

  • UPC 2018 603.1 — General

    Cross-connection control must be provided in accordance with Chapter 6. Equipment, mechanisms or substances that could pollute or contaminate the potable water supply are permitted only where the supply is protected by an approved backflow prevention device or assembly.

    Drills citing 603.1

Minnesota

MN status unverifiedConfidence: medium

Minnesota adopts the 2018 Uniform Plumbing Code with Minnesota amendments as the Minnesota Plumbing Code (Minn. Rules ch. 4714, effective Dec. 17, 2021). Minnesota amends parts of UPC section 603 (reportedly in Minn. Rules 4714.0603); whether it changes 603.5.6 was not confirmed. Minnesota water utilities and cities also run cross-connection programs that may require registration and annual testing of irrigation backflow assemblies; check ch. 4714 and the local water supplier.

About the Minnesota Plumbing Code

Why the other choices are wrong

  • The pressure vacuum breaker must be at least 12 in. above the highest sprinkler head, and it is too low. The 12 in. clearance for a PVB is a real rule, but this one sits about 2 ft above a flat lawn with flush pop-up heads. Height is not the problem; the device type is.
  • In Minnesota the irrigation backflow device has to be installed indoors so it will not freeze. PVBs are normally installed outdoors above grade and drained or blown out each fall. No rule requires them indoors, and because a PVB can spill water, outdoors is usually the better place.
  • Nothing. This installation is compliant. A PVB protects only against backsiphonage of lawn water. Once fertilizer is injected into the system, UPC 603.5.6 requires a reduced-pressure principle assembly.
Safety hazardLevel 3 · Master#irrigation#lawn sprinkler#pressure vacuum breaker#reduced pressure assembly#chemical injection#exterior

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